Abstract:
IR-transmitting alkaline earth selenogallo- and/or selenoindo-germanate glasses that are capable of hosting luminescent rare earth dopants. The relatively high Ga and/or In content of most compositions serves to eliminate the typical clustering tendency of rare earth dopants in chalcogenide glasses, resulting in improved luminescence.

Description:
This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 61/418,150 filed on Nov. 30, 2010 the content of which is relied upon and incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments relate generally to glass compositions and more particularly to infrared (IR) transmitting glasses useful for, for example, windows, waveguiding fibers, and/or host glasses for luminescent dopants. 
     2. Technical Background 
     U.S. Pat. No. 5,846,889 “Infrared Transparent Selenide Glasses” discloses alkaline earth Ga and/or In-containing selenogermanate glasses comprising at least 5% RSe (where R=alkaline earth), 0.5-25% Ga 2 Se 3  and/or In 2 Se 3 , 20-70% GeSe 2  with the provision for rare earth dopants. However, due to the relatively Ga- and/or In-poor nature of the compositions, it is likely that rare-earth dopants in such glasses are clustered and, therefore, characterized by reduced luminescent efficiency. 
     It would be advantageous to expand the range of BaGaGe selenide glasses that can be synthesized. Moreover, it would be advantageous to have “pergallous” glasses that may provide for a greater intensity/efficiency of rare earth luminescence. 
     SUMMARY 
     Embodiments of glass compositions have a Ga/Ba ratio greater than unity and such “pergallous” glasses are expected to provide for greater intensity/efficiency of rare earth luminescence. 
     Embodiments relate to infrared (IR) transmitting glasses that have potential application as IR windows, waveguiding fibers, or as host glasses for luminescent dopants, particularly rare earths, with emissions that are compromised by multiphonon decay in conventional oxide materials. Specifically, it relates to Ga- and/or In-containing chalcogenide glasses based on GeSe 2  that are modified by the presence of one or more alkaline earths, particularly Ba. 
     One embodiment is a glass composition comprising in mole percent:
         50 to 95 percent GeSe 2 ;   0.5 to 50 percent Ga 2 Se 3 , In 2 Se 3 , or a combination thereof; and   0.5 to 50 percent RSe, wherein R is an alkaline earth metal.       

     Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the invention as described in the written description and claims hereof. 
     It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. 
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the invention. 
     One embodiment is a glass composition comprising in mole percent:
         50 to 95 percent GeSe 2 ;   0.5 to 50 percent Ga 2 Se 3 , In 2 Se 3 , or a combination thereof; and   0.5 to 50 percent RSe, wherein R is an alkaline earth metal.       

     In one embodiment, the (Ga and/or In)/R ratio is greater than 1. 
     The glass composition according to some embodiments, comprises greater than 50 percent GeSe 2 , for example, greater than 55 percent GeSe 2 , for example, greater than 60 percent GeSe 2 , for example, greater than 65 percent GeSe 2 , for example, greater than 70 percent GeSe 2 , for example, greater than 71 percent GeSe 2 , for example, greater than 72 percent GeSe 2 , for example, greater than 73 percent GeSe 2 , for example, greater than 74 percent GeSe 2 , for example, greater than 75 percent GeSe 2 , for example, greater than 76 percent GeSe 2 . The amount of GeSe 2  can be any numerical value in the range of from 50 to 95 mole percent. 
     In one embodiment, the glass composition comprises more than one alkaline earth metal. In some embodiments, the alkaline earth metal is Ba, Sr, Ca, or combinations thereof. 
     In some embodiments, the glass composition comprises Ga 2 Se 3  and BaSe. The Ga/Ba ratio can be greater than 1. 
     The glass composition can comprise greater than 15 percent Ga 2 Se 3 , In 2 Se 3 , or a combination thereof, for example, greater than 16 percent, for example, greater than 17 percent, for example, greater than 18 percent, for example, greater than 19 percent, for example, greater than 20 percent, for example, greater than 21, for example, greater than 22 percent, for example, greater than 23 percent, for example, greater than 24 percent, for example, greater than 25 percent, for example, greater than 26 percent, for example, greater than 27 percent, for example, greater than 28 percent, for example, greater than 29 percent, for example, greater than 30 percent. The amount of Ga 2 Se 3 , In 2 Se 3 , or a combination thereof can be any numerical value in the range of from 0.5 to 50 mole percent. The glass in one embodiment comprises Ga 2 Se 3  and not In 2 Se 3 . The glass in one embodiment comprises In 2 Se 3  and not Ga 2 Se 3 . 
     The glass composition can further comprise one or more rare earth dopants, for example, 0 to 10 mole percent of the rare earth dopants, for example, greater than 0 to 10 mole percent of the rare earth dopants, for example, 0.5 to 10 mole percent of the rare earth dopants. The amount of rare earth dopants can be any numerical value in the range of from 0 to 10 mole percent. 
     The glass composition according to one embodiment comprises less than 37.5 percent RSe, for example, less than 35 percent, for example, less than 34 percent, for example, less than 33 percent, for example, less than 32.5 percent, for example, less than 30 percent, for example, less than 29 percent, for example, less than 28 percent, for example, less than 27 percent, for example, less than 26 percent, for example, less than 25 percent, for example, less than 24 percent, for example, less than 23 percent, for example, less than 22 percent, for example, less than 21 percent, for example, less than 20 percent, for example, less than 19 percent, for example, less than 18 percent, for example, less than 17 percent, for example, less than 16 percent, for example, less than 15 percent, for example, less than 14 percent, for example, less than 13 percent, for example, less than 12 percent, for example, less than 11 percent, for example, less than 10 percent, for example, less than 9 percent, for example, less than 8 percent, for example, less than 7 percent, for example, less than 6 percent, for example, less than 5 percent, for example, less than 4 percent, for example, less than 3 percent, for example, less than 2 percent. The amount of RSe can be any numerical value in the range of from 0.5 to 50 mole percent. In one embodiment, R is Ba. 
     The glass, in some embodiments, is transparent in the infra red spectrum. 
     The glass composition, according to some embodiments comprises:
         greater than 70 percent GeSe 2 ;   greater than 25 percent Ga 2 Se 3 , In 2 Se 3 , or a combination thereof; and   less than 29 percent RSe, wherein R is an alkaline earth metal.       

     The glass composition, according to some embodiments, comprises:
         greater than 70 percent GeSe 2 ;   greater than 25 percent Ga 2 Se 3 ; and   less than 29 percent BaSe.       

     The glass composition, according to some embodiments, comprises:
         greater than 65 percent GeSe 2 ;   greater than 15 percent Ga 2 Se 3 , In 2 Se 3 , or a combination thereof; and   less than 32.5 percent RSe, wherein R is an alkaline earth metal.       

     The glass composition, according to some embodiments, comprises:
         greater than 65 percent GeSe 2 ;   greater than 15 percent Ga 2 Se 3 ; and   less than 32.5 percent BaSe.       

     Significant expansion of the glassforming region of alkaline earth selenogermanate glasses allows for greater flexibility in tailoring glass properties such as characteristic temperatures (e.g. T g ), thermal expansion coefficient, refractive index, etc. that may be important for specific applications. Moreover, as noted above, the fact that the Ga and/or In to alkaline earth ratio is typically greater than one results in the efficient dispersal of rare earth dopants and, hence, improved luminescence. In addition, such “pergallous” and/or “perindous” glasses are expected to have superior chemical durability when compared to similar glasses with (Ga,In)/R&lt;1. Finally, as alkaline earth metals have a strong tendency to react with silica—the typical crucible material used for the preparation of chalcogenide glasses—“pergallous” and/or “perindous” melts have a reduced reaction tendency and, hence, the resultant glasses are expected to show no or insignificant oxide contamination which could limit their IR transparency. 
     The exemplary glasses were all prepared using typical chalcogenide glass melting/forming procedures. 10 g batches of elements (Ba, Ga, Ge, Se) were loaded into fused silica ampoules in a N 2 -filled glovebox. The ampoules were evacuated to ˜10 −5  Torr, flame sealed and then heated to ˜950° C. in a rocking furnace. After melting, the ampoules were quenched in room temperature water to convert the selenide melts to glass. Exemplary glass compositions are tabulated below, with the first rows expressing the composition in terms of the molar percentages of the various selenide components and with the second rows expressing the composition in terms of atomic percent. Although the alkaline earth in all cited examples is Ba, analogous glasses are to be expected when Ba is replaced by Sr and/or Ca. The glass transition temperature (T g ) and the onset of crystallization (T x ) were measured by differential scanning calorimetry (DSC). 
     Exemplary glass compositions are shown in Table 1, Table 2, Table 3, and Table 4. 
     
       
         
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Example 
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 mol % 
               
             
          
           
               
                 BaSe 
                 5 
                 7.5 
                 10 
                 12.5 
                 15 
                 17.5 
                 12.5  
                 15 
               
               
                 Ga 2 Se 3   
                 20 
                 17.5 
                 15 
                 12.5 
                 10 
                 7.5 
                 27.5 
                 25 
               
               
                 GeSe 2   
                 75 
                 75 
                 75 
                 75 
                 75 
                 75 
                 60 
                 60 
               
             
          
           
               
                   
                 atomic % 
               
             
          
           
               
                 Ba 
                 1.49  
                 2.29 
                 3.13 
                 4 
                 4.92 
                 5.88  
                 3.65 
                 4.48 
               
               
                 Ga 
                 11.94 
                 10.69 
                 9.38 
                 8 
                 6.56 
                 5.04  
                 16.06 
                 14.93 
               
               
                 Ge 
                 22.39 
                 22.9  
                 23.44 
                 24 
                 24.59 
                 25.21 
                 17.52 
                 17.91 
               
               
                 Se 
                 64.18 
                 64.12 
                 64.06  
                 64 
                 63.93 
                 63.87 
                 62.77 
                 62.69 
               
               
                 T g   
                 376 
                 382 
                 389 
                 396 
                 398 
                 395 
                 391 
                 391 
               
               
                 T x   
                 437 
                 443 
                 452 
                 466 
                 487 
                 484 
                 437 
                 443 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Example 
                 9 
                 10 
                 11 
                 12 
                 13 
                 14 
                 15 
                 16 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 mol % 
               
             
          
           
               
                 BaSe 
                 22.5 
                 25 
                 27.5 
                 30 
                 32.5 
                 10 
                 7.5 
                 20 
               
               
                 Ga 2 Se 3   
                 17.5 
                 15 
                 12.5 
                 10 
                 7.5 
                 30 
                 32.5 
                 5 
               
               
                 GeSe 2   
                 60 
                 60 
                 60 
                 60 
                 60 
                 60 
                 60 
                 75 
               
             
          
           
               
                   
                 atomic % 
               
             
          
           
               
                 Ba 
                 7.2 
                 8.2 
                 9.24  
                 10.34 
                 11.5  
                 2.86 
                 2.1 
                 6.9 
               
               
                 Ga 
                 11.2 
                 9.84 
                 8.4 
                 6.9 
                 5.31 
                 17.14 
                 18.18 
                 3.45 
               
               
                 Ge 
                 19.2 
                 19.67 
                 20.17 
                 20.69 
                 21.24 
                 17.14 
                 16.78 
                 25.86 
               
               
                 Se 
                 62.4 
                 62.3 
                 62.18 
                 62.07 
                 61.95 
                 62.86 
                 62.94 
                 63.79 
               
               
                 T g   
                 397 
                 400 
                 399 
                 397 
                 394 
                 378 
                 372 
                 395 
               
               
                 T x   
                 474 
                 480 
                 503 
                 500 
                 491 
                 427 
                 422 
                 481 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Example 
                 17 
                 18 
                 19 
                 20 
                 21 
                 22 
                 23 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 mol % 
               
             
          
           
               
                 BaSe 
                 15 
                 17.5 
                 5 
                 7.5 
                 5 
                 10 
                 15 
               
               
                 Ga 2 Se 3   
                 35 
                 27.5 
                 30 
                 27.5 
                 24 
                 19 
                 14 
               
               
                 GeSe 2   
                 55 
                 55 
                 65 
                 65 
                 71 
                 71 
                 71 
               
             
          
           
               
                   
                 atomic % 
               
             
          
           
               
                 Ba 
                 4.35 
                 5.19 
                 1.41 
                 2.16 
                 1.46 
                 3.05 
                 4.79 
               
               
                 Ga 
                 17.39 
                 16.3 
                 16.9  
                 15.83 
                 13.99 
                 11.59 
                 8.95 
               
               
                 Ge 
                 15.94 
                 16.3 
                 18.31 
                 18.71 
                 20.7 
                 21.65 
                 22.68 
               
               
                 Se 
                 62.32 
                 62.22  
                 63.38 
                 63.31 
                 63.85 
                 63.72 
                 63.58 
               
               
                 T g   
                   
                   
                   
                   
                 381 
                   
                 396 
               
               
                 T x   
                   
                   
                   
                   
                 440 
                   
                 467 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 Example 
                 24 
                 25 
                 26 
                 27 
                 28 
                 29 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 mol % 
               
             
          
           
               
                 BaSe 
                 20 
                 25 
                 4.99 
                 4.99 
                 17.49 
                 17.49 
               
               
                 Ga 2 Se 3    
                 9 
                 4 
                 20 
                 20 
                 7.5 
                 7.5 
               
               
                 GeSe 2    
                 71 
                 71 
                 74.97 
                 74.97 
                 74.97 
                 74.97 
               
               
                 Pr 2 Se 3   
                   
                   
                 0.05 
                   
                 0.04 
                   
               
               
                 Dy 2 Se 3   
                   
                   
                   
                 0.04 
                   
                 0.04 
               
             
          
           
               
                   
                 atomic % 
               
             
          
           
               
                 Ba 
                 6.71  
                 8.83 
                 1.49 
                 1.49 
                 5.88  
                 5.88 
               
               
                 Ga 
                 6.04 
                 2.83 
                 11.94 
                 11.94 
                 5.04  
                 5.04 
               
               
                 Ge 
                 23.83 
                 25.09 
                 22.38 
                 22.38  
                 25.2 
                 25.2 
               
               
                 Se 
                 63.42 
                 63.25 
                 64.17 
                 64.17 
                 63.85 
                 63.85 
               
               
                 Pr 
                   
                   
                 0.027 
                   
                 0.029 
                   
               
               
                 Dy 
                   
                   
                   
                 0.024 
                   
                 0.025 
               
               
                 T g   
                   
                   
                 377 
                 376 
                 396 
                 394 
               
               
                 T x   
                   
                   
                 437 
                 438 
                 484 
               
               
                   
               
             
          
         
       
     
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.