Patent Publication Number: US-2022228919-A1

Title: Infrared Transparent Constructs and Methods of Making Them

Description:
GOVERNMENT LICENSE RIGHTS 
     This invention was made with Government support under Contract No. N00178-04-D-4119-FC46 awarded by the United States Navy. The Government has certain rights in this invention. 
    
    
     BACKGROUND 
     Infrared radiation is electromagnetic energy within a portion of the electromagnetic spectrum that extends between the long wavelengths (red wavelengths) of the visible spectrum to the microwave wavelengths. Infrared radiation typically is considered to include radiation within the wavelength range of about 700 nanometers to about 1 millimeter. While generally not visible to the human eye, infrared radiation can be sensed by humans, e.g., as heat. Infrared radiation also can be detected electronically by infrared sensors or detection systems. 
     Infrared sensors and detection systems are used in a wide range of products and industries. Examples of such products include thermal imaging cameras, night vision goggles, remote controls, thermometers, guidance systems (e.g., for missiles), tracking systems, etc. 
     Products including infrared sensors and detection systems typically have their sensitive components protected within some type of housing or case. The infrared radiation, which typically originates from a source external to the product, must pass through the housing or case to reach the sensors and detection systems. In order to increase the intensity of infrared radiation incident on the sensors and detection systems, product housings or cases may include an infrared transparent construct (e.g., one or more structural elements, such as an infrared transparent window) through which the infrared radiation transmits prior to arriving at the sensors and detection systems. 
     SUMMARY 
     This Summary introduces a selection of concepts relating to this technology in a simplified form as a prelude to the Detailed Description that follows. This Summary is not intended to identify key or essential features. 
     Aspects of this disclosure relate to infrared transparent constructs, such as infrared transparent windows, methods of making them, and/or processes for making such constructs and/or products containing them. The infrared transparent constructs may be shaped as a dome (e.g., for an infrared detector system), window, and/or other desired geometries. In some more specific examples of this technology, the infrared transparent constructs may be formed as portions of IR seeker domes and/or windows for them. 
     Infrared transparent windows, e.g., for IR seeker domes or other products, may comprise: (a) a window base component including an interior surface and an exterior surface opposite the interior surface, wherein the window base component is comprised of an infrared transparent ceramic or plastic material; and (b) a first tracing at least partially located between the interior surface and the exterior surface. This first tracing may comprise an electrically conductive material, and at least 50% of a surface area or linear length of the first tracing may comprise an embedded tracing portion embedded in the window base component between the interior surface and the exterior surface. The first tracing in at least some examples of this technology may be formed as one of the following: electromagnetic interference shielding, a frequency selective surface grid, or an anti-static component. The infrared transparent windows may be made from “modular parts” (e.g., two independent window preform components) that are fixed together with the embedded tracing portion located between the preform components or as an “integral construction” (e.g., printed) with the embedded tracing portion included between printed layers. 
     These and other features of this technology are described in more detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some features of this technology are shown by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements. 
         FIGS. 1A, 1B, and 1C  provide examples of various shapes of infrared transparent constructs in accordance with aspects of this technology. 
         FIGS. 2A and 2B  provide a flow chart and illustrate various features of a method for producing infrared transparent constructs in accordance with some examples of this technology. 
         FIGS. 3A and 3B  provide a flow chart and illustrate various features of a modular method for producing infrared transparent constructs in accordance with some examples of this technology. 
         FIGS. 4A and 4B  provide side and cross sectional views, respectively, of an example infrared transparent construct produced by the method described in conjunction with  FIGS. 3A and 3B . 
         FIGS. 5A, 5B, and 5C  provide a flow chart and illustrate various features of a direct integration method for producing infrared transparent constructs in accordance with some examples of this technology. 
         FIGS. 6A and 6B  provide side and cross sectional views, respectively, of an example infrared transparent construct produced by the method described in conjunction with  FIGS. 5A, 5B, and 5C . 
         FIG. 7  illustrates an example of infrared transparent constructs in accordance with aspects of this technology incorporated into a final product and functioning as an infrared transparent window. 
     
    
    
     DETAILED DESCRIPTION 
     As described above, aspects of this technology relate to the structure of infrared transparent constructs (e.g., infrared transparent windows), e.g., of the types described above (and described in more detail), products containing such constructs, and methods of making constructs and products of the types described above (and described in more detail below). 
     The following specification uses various terms that are intended to have the meanings provided below unless otherwise specified or clear from the context. 
     “Infrared radiation,” as that term is used herein, means electromagnetic energy within the wavelength range of 700 nanometers (“nm”) to 1 millimeter (“mm”) of the electromagnetic spectrum. 
     An “infrared transparent” material, as that term is used herein, is a material that allows infrared radiation within at least a portion of the infrared spectrum incident on one surface of the material to pass through to the opposite surface of the material without substantial scattering and/or attenuation. In at least some examples of this technology, an “infrared transparent” material will allow at least 60% of incident infrared radiation within an infrared wavelength or wavelength range of interest to pass through it (and in some examples, at least 70%, at least 80%, at least 90%, at least 95%, or even at least 98% of incident infrared radiation within an infrared wavelength or wavelength range of interest will pass through it). The infrared transparency of a material may be affected by various physical properties, such as presence of doping materials and/or impurities, thickness, etc. Infrared transparent materials include, but are not necessarily limited to: zinc sulfide (ZnS, e.g., having a transmission range of about 0.37 to 14 microns); aluminum oxynitride (AlON, e.g., having a transmission range of about 0.25 to 6 microns); magnesium fluoride (MgF 2 , e.g., having a transmission range of about 0.13 to 7 microns); magnesium aluminate spinel (also called “spinel” herein, having a transmission range of about 0.25 to 6.5 microns); calcium fluoride (CaF 2 , e.g., having a transmission range of about 0.15 to 9.0 microns); gallium arsenide (GaAs, e.g., having a transmission range of about 1-15 microns); sodium chloride (NaCl, e.g., having a transmission range of about 0.2 to 20 microns); germanium (Ge, e.g., having a transmission range of about 2 to 17 microns); Schott BK7 glass (a borosilicate glass e.g., having a transmission range of 0.35 to 2.0 microns); fused silica UV grade or IR grade (SiO 2 , e.g., having a transmission range of 0.18 to 3.5 microns); lithium fluoride (LiF, e.g., having a transmission range of about 0.12 to 6.5 microns); quartz (SiO 2 , e.g., having a transmission range of about 0.15 to 3.3 microns); thallium bromoiodide (TIBr-TII, e.g., having a transmission range of about 0.6 to 40 microns); zinc selenide (ZnSe, e.g., having a transmission range of about 0.55 to 20 microns); and infrared transparent plastics (e.g., having a transmission range of about 8-12 microns and/or about 15-40 microns). Such infrared transparent materials are known and commercially available from various sources. 
     “Construct,” as that term is used herein, means any type of structural element of a product. In some examples, a “construct” will constitute an element of a housing or casing for a product (e.g., an exterior component of such housing or casing), such as a product that contains one or more infrared sensors or one or more infrared detection systems. 
     An “infrared transparent window,” as that term is used herein, is a “construct” or a portion thereof formed from an infrared transparent material. In some examples, “infrared transparent windows” may be provided in a product (e.g., in an overall construct of a product) for the purpose of transmitting infrared radiation to an infrared sensor or detection system provided as part of the product. Infrared transparent windows according to at least some aspects of this technology may have any desired shapes including flat, domed, hemispherical, curved, etc. Some aspects of this technology include infrared transparent windows and methods of making them in specific shapes, such as domed, hemispherical, curved, etc. Infrared transparent windows may have suitable structures and/or properties and/or may be suitably positioned with respect to one or more infrared sensors to “bend” the transmitted radiation to or toward a sensor or detection system (e.g., function as a lens or focusing component). 
     “Ultrafast high-temperature sintering,” as that term is used herein, means a sintering process that uses high heating rates (e.g., between 800° C./minute to 12000° C./minute), high cooling rates (e.g., between 800° C./minute to 12000° C./minute), and high sintering temperatures (e.g., between 1000° C. to 3000 C°). Examples of ultrafast high-temperature sintering processes that may be used in accordance with aspects of this technology are described in Wang, et al., “A General Method to Synthesize and Sinter Bulk Ceramics in Seconds,”  Science,  368, pp. 521-526 (2020), which article is entirely incorporated herein by reference. 
     At least some example sintering techniques used in methods according to aspects of this technology, including at least some examples of ultrafast high-temperature sintering techniques used according to aspects of this technology, may include one or more of the following: (a) increasing temperature of one or more heating elements forming a first heating surface and a second heating surface from a start temperature to a sintering temperature in 1 minute or less (and in some examples, in 45 seconds or less, or even 30 seconds or less); (b) isothermal sintering for a time period of less than 45 seconds (and in some examples, less than 40 seconds, less than 30 seconds, or even less than 25 seconds); and/or (c) after the sintering time period is complete, cooling the one or more heating elements forming the first heating surface and the second heating surface within a time period of less than 40 seconds (and in some examples, less than 30 seconds, less than 25 seconds, or even less than 20 seconds). The heating elements may comprise Joule-heating carbon strips, which are capable of producing temperatures of up to about 3000° C. The heating surfaces of the heating elements may be configured to or configurable to conform to the shape of the surface of the component being sintered. The heating rates, cooling rates, and/or sintering temperatures described in this specification correspond to the heating rates, cooling rates, and/or sintering temperatures of the heating elements used for the sintering process (e.g., the heating rates, cooling rates, and/or sintering temperatures of the heating element surfaces in contact with the part to be sintered). 
     The sintering processes used in any of the examples described herein may include laser assisted heating, e.g., using a laser to target areas for high heating and/or generally to increase heat applied for sintering. The sintering processes used in this technology may improve the mechanical properties of the sintered product, such as increasing its hardness, improving resistance to thermal and/or heat shock, etc. In some examples of this technology, initial heating can be performed using a laser and then an ultrafast high-temperature sintering process or other sintering process can be used on the preheated material to complete the sintering step (e.g., to form a more homogenous final product). 
       FIGS. 1A-1C  illustrate various example shapes of infrared transparent constructs (e.g., infrared transparent windows) in accordance with aspects of this technology.  FIG. 1A  shows a dome structure  100 . While not required, such dome structures  100  may be in the form of a hemisphere or other sectional portion of a sphere (also called a “spherical cap” or “spherical dome”). The dome structure  100  of this illustrated example includes an exterior surface  102  and an opposite interior surface  104  (the interior surface is shown by a broken line). An interior space within the dome structure  100  is exposed and accessible via opening  106 . If desired, the interior surface  104  may centered with and/or follow the same contour as the exterior surface  102 , e.g., thereby creating a constant wall thickness T (the thickness T is the shortest, most direct distance between the exterior surface  102  and the interior surface  104  at a given point). As a more specific example, each of the exterior surface  102  and interior surface  104  may be shaped as a spherical cap, and the surfaces  102 ,  104  may be oriented concentrically. Alternatively, if desired, the interior surface  104  and exterior surface  102  may have different shapes over at least some portion of their respective surface areas (e.g., thereby varying the wall thickness T). Dome structures  100  of this type may be well suited for various uses, such as infrared transparent windows for IR seekers on missiles or other projectiles. 
       FIG. 1B  shows another type of dome structure  120  for an infrared transparent construct (e.g., infrared transparent window). This illustrated example dome structure  120  has an exterior surface  122  that is curved over at least some portion of its surface area but not shaped as a section of a hemisphere. Exterior surfaces  122  of this type may be continuously curved, curved as a section of an ellipsoid or ovoid, curved in an arbitrary shape, curved in some portions and flat in others (e.g., curved around its side edge and flat, flattened, or less curved at its closed end and/or exposed face), etc. An interior surface  124  lies opposite the exterior surface  122 , and it may follow the same general contour as the exterior surface  122  (although this is not a requirement in all examples of this technology). The interior space within the dome structure  120  may be exposed and accessible via opening  126 . The wall thickness T (as defined above) may be constant or varied over at least some portion of the surface area of the dome structure  120  (e.g., depending on whether the interior surface  124  and exterior surface  122  follow the same general contour). 
     Another type of dome structure  140  for an infrared transparent construct (e.g., infrared transparent window) is shown in  FIG. 1C . The dome structure  140  of this illustrated example includes an exterior surface  142  and an opposite interior surface  144  that are hemi-cylindrically shaped and axially aligned. Alternatively, surfaces  142 ,  144  may be shaped to be a different sectional portion of cylinder. An interior space within the dome structure  140  is exposed and accessible via opening  146  (e.g., through the bottom and/or one or both sides). If desired, the interior surface  144  may be axially centered with and/or follow the same contour as the exterior surface  142 , e.g., thereby creating a constant wall thickness T (as defined above). Alternatively, if desired, the interior surface  144  and exterior surface  142  may have different shapes over at least some portion of their surface areas (e.g., thereby varying the wall thickness T). Shapes other than cylinder sections may be provided, such as sections of a conical shape, other axial elongated shapes, sections of an ellipsoid, sections of an ovoid, etc. 
     Building on the general structural information of infrared transparent windows in accordance with examples of this technology shown in  FIGS. 1A-1C , additional features of structures and methods in accordance with aspects of this technology now will be described in conjunction with  FIGS. 2A and 2B .  FIG. 2A  provides a general outline of steps in an infrared transparent construct production method in accordance with aspects of this technology and  FIG. 2B  illustrates some features of this method. As a first Step S 200  in this example process, a ceramic material powder, such as zinc sulfide, aluminum oxynitride, magnesium fluoride, and/or spinel, may be mixed in a ball mill with one or more organic solvents, such as isopropyl alcohol, ethanol, etc., for several hours, e.g., from 4 to 12 hours. This mixed material may then be dried at Step S 202 , e.g., in a conventional manner, such as in an oven at 200° C. for a sufficient time to reach a desired level of dryness (e.g., 1 hour to 12 hours). 
     Once dried, the ceramic material may be pressed and/or 3D printed into a desired shape for a window preform (Step S 204 ). When printed, any desired 3D printing process may be used, such as an aerosol jet method, an ink jet method, an extrusion method (e.g., paste extrusion), a fused deposition modeling method, a laser sintering method, etc. The ceramic material may be further processed in any appropriate manner to place it in a form suitable for use in the 3D printing process selected. 
     As a more specific example,  FIG. 2B  shows a two step process. First, an initial window preform  204  may be produced by a 3D printing process. While this initial window preform  204  may be printed directly into the final desired shape for the infrared transparent window product to be prepared, in this illustrated example it has a different, intermediate shape. This initial window preform  204  may then be further shaped in a pressing process between two pressing plates  206 . This step, when conducted, may further compress the powder and may further shape the initial window preform  204  into the final desired shape for the infrared transparent window product to be prepared or it may be formed into another intermediate shape. For example, at this Step S 204 , the initial window preform  204  may be pressed into a spherical cap shape, a cylindrical section shape, or other desired shape (e.g., as shown in  FIGS. 1A-1C ).  FIG. 2B  shows this example pressed window preform  208  from a top view, e.g., looking downward at a dome shape, such as a spherical cap (although any other shape may be provided for the pressed window preform  208 ). 
     Alternatively, if desired, the window preform  204  can be formed directly by printing the ceramic material into the desired shape and the pressing step can be omitted. As another alternative, if desired, the ceramic material can be pressed directly into the desired shape and the 3D printing step can be omitted. 
     Once the window preform  208  is prepared, at Step S 206 , one or more conductive tracings  210  may be printed on one or more of its surfaces  208 A (e.g., the interior surface  104 ,  124 ,  144  or exterior surface  102 ,  122 ,  142 ). This printing Step S 206  may be performed using any desired type of 3D printing process, such as an aerosol jet method, an ink jet method, an extrusion method (e.g., paste extrusion), etc. The conductive tracing(s)  210  may be printed in any desired shape(s) for performing any desired function(s). In some examples of this technology, the tracing(s)  210  (which may be continuous or discontinuous on the surface  208 A) may form at least a portion of: electromagnetic interference (“EMI”) shielding, a frequency selective surface (“FSS”) grid, an anti-static component, wiring to and/or from one or more electronic components and/or an electrical ground, etc. After any desired tracings  210  have been provided, the resulting combination of window preform  208  and tracings  210  may form window preform  212 . 
     In some examples of this technology, the “tracing(s)”  210  (and  310  and  410  described below) may include one or more segments or lines, e.g., akin to “wires,” having a longer length (dimension “L”) than their width dimension (dimension “W”) and/or thickness dimension (dimension “T”). A continuous tracing may comprise one or more segments that define a single path extending between a beginning and end of the tracing (e.g., a straight line path, a path with one or more curves, angles, and/or switchbacks, etc.) or may comprise one or more segments that define multiple paths (e.g., one or more branches, forks, etc.). A length (e.g., a linear length) of a tracing may comprise a sum of lengths of segments of that tracing. As some more specific examples, a tracing  210 / 310 / 410  may have a continuous length L at least 5 times greater than its width W and/or thickness T over at least 50% of the continuous length dimension. As still additional more specific examples, a tracing  210 / 310 / 410  may have a continuous length L at least 10 times greater, at least 15 times greater, at least 20 times greater, at least 25 times greater, at least 40 times greater, at least 50 times greater, at least 75 times greater, or even at least 100 times greater than its width dimension W and/or thickness dimension T over at least 50% of the continuous length dimension (and even over at least 75%, at least 80%, at least 90%, or even at least 95% of the continuous length dimension L). As some more absolute potential dimensions, one or more segments or lines of a tracing  210 / 310 / 410  may have width dimensions W of less than 2 inches (5.1 cm), and in some examples, less than 1.5 inches (3.8 cm), less than 1 inch (2.5 cm), less than 0.75 inch (1.9 cm), less than 0.5 inch (1.3 cm), or even less than 0.25 inch (0.6 cm) wide. Additionally or alternatively, as some further absolute potential dimensions, one or more segments or lines of a tracing  210 / 310 / 410  may have thickness dimensions T of less than 0.5 inch (1.3 cm), less than 0.25 inch (0.6 cm), or even less than 0.125 inch (0.3 cm) thick. All dimensions and/or dimension ratios described herein are merely examples, and dimensions and/or dimension ratios may be outside of any ranges associated with any such examples. For example, one or more segments or lines of a tracing  210 / 310 / 410  may have W dimensions outside of any ranges associated with the aforementioned examples and/or may have T dimensions outside of any ranges associated with the aforementioned examples. 
     In some examples, at least some (or some portion) of the tracing(s)  210 / 310 / 410  may be structured and sized with dimensions akin to conventional wiring on printed circuit board. The tracing  210 / 310 / 410  patterns may include two dimensional grids, hexagonal grids, circuit wiring, electronic component conductors etc. Commercially available conductive precursors are known in the art suitable for printing such conductive tracing(s)  210 / 310 / 410  (e.g., copper pastes, inks, and/or dyes available from Kuprion Inc.). 
     Window preform  212  may then be sintered in Step S 208 , e.g., using an ultrafast high-temperature sintering technique. In the sintering Step S 208 , window preform  212  may be placed between heating elements  214 A,  214 B within an inert atmosphere (e.g., a container filled with inert gas, such as argon), and the heating elements  214 A,  214 B may be heated and cooled (and the sintering otherwise also takes place) based on an ultrafast high-temperature sintering technique, as described above. The heating elements  214 A,  214 B may be made from carbon cloth or carbon paper (e.g., a Joule-heating carbon strip) attached to a glass slide or other silica based support material (e.g., a base support material that can remain stable and structurally sound under the sintering conditions). Heating element materials of this type (e.g., carbon cloth or carbon strips) are commercially available (e.g., from Fuel Cell Earth of Woburn, Mass.). A power supply may heat the heating elements  214 A,  214 B and may be controllable to control the temperature of the heating elements  214 A,  214 B, e.g., in conventional manners. 
       FIG. 2A  identifies Step S 208  as “conformal sintering.” “Conformal sintering,” as the term is used herein in this context, means that the sintering takes place using heating elements  214 A,  214 B that have surface shapes configured to or configurable to correspond to the surface of the shape being sintered. More specifically, in  FIG. 2B , heating element  214 A surface  216 A may be shaped the same shape as the shape of surface  208 A (which may correspond to one of the shapes of surface  102 ,  122 ,  142  for the window shapes shown in  FIGS. 1A-1C , respectively). Similarly, heating element  214 B surface  216 B may be shaped the same shape as the shape of surface  208 B (which may correspond to one of the shapes of surfaces  104 ,  124 ,  144  for the window shapes shown in  FIGS. 1A-1C , respectively). 
     In some examples of this technology, the part being sintered (as well as the final sintered part) may have an overall thickness of less than 4 inches (10.2 cm) thick (e.g., the dimension between the surfaces that the heating elements  214 A,  214 B contact) over at least 50% of the area located between the heating elements  214 A,  214 B. In further examples, the part being sintered will be less than 3.5 inches (8.9 cm), less than 3 inches (7.6 cm), less than 2.5 inches (6.4 cm), less than 2 inches (5.1 cm), less than 1.5 inches (3.8 cm), or even less than 1 inch (2.5 cm) thick (e.g., the dimension between the surfaces that the heating elements  214 A,  214 B contact) over at least 50% of the area located between the heating elements  214 A,  214 B. Any of these thickness ranges also may be present over at least 60%, at least 75%, at least 80%, at least 90%, or even at least 95% of the area located between the heating elements  214 A,  214 B. 
     If, when ready to start sintering Step S 208 , surface pair  208 A and  216 A and/or surface pair  208 B and  216 B is/are not the same shape, one or more actions can be taken to assure shape matching for the conformal sintering process. For example, before Step S 208 , an additional pressing and/or other shaping step can be performed on window preform  212  to change one or more of surface  208 A and/or  208 B shapes to correspond to the shapes of surface  216 A and/or  216 B. Additionally or alternatively, pressing force applied to window preform  212  by heating elements  214 A,  214 B may be sufficient to change the shape of surfaces  208 A and/or  208 B to correspond to the shapes of surfaces  216 A and/or  216 B, respectively. Additionally or alternatively, the surface(s)  216 A and/or  216 B of heating elements  214 A and  214 B, respectively, may be sufficiently deformable under conditions of use so that pressing force applied to window preform  212  by heating elements  214 A,  214 B may be sufficient to make the shape(s) of surfaces  216 A and/or  216 B conformable to the shapes of surfaces  208 A and/or  208 B, respectively. Preferably, during sintering Step S 208 , heating element  214 A surface  216 A will lie adjacent and in contact with surface  208 A and heating element  214 B surface  216 B will lie adjacent and in contact with surface  208 B. After sintering (and cooling), a final infrared transparent construct (e.g., window)  220  is formed. 
     If desired (e.g., depending on the ultimate target end use), e.g., after the sintering Step S 208  (and/or any other suitable time in the process), any further desired treatments and/or manufacturing steps (e.g., to incorporate the window  220  into a final product) may be completed (Step S 210 ). Such additional treatments may comprise one or more of: chemical vapor deposition treatment of one or more surfaces; sputtering processes; atomic layer deposition; transparency-enhancing or modifying treatments; hardness-enhancing or modifying treatments; etc. Such additional manufacturing steps may comprise: attachment of hardware components; electrically connecting to other components; further shaping; engagement in a detector system or other product; etc. 
     In the infrared transparent construct  220  structure and process described above, the electrically conductive tracing(s)  210  may be exposed on a surface  220 A of the construct  220 . While this can be acceptable for some applications and uses, it may have disadvantages in others. For example, infrared domes used in conventional seeker heads are constructed with conductive materials on the outside of the final product. These conductive materials can be quickly damaged and/or corroded, e.g., either in the typical environment of use and/or from use at high speeds at which missiles including seeker heads operate. Other conventional systems and methods involve use of a larger wire mesh on the inside of a dome head, but this arrangement tends to cause interference with infrared transparency. Some aspects of this technology seek to alleviate some of the issues with conventional seeker heads of these types. 
       FIGS. 3A and 3B  illustrate additional methods and structures in accordance with some aspects of this technology.  FIG. 3A  provides a flow chart of an example manufacturing method and  FIG. 3B  illustrates the structures of infrared transparent window preforms formed at various steps of this example method. As a first Step S 300  in this example process, a ceramic material powder, such as zinc sulfide, aluminum oxynitride, magnesium fluoride, and/or spinel, may be mixed in a ball mill with one or more organic solvents, such as isopropyl alcohol, ethanol, etc., for several hours, e.g., from 4 to 12 hours. This mixed ceramic material may be dried at Step S 302 , e.g., in a conventional manner, such as in an oven at 200° C. for a sufficient time to reach a desired level of dryness (e.g., 1 hour to 12 hours). 
     Once dried, the ceramic material may be pressed and/or 3D printed into a desired shape for a first window preform  304  (Step S 304 ). First window preform  304  also is referred to as an “interior window component” herein. To this point, the process may correspond to the processes described above with respect to Steps S 200  to S 204  and the production of window preforms  204  and/or  208  in conjunction with  FIGS. 2A and 2B . Further, any of the various features, options, and/or alternatives described above with respect to Steps S 200  to S 204  and the production of window preforms  204  and/or  208  may be used in the process of  FIGS. 3A and 3B  to produce first window preform  304 . Thus, much of the description of these similar process steps is omitted from this description of  FIGS. 3A and 3B . Alternatively, in some examples of this technology, rather than making window preform  304 , window preform  304  may be obtained as an existing product (e.g., an infrared transparent construct from a commercial source). 
     In addition to producing the first window preform  304 , the method of  FIGS. 3A and 3B  includes a Step S 306  of producing (e.g., printing and/or pressing) a second window preform  306  (second window preform  306  also is referred to as an “exterior window component” herein). The Step S 306  of producing the second window preform  306  may follow the same process(es) as those used to produce the first window preform  304  (and/or any of the steps, features, options, and/or alternatives described above with respect to Steps S 200  to S 204  and the production of window preforms  204  and/or  208 ). Alternatively, in some examples of this technology, rather than making window preform  306 , window preform  306  may be obtained as an existing product (e.g., an infrared transparent construct from a commercial source). Window preforms  304  and  306  may be produced such that the exterior surface  304 A of the first window preform  304  at least in part corresponds in shape with the interior surface  306 A of second window preform  306 . In some examples of this technology, at least 50% of the exterior surface  304 A area of first window preform  304  will correspond in shape to at least a portion of the interior surface  306 A of second window preform  306  (and in some examples, at least 60%, at least 75%, at least 80%, at least 90%, or even at least 95% of the exterior surface  304 A area of first window preform  304  will correspond in shape to at least a portion of the interior surface  306 A of second window preform  306 ). Additionally or alternatively, in at least some examples of this technology, at least 50% of the interior surface  306 A area of second window preform  306  will correspond in shape to at least a portion of the exterior surface  304 A of first window preform  304  (and in some examples, at least 60%, at least 75%, at least 80%, at least 90%, or even at least 95% of the interior surface  306 A of second window preform  306  will correspond in shape to at least a portion of the exterior surface  304 A of first window preform  304 ). The term “correspond in shape” as used herein in this context means that the two surface shapes will lie immediately adjacent and/or contact one another, e.g., when the window preforms  304  and  306  are oriented with surfaces  304 A and  306 A facing one another (e.g., stacked together), as will be described in more detail below. In some examples, surfaces  304 A and  306 A will “correspond in shape” by being spherically cap shaped of substantially the same diameter and arranged concentrically. 
     Once the first window preform  304  is prepared, at Step S 308 , one or more conductive tracings  310  may be printed on one or more of its surfaces, e.g., exterior surface  304 A in this illustrated example. This printing Step S 308  may be conducted using any desired type of 3D printing process, such as an aerosol jet method, an inkjet method, an extrusion method (e.g., paste extrusion), etc. Commercially available conductive precursors are known in the art suitable for printing such conductive tracing(s)  310 , as noted above. The conductive tracing(s)  310  may be printed in any desired shape(s) for performing any desired function(s). In some examples of this technology, the tracing(s)  310  (which may be continuous or discontinuous on the surface  304 A) may form at least a portion of: EMI shielding, an FSS grid, an anti-static component, wiring to and/or from one or more electronic components, wiring to an electrical ground, etc. After any desired tracings  310  have been provided, the resulting combination of window preform  304  and tracings  310  may form composite structure  312  (which also may be considered a window preform). 
     Additionally or alternatively, if desired, one or more conductive tracings  310  may be printed onto the interior surface  306 A of the exterior window preform  306 . Thickness dimension(s) T for one or more segments or lines of the tracing(s)  310  printed onto the first window preform  304  may be selected to facilitate arrangement of the composite structure  312  and the second window preform  306 , as described below. Also or alternatively, thickness dimension(s) T for one or more segments or lines of tracing(s)  310  printed onto the interior surface  306 A may be selected to facilitate similar arrangement of the composite structure  312  (or of the first window preform  304 ) and the second window preform  306 . 
     Composite structure  312  and second window preform  306  may then be arranged (e.g., stacked) so that the conductive tracing(s)  310  on the exterior surface  304 A of the first window preform  304  is/are covered by (and may be in contact with) the interior surface  306 A of second window preform  306 . This composite structure  320  (which also constitutes a window “preform”) is shown in  FIG. 3B  with the exterior surface  304 A of first window preform  304 , the interior surface  306 A of the second window preform, and the tracing(s)  310  shown as broken lines. First window preform  304  may be considered an “interior window component” and second window preform  306  may be considered an “exterior window component” as those terms are used herein. 
     In at least some examples of composite structure  320 , at least 50% of the exterior surface  304 A area of first window preform  304  will lie immediately adjacent and/or contact at least a portion of the interior surface  306 A of second window preform  306  (and in some examples, at least 60%, at least 75%, at least 80%, at least 90%, or even at least 95% of the exterior surface  304 A area of first window preform  304  will lie immediately adjacent and/or contact at least a portion of the interior surface  306 A of second window preform  306 ). Additionally or alternatively, in at least some examples of composite structure  320 , at least 50% of the interior surface  306 A area of second window preform  306  will lie immediately adjacent and/or contact at least a portion of the exterior surface  304 A of first window preform  304  (and in some examples, at least 60%, at least 75%, at least 80%, at least 90%, or even at least 95% of the interior surface  306 A of second window preform  306  will lie immediately adjacent and/or contact at least a portion of the exterior surface  304 A of first window preform  304 ). The conductive tracing(s)  310  may lie immediately adjacent and/or contact both exterior surface  304 A and interior surface  306 A over some of the conductive tracing surface area and/or linear length (and in at least some examples of composite structure  320 , at least 50% of the tracing(s)  310  surface area and/or linear length will lie immediately adjacent and/or contact one or both of the exterior surface  304 A of first window preform  304  and/or the interior surface  306 A of the second window preform  306  (and in some examples, at least 60%, at least 75%, at least 80%, at least 90%, or even at least 95% of the tracing(s)  310  surface area and/or linear length in the composite structure  320  will lie immediately adjacent and/or contact one or both of the exterior surface  304 A and/or the interior surface  306 A). In this manner, the conductive tracing(s)  310  (or at least any desired portion(s) thereof) is/are not externally exposed in the composite structure  320  and/or in the final window product (i.e., at least a portion of the tracing(s)  310  as described above are covered by second window preform  306  and/or sandwiched between the first window preform  304  and the second window preform  306 ). This layered or stacked construction helps protect the tracing(s)  310  in the remaining processing steps and in use. 
     The window preform comprising composite structure  320  may then be sintered as a single unit is Step S 312 , e.g., using an ultrafast high-temperature sintering technique in a conformal sintering process. In the sintering Step S 312 , composite structure  320  may be placed between heating elements  314 A,  314 B, and the heating elements  314 A,  314 B may be heated and cooled (and the sintering otherwise also takes place) based on an ultrafast high-temperature sintering technique, as described above. This conformal sintering Step S 312  may take place using: (a) one heating element  314 B having a surface  316 B configured to or configurable to correspond to the shape of at least a portion of the interior surface  304 B of the first window preform  304  (e.g., at least 50% of the area of interior surface  304 B) and (b) one heating element  314 A having a surface  316 A configured to or configurable to correspond to the shape of at least a portion of the exterior surface  306 B of the second window preform  306  (e.g., at least 50% of the area of exterior surface  306 B). Additionally or alternatively, in some examples of this technology, one of the heating elements  314 B may have a surface area that is configured to or configurable to contact a portion of the interior surface  304 B corresponding with the location(s) of the tracing(s)  310  and one of the heating elements  314 A may have a surface area that is configured to or configurable to contact a portion of the exterior surface  306 B corresponding with the location(s) of the tracing(s)  310 . Additionally or alternatively, in some examples of this technology, the heating elements  314 A and/or  314 B may have sufficient surface area at least to correspond to and sinter an area of the infrared transparent window that will be exposed to the external environment in the final product in which the infrared transparent window is placed. 
     If desired (e.g., depending on the ultimate target end use), e.g., after the sintering Step S 312  (and/or any other suitable time in the process), any further desired treatments and/or manufacturing steps (e.g., to incorporate the window  330  into a final product) may be completed (Step S 314 ). Such additional treatments may comprise one or more of: chemical vapor deposition treatment of one or more surfaces; sputtering processes; atomic layer deposition; transparency-enhancing or modifying treatments; hardness-enhancing or modifying treatments; etc. Such additional manufacturing steps may comprise: attachment of hardware components; electrically connecting to other components; further shaping; engagement in a detector system or other product; etc. 
       FIGS. 4A and 4B  provide side and sectional views, respectively, of an infrared transparent window  330  (or other construct) formed by the process described above in conjunction with  FIGS. 3A and 3B . As shown, the infrared transparent window  330  includes the two stacked components-reference number  334  identifies an interior window component that corresponds to the sintered version of first window preform  304  and reference number  336  identifies an exterior window component that corresponds to the sintered version of second window preform  306 . In the sintered infrared transparent window  330  product, however, components  334  and  336  are fixed together (e.g., as a result of the sintering process). The electrically conductive tracing(s)  310  is/are shown at an intermediate location between the outermost surface  336 A of the infrared transparent window  330  and the innermost surface  334 A of the infrared transparent window  330 . An open interior space  332  may be defined within the infrared transparent window  330  (and hardware components or other parts of a final product may be located at least partially within this open interior space  332 ). 
       FIGS. 4A and 4B  illustrate a boundary  338  at the interface of components  334  and  336  (in dot-dash lines). While such a distinct interface boundary may be present in the final infrared transparent window  330  product, this is not a requirement in all examples of this technology. In some examples of this technology, there may be no distinct boundary present at the interface of components  334  and  336  (i.e., there may be no discernible boundary interface corresponding to prior preform surfaces  304 A,  306 B present in the sintered infrared transparent window  330  product). In other words, the cross sectional structure may appear continuous through the thickness of the cross section (other than at the locations of the tracing(s)  310 ). The presence or absence of a discrete boundary  338  may depend, for example, on sintering conditions and/or other production processes. In at least some examples of this technology, the prior boundary interface corresponding to preform surfaces  304 A,  306 B will change to a substantially continuous crystalline structure as a result of the sintering process. 
       FIGS. 5A and 5B  provide diagrams of another method of forming infrared transparent windows (or other constructs) in accordance with aspects of this technology in which at least some portions of conductive tracing(s) (or other structures) is/are not exposed at the exterior surface of (and thus are protected within) the final product.  FIGS. 6A and 6B  provide side and sectional views, respectively, of an infrared transparent window  400  (or other construct) formed by the process described in conjunction with  FIGS. 5A and 5B . As a first Step S 400  in this example process, a ceramic material powder, such as zinc sulfide, aluminum oxynitride, magnesium fluoride, and/or spinel, may be mixed in a ball mill with one or more organic solvents, such as isopropyl alcohol, ethanol, etc., for several hours, e.g., from 4 to 12 hours. This mixed ceramic material may then be dried at Step S 402 , e.g., in a conventional manner, such as in an oven at 200° C. for a sufficient time to reach a desired level of dryness (e.g., 1 hour to 12 hours). To this point, the process may correspond to the processes described above with respect to Steps S 200  to S 202  and Steps S 300  to S 302  and the production of window preforms  204 ,  304 , and  306  in conjunction with  FIGS. 2A-3B . Further, any of the various features, options, and/or alternatives described above with respect to Steps S 200  to S 202  and/or Steps S 300  to S 302  may be used in the process of  FIGS. 5A and 5B . Thus, much of the description of these similar process steps is omitted from this description of  FIGS. 5A and 5B . 
     The ceramic material produced may be further treated into a form suitable for use as printing media material in a 3D printing process, such as printing media material for an aerosol jet method, an inkjet method, an extrusion method (e.g., paste extrusion), a fused deposition modeling method, a laser sintering method, etc. Then, at Step S 404 , a first portion  404  of a window preform may be printed. As some more specific examples, at this stage, the first portion  404  of the window preform may be printed into a desired shape, e.g., a shape shown in  FIGS. 1A-1C , but only 10% to 90% of an overall total thickness of the final window preform thickness is formed at this Step S 404 . In some examples, the first portion  404  of the printed window preform may be from 25% to 85%, from 35% to 80%, or from 45% to 75% of an overall total thickness of the final window preform to be produced in the printing process. 
     At Step S 406 , a pattern of conductive material (including one or more conductive tracing  410  segments) may be printed onto the surface  404 A of the first portion  404  of the window preform. This printing Step S 406  may be performed using any desired type of 3D printing process, such as an aerosol jet method, an ink jet method, an extrusion method (e.g., paste extrusion), etc. Surface  404 A onto which the tracing(s)  410  is/are printed also is called an “intermediate surface” herein. The tracing(s)  410  (which may be continuous or discontinuous on the intermediate surface  404 A) may form at least a portion of: EMI shielding, an FSS grid, an anti-static component, wiring to and/or from one or more electronic components, wiring to an electrical ground, etc. The resultant composite structure  406  including the first portion  404  and the tracing(s)  410  may be considered a window preform. 
     Then, at Step S 408 , a second portion  408  of the window preform is printed to at least partially cover the conductive tracing(s)  410  (tracing(s)  410  is/are shown in broken lines in the bottom of  FIG. 5B ). In at least some examples, the second portion  408  may cover at least 50% of the tracing(s)  410  surface area and/or linear length (and in some examples, at least 60%, at least 75%, at least 80%, at least 90%, or even at least 95% of the tracing(s)  410  surface area and/or linear length will be covered by second portion  408 ). In this manner, the conductive tracing(s)  410  (or at least any desired portion(s) thereof) are not externally exposed in the window preform  400  (i.e., desired portions of the tracing(s)  410  are covered by further printed layers in the overall printed window preform  400 ). This printed and layered construction will help protect the tracing(s)  410  in the remaining processing steps and in use. 
     In some examples, at Step S 408 , the second portion  408  of the window preform may be printed to create the exterior surface  408 B into a desired shape, e.g., a shape shown in  FIGS. 1A-1C , and to form a remainder of an overall total thickness of the final window preform thickness (e.g., the remainder of the window preform  400  may be printed at Step S 408 ). Alternatively, as shown in Step S 410 , if desired, additional conductive pattern tracing(s) and/or additional overlaying printed layers may be printed to form the final window preform  400 . Multiple steps of printing conductive tracing(s) in different layers of the final window preform  400  may be used, e.g., to place conductive tracing(s) at different relative positions in the overall final window preform, to form more than one component in the final window preform (e.g., two or more of EMI shielding, an FSS grid, an anti-static component, wiring to and/or from one or more electronic components, wiring to an electrical ground, etc.), etc. For example, as shown in  FIG. 5C  (a vertical partial section of the view shown in the circled area in  FIG. 5B ): (a) one tracing segment layer  410 A may be printed on the intermediate surface (e.g.,  404 A) of the first portion  404  of the window preform when it is at a thickness of T 1 , (b) the second portion  408  of the window preform may be printed on top of the first portion  404  and (at least partially) covering tracing segment layer  410 A, (c) another tracing segment layer  410 B may be printed on the intermediate surface of the second portion  408  of the window preform when it is at thickness T 2 , and (d) one or more additional layers  412  of the window preform (and/or one or more additional tracing  410  segments) may be printed on top of the second portion  408  and (at least partially) covering tracing segment layer  410 B). 
     At Step S 412 , the window preform  400 —including the conductive tracing(s)  410  at least partially embedded within the printed window preform  400  body—may be pressed into a desired final shape and/or to compact the structure. This pressing Step S 412 , when present, may alter the thickness of the printed window preform  400 . 
     Once the window preform  400  is prepared (and in some examples pressed and/or further treated), the composite structure of the window preform  400  may be sintered S 414 , e.g., using an ultrafast high-temperature sintering technique in a conformal sintering process. In the sintering Step S 414 , window preform  400  may be placed between heating elements, and the heating elements may be heated and cooled (and the sintering otherwise also takes place) based on an ultrafast high-temperature sintering technique, as described above in conjunction with  FIGS. 3A and 3B . This conformal sintering Step S 414  may take place using: (a) one heating element configured to or configurable to correspond to the shape of at least a portion of the interior surface  404 B of the window preform  400  (e.g., at least 50% of the area of interior surface  404 B) and (b) one heating element configured to or configurable to correspond to the shape of at least a portion of the exterior surface  408 B of the window preform  400  (e.g., at least 50% of the area of exterior surface  408 B). Additionally or alternatively, in some examples of this technology, one of the heating elements may have a surface area that is configured to or configurable to contact a portion of the interior surface  404 B corresponding with the location(s) of the tracing(s)  410  and one of the heating elements may have a surface area that is configured to or configurable to contact a portion of the exterior surface  408 B corresponding with the location(s) of the tracing  410  segments. Additionally or alternatively, in some examples of this technology, the heating elements may have sufficient surface area at least to correspond to and sinter an area of the infrared transparent window that will be exposed to the external environment in the final product in which the infrared transparent window is placed. Heating elements of the types described with respect to and illustrated in  FIGS. 3A and 3B  may be used in sintering Step S 414 . 
     If desired (e.g., depending on the ultimate target end use), e.g., after the sintering Step S 414  (and/or any other suitable time in the process), any further desired treatments and/or manufacturing steps (e.g., to incorporate the window into a final product) may be completed (Step S 416 ). Such additional treatments may comprise one or more of: chemical vapor deposition treatment of one or more surfaces; sputtering processes; atomic layer deposition; transparency-enhancing or modifying treatments; hardness-enhancing or modifying treatments; etc. Such additional manufacturing steps may comprise: attachment of hardware components; electrically connecting to other components; further shaping; engagement in a detector system or other product; etc. 
       FIGS. 6A and 6B  provide side and sectional views, respectively, of an infrared transparent window  600  (or other construct) formed by the process described above in conjunction with  FIGS. 5A and 5B . As shown, the infrared transparent window  600  includes the conductive tracing(s)  410  embedded within the interior  600 B of the continuous printed structure (the continuous printed structure also may constitute a “window base component” as that term is used herein) forming the infrared transparent window  600 . The infrared transparent window  600  of this example may be seamless. The tracing(s)  410  is/are shown in broken lines in  FIG. 6A  because they are not exposed at the exterior surface  600 A of this example infrared transparent window  600 . An open interior space  602  may be defined within the infrared transparent window  600  (and hardware components or other parts of a final product may be located at least partially within this open interior space  602 ). 
       FIG. 7  illustrates an infrared detection system  700 , such as a thermal imaging camera, night vision goggles, a remote control, a thermometer, a guidance system (e.g., for missiles), an infrared seeker, etc., in accordance with some aspects of this technology. The infrared detection system  700  includes a housing  702  or other structure for supporting one or more infrared sensors  704  (e.g., sensor(s)  704  may be mounted on a base  706  supported within the housing  702  and facing window  330 ,  600 ). Such infrared sensor(s)  704 , including sensor arrays, are commercially available and known in the art. In this illustrated example, one end of the infrared detection system  700  includes an infrared transparent window  330 ,  600  in accordance with aspects of this technology, e.g., of the types described above. The infrared transparent window  330 ,  600  forms an exposed surface  700 A of the infrared detection system  700 , and it is positioned and configured to transmit at least some infrared radiation  710  incident on the exposed surface  700 A to the infrared sensor(s)  704 . Optionally, if desired, the infrared transparent window  330 ,  600  may be shaped and/or positioned with respect to the infrared sensor(s)  704  to “bend” incoming radiation  710  in a direction to become incident on the infrared sensor(s)  704  (akin to the manner in which an optical lens “bends” visible light). 
     As shown in  FIG. 7 , infrared radiation  710  emitted from an object  712  (e.g., an object to be tracked, a target for a missile or other projectile, etc.) is incident on the exposed surface  700 A of the detection system  700  (on the exterior surface of infrared transparent window  330 ,  600 ). At least some portion of the incident radiation  710  (e.g., one or more infrared wavelengths or infrared wavelength bands) passes through the infrared transparent window  330 ,  600 . In this manner the infrared transparent window  330 ,  600  is transparent to at least some portion of the incident radiation  710  (e.g., one or more wavelengths or wavelength bands), shown by reference number  710 A in  FIG. 7 . Once inside, this portion  710 A of the radiation transmits to the infrared sensor(s)  704 . The sensor(s)  704  may provide output data  714  to one or more other electronic components  716  located internal to and/or external to the housing  702 . The data  714  may be used for any desired purpose. For example, infrared detection systems  700  may provide input data to a thermal camera, other imaging system(s), tracking systems, guidance systems, etc., including electronic components  716  as are conventionally known and commercially available. 
     Some example aspects of this technology may start with an existing infrared transparent construct (e.g., a commercially available infrared transparent dome and/or infrared transparent window) to which a hardened infrared transparent construct is applied according to aspects of this technology. As a more specific example, returning to the example processes described above in conjunction with  FIGS. 5A-6B , rather than completing steps S 400 , S 402 , and S 404 , the first portion  404  of the window preform may be obtained as an existing product (e.g., from a commercial source). Step S 406  (printing conductive tracing(s)  410 ) may be performed, e.g., if such tracing(s)  410  are needed in the product being formed and/or if such tracing(s)  410  are not already present on the first portion  404 . Then, Step S 408  may be performed to form a new layer of an infrared transparent construct (e.g., second portion  408  of the window preform) on the first portion  404  (and over any previously present and/or newly added tracing(s)  410 ). Steps S 410  and/or S 412  also can be performed, e.g., if required in the desired product. Then conformal sintering of the combined “existing product” first portion  404  and the newly printed second portion  408  can be completed (Step S 414 ). Any further treatments (S 416 ) also can be completed, if needed for the desired final product. In this manner, in accordance with at least some examples of this aspect of the technology, a hardened “coating” or layer can be formed on an existing infrared transparent construct product. This process could be used, for example, to retrofit existing products with a hardened layer (and thus potentially make those products more suitable for use in different applications). 
     While some of the illustrated examples of this technology relate to infrared transparent constructs in the form of conformal domes, aspects of this technology can be applied to providing infrared transparent constructs of a wide variety of shapes, including: shapes in which the interior surface and/or the exterior surface is/are a non-planar surface; shapes in which the interior surface and/or the exterior surface is/are shaped as a section of a sphere; shapes in which the interior surface and/or the exterior surface is/are shaped as a section of a cylinder; shapes in which the interior surface and/or the exterior surface have substantially the same shape and/or follow substantially the same general contour; shapes in which the interior surface and/or the exterior surface is/are arranged concentrically; shapes in which the interior surface and/or the exterior surface is/are planar; have shapes that form a window having a constant thickness; have shapes that form a window having differing thickness; etc. Alternatively, if desired, the interior surface and the exterior surface may be shaped different from one another and/or given a non-standard shape. 
     CONCLUSION 
     For the avoidance of doubt, the present application includes, but is not limited to, the subject-matter described in the following numbered clauses: 
     Clause 1. An infrared transparent window, comprising:
         a window base component including an interior surface and an exterior surface opposite the interior surface, wherein the window base component is comprised of an infrared transparent ceramic or plastic material; and   a first tracing comprising an electrically conductive material, wherein optionally at least 50% of a surface area or linear length of the first tracing comprises an embedded tracing portion embedded in the window base component between the interior surface and the exterior surface.       

     Clause 2. The infrared transparent window according to Clause 1, wherein each of the interior surface and the exterior surface is a non-planar surface. 
     Clause 3. The infrared transparent window according to Clause 1, wherein each of the interior surface and the exterior surface is shaped as a section of a sphere. 
     Clause 4. The infrared transparent window according to Clause 1, wherein each of the interior surface and the exterior surface is dome shaped. 
     Clause 5. The infrared transparent window according to any one of Clauses 1 to 4, wherein the infrared transparent ceramic or plastic material includes at least one member selected from the group consisting of zinc sulfide, aluminum oxynitride, magnesium fluoride, and spinel. 
     Clause 6. The infrared transparent window according to any one of Clauses 1 to 5, wherein the infrared transparent window comprises an infrared seeker dome. 
     Clause 7. The infrared transparent window according to any one of Clauses 1 to 6, wherein the first tracing is formed as one of the following: electromagnetic interference shielding, a frequency selective surface grid, or an anti-static component. 
     Clause 8. The infrared transparent window according to any one of Clauses 1 to 7, wherein the window base component comprises: (a) a first window component forming the interior surface and a first intermediate surface opposite the interior surface, and (b) a second window component forming the exterior surface and a second intermediate surface opposite the exterior surface, wherein the first intermediate surface faces and contacts the second intermediate surface, and wherein the embedded tracing portion is located between and in contact with the first intermediate surface and the second intermediate surface. 
     Clause 9. The infrared transparent window according to any one of Clauses 1 to 7, wherein the window base component comprises a printed component forming the interior surface and the exterior surface, and wherein the embedded tracing portion is a printed structure printed between and spaced from the interior surface and the exterior surface. 
     Clause 10. An infrared transparent window, comprising:
         an interior window component having an interior surface and an exterior surface, wherein the interior window component comprises a first infrared transparent ceramic or plastic material;   an exterior window component having an interior surface and an exterior surface, wherein at least a portion of the interior surface of the exterior window component contacts the exterior surface of the interior window component to form a contacting surface portion of the infrared transparent window, and wherein the exterior window component comprises the first infrared transparent ceramic or plastic material or a second infrared transparent ceramic or plastic material that differs from the first infrared transparent ceramic or plastic material; and   a first tracing at least partially located between the exterior surface of the interior window component and the interior surface of the exterior window component, wherein the first tracing comprises an electrically conductive material, and wherein optionally at least a portion of a surface area or linear length of the first tracing contacts both the exterior surface of the interior window component and the interior surface of the exterior window component.       

     Clause 11. The infrared transparent window according to Clause 10, wherein each of the exterior surface of the interior window component and the interior surface of the exterior window component is a non-planar surface. 
     Clause 12. The infrared transparent window according to Clause 10, wherein each of the exterior surface of the interior window component and the interior surface of the exterior window component at the contacting surface portion is shaped as a section of a sphere. 
     Clause 13. The infrared transparent window according to Clause 10, wherein each of the exterior surface of the interior window component and the interior surface of the exterior window component at the contacting surface portion is dome shaped. 
     Clause 14. The infrared transparent window according to any one of Clauses 10 to 13, wherein the first infrared transparent ceramic or plastic material includes at least one member selected from the group consisting of zinc sulfide, aluminum oxynitride, magnesium fluoride, and spinel. 
     Clause 15. The infrared transparent window according to any one of Clauses 10 to 14, wherein the exterior window component comprises the second infrared transparent ceramic or plastic material. 
     Clause 16. The infrared transparent window according to Clause 15, wherein the second infrared transparent ceramic or plastic material includes at least one member selected from the group consisting of zinc sulfide, aluminum oxynitride, magnesium fluoride, and spinel. 
     Clause 17. The infrared transparent window according to any one of Clauses 10 to 16, wherein the portion of the surface area or linear length of the first tracing that contacts both the exterior surface of the interior window component and the interior surface of the exterior window component includes at least 50% of the surface area or linear length of the first tracing. 
     Clause 18. The infrared transparent window according to any one of Clauses 10 to 17, wherein the infrared transparent window comprises an infrared seeker dome. 
     Clause 19. The infrared transparent window according to any one of Clauses 10 to 18, wherein the first tracing is formed as one of the following: electromagnetic interference shielding, a frequency selective surface grid, or an anti-static component. 
     Clause 20. An infrared transparent window, comprising:
         a window base component printed to include an interior surface and an exterior surface as a unitary, one-piece structure, wherein the window base component comprises a first infrared transparent ceramic or plastic material; and   a first printed tracing embedded within the first infrared transparent ceramic or plastic material and located between the interior surface and the exterior surface of the window base component, wherein the first printed tracing comprises an electrically conductive material.       

     Clause 21. The infrared transparent window according to Clause 20, wherein each of the exterior surface and the interior surface of the window base component is a non-planar surface. 
     Clause 22. The infrared transparent window according to Clause 20, wherein at least a portion of the exterior surface of the window base component is shaped as a section of a sphere. 
     Clause 23. The infrared transparent window according to Clause 20, wherein at least a portion of the exterior surface of the window base component is dome shaped. 
     Clause 24. The infrared transparent window according to any one of Clauses 20 to 23, wherein the first infrared transparent ceramic or plastic material includes at least one member selected from the group consisting of zinc sulfide, aluminum oxynitride, magnesium fluoride, and spinel. 
     Clause 25. The infrared transparent window according to any one of Clauses 20 to 24, wherein the infrared transparent window comprises an infrared seeker dome. 
     Clause 26. The infrared transparent window according to any one of Clauses 20 to 25, wherein the first printed tracing is formed as one of the following: electromagnetic interference shielding, a frequency selective surface grid, or an anti-static component. 
     Clause 27. An infrared detection system, comprising:
         a housing;   one or more infrared sensors mounted within the housing; and   an infrared transparent window according to any one of Clauses 1 to 26 forming an exposed surface of the infrared detection system, wherein the infrared transparent window is positioned and configured to transmit at least some infrared radiation incident on the exposed surface to the one or more infrared sensors.       

     Clause 28. A method of forming an infrared transparent window, comprising:
         forming an interior window component having an interior surface and an exterior surface, wherein the interior window component comprises a first infrared transparent ceramic or plastic material;   forming an exterior window component having an interior surface and an exterior surface, wherein the exterior window component comprises the first infrared transparent ceramic or plastic material or a second infrared transparent ceramic or plastic material that differs from the first infrared transparent ceramic or plastic material;   forming a first tracing on one of the exterior surface of the interior window component or the interior surface of the exterior window component, wherein the first tracing comprises an electrically conductive material;   engaging the interior window component with the exterior window component such that at least a portion of the exterior surface of the interior window component contacts the interior surface of the exterior window component at a contact surface portion and such that at least a portion of a surface area or linear length of the first tracing contacts both the exterior surface of the interior window component and the interior surface of the exterior window component.       

     Clause 29. The method according to Clause 28, wherein each of the exterior surface of the interior window component and the interior surface of the exterior window component is formed as a non-planar surface. 
     Clause 30. The method according to Clause 28, wherein each of the exterior surface of the interior window component and the interior surface of the exterior window component at the contacting surface portion is formed in a shape as a section of a sphere. 
     Clause 31. The method according to Clause 28, wherein each of the exterior surface of the interior window component and the interior surface of the exterior window component at the contacting surface portion is formed in a dome shape. 
     Clause 32. The method according to any one of Clauses 28 to 31, wherein the first infrared transparent ceramic or plastic material includes at least one member selected from the group consisting of zinc sulfide, aluminum oxynitride, magnesium fluoride, and spinel. 
     Clause 33. The method according to any one of Clauses 28 to 32, wherein the exterior window component comprises the second infrared transparent ceramic or plastic material. 
     Clause 34. The method according to Clause 33, wherein the second infrared transparent ceramic or plastic material includes at least one member selected from the group consisting of zinc sulfide, aluminum oxynitride, magnesium fluoride, and spinel. 
     Clause 35. The method according to any one of Clauses 28 to 34, wherein the portion of the surface area or linear length of the first tracing that contacts both the exterior surface of the interior window component and the interior surface of the exterior window component includes at least 50% of the surface area or linear length of the first tracing. 
     Clause 36. The method according to any one of Clauses 28 to 35, wherein the step of forming the interior window component includes printing the first infrared transparent ceramic or plastic material. 
     Clause 37. The method according to any one of Clauses 28 to 36, wherein the step of forming the interior window component includes pressing the first infrared transparent ceramic or plastic material into a different shape. 
     Clause 38. The method according to any one of Clauses 28 to 37, wherein the step of forming the exterior window component includes printing the first infrared transparent ceramic or plastic material or the second infrared transparent ceramic or plastic material. 
     Clause 39. The method according to any one of Clauses 28 to 38, wherein the step of forming the exterior window component includes pressing the first infrared transparent ceramic or plastic material or the second infrared transparent ceramic or plastic material into a different shape. 
     Clause 40. The method according to any one of Clauses 28 to 39, wherein the step of forming the first tracing includes printing the electrically conductive material on one of the exterior surface of the interior window component or the interior surface of the exterior window component. 
     Clause 41. The method according to any one of Clauses 38 to 40, wherein after the engaging step, the interior window component and the exterior window component form a composite window component, and wherein the method further includes sintering the composite window component in a heating system. 
     Clause 42. The method according to Clause 41, wherein the heating system includes a first heating surface configured or configurable to contact at least a portion of the interior surface of the interior window component and a second heating surface configured or configurable to contact at least a portion of the exterior surface of the exterior window component. 
     Clause 43. The method according to Clause 41 or 42, wherein the sintering step utilizes an ultrafast high-temperature sintering technique. 
     Clause 44. The method according to Clause 41 or 42, wherein the sintering step includes increasing temperature of one or more heating elements forming the first heating surface and the second heating surface from a start temperature to a sintering temperature in 1 minute or less. 
     Clause 45. The method according to any one of Clauses 41, 42, or 44, wherein the sintering step includes isothermal sintering for a time period of less than 30 seconds. 
     Clause 46. The method according to any one of Clauses 41, 42, 44, or 45, wherein after sintering is complete, the method includes cooling within a time period of less than 20 seconds. 
     Clause 47. The method according to any one of Clauses 28 to 46, wherein the step of forming the first tracing forms the first tracing as one of the following: electromagnetic interference shielding, a frequency selective surface grid, or an anti-static component. 
     Clause 48. An infrared transparent window made by the method according to any one of Clauses 28 to 47. 
     Clause 49. An infrared seeker dome including an infrared transparent window made by the method according to any one of Clauses 28 to 47. 
     Clause 50. A method of forming an infrared transparent window, comprising:
         printing a first infrared transparent ceramic or plastic material to form an intermediate window base component that includes an interior surface and an intermediate surface;   printing an electrically conductive material to form a first tracing on the intermediate surface; and   printing the first infrared transparent ceramic or plastic material to form a window base component having an exterior surface, wherein in the window base component, the first infrared transparent ceramic or plastic material is printed to contact and at least partially cover the intermediate surface and to contact and at least partially cover the first tracing.       

     Clause 51. The method according to Clause 50, wherein each of the interior surface and the exterior surface is a non-planar surface. 
     Clause 52. The method according to Clause 50, wherein at least a portion of the exterior surface of the window base component is shaped as a section of a sphere. 
     Clause 53. The method according to Clause 50, wherein at least a portion of the exterior surface of the window base component is dome shaped. 
     Clause 54. The method according to any one of Clauses 50 to 53, wherein the first infrared transparent ceramic or plastic material includes at least one member selected from the group consisting of zinc sulfide, aluminum oxynitride, magnesium fluoride, and spinel. 
     Clause 55. The method according to any one of Clauses 50 to 54, further comprising pressing at least one of the intermediate window base component or the window base component to change a shape thereof. 
     Clause 56. The method according to any one of Clauses 50 to 55, wherein after the step of printing the first infrared transparent ceramic or plastic material to form the window base component, the method further includes sintering the window base component in a heating system. 
     Clause 57. The method according to Clause 56, wherein the heating system includes a first heating surface configured or configurable to contact at least a portion of the interior surface and a second heating surface configured or configurable to contact at least a portion of the exterior surface. 
     Clause 58. The method according to Clause 56 or 57, wherein the sintering step utilizes an ultrafast high-temperature sintering technique. 
     Clause 59. The method according to Clause 56 or 57, wherein the sintering step includes increasing temperature of one or more heating elements forming the first heating surface and the second heating surface from a start temperature to a sintering temperature in 1 minute or less. 
     Clause 60. The method according to any one of Clauses 56, 57, or 59, wherein the sintering step includes isothermal sintering for a time period of less than 30 seconds. 
     Clause 61. The method according to any one of Clauses 56, 57, 59, or 60, wherein after sintering is complete, the method includes cooling within a time period of less than 20 seconds. 
     Clause 62. The method according to any one of Clauses 50 to 61, wherein the step of printing the electrically conductive material forms the first tracing as one of the following: electromagnetic interference shielding, a frequency selective surface grid, or an anti-static component. 
     Clause 63. An infrared transparent window made by the method according to any one of Clauses 50 to 62. 
     Clause 64. An infrared seeker dome including an infrared transparent window made by the method according to any one of Clauses 50 to 62. 
     The foregoing has been presented for purposes of example. The foregoing is not intended to be exhaustive or to limit features to the precise form disclosed. The examples discussed herein were chosen and described in order to explain principles and the nature of various examples and their practical application to enable one skilled in the art to use these and other implementations with various modifications as are suited to the particular use contemplated. The scope of this disclosure encompasses, but is not limited to, any and all combinations, subcombinations, and permutations of structure, operations, and/or other features described herein and in the accompanying drawing figures.