Proceedings of the 10th DoD Electromagnetic Windows Symposium 

Norfolk, Virginia, May 2004 

A Century of Sapphire Crystal Growth 

Daniel C. Harris*

Naval Air Systems Command, China Lake, California 

ABSTRACT 

Abstract: In Paris around 1890, A. V. L. Verneuil developed a flame fusion 

process to produce ruby and sapphire. By 1900 there was brisk demand for ruby 

manufactured by Verneuil’s method, which was used with little alteration for 50 

years. From 1932-1953, S. K. Popov in the Soviet Union established a capability 

for manufacturing high quality sapphire by the Verneuil process. In the U.S., 

under government contract during World War II, Linde Air Products Co. 

implemented the Verneuil process for making jewel bearings for precision 

instruments. In the 1960s and 1970s, the Czochralski process was implemented 

by Linde and its successor, Union Carbide, to make higher quality crystals for 

ruby lasers. Stimulated by a government contract for structural fibers in 1966, H. 

LaBelle invented edge-defined film-fed growth (EFG). The Saphikon company, 

owned now by Saint-Gobain, evolved from this effort. Stepanov independently 

developed edge-defined film-fed growth in the Soviet Union. In 1967 F. Schmid 

and D. Viechnicki at the Army Materials Research Lab grew sapphire by the heat 

exchanger method (HEM). Schmid later established Crystal Systems, Inc. around 

this technology. Rotem Industries, founded in Israel in 1969, perfected the 

growth of sapphire hemispheres and near-net-shape domes by gradient 

solidification. In the U.S., growth of near-net-shape sapphire domes was 

demonstrated by both the EFG and HEM methods in the 1980s but neither 

method became commercial. Today, domes in the U.S. are made by “scooping” 

sapphire boules with diamond-impregnated cutting tools. Commercial markets 

for sapphire, especially in the semiconductor industry, are healthy and growing at 

the dawn of the 21st century. 

Introduction and Prehistory 

Commercial production of synthetic sapphire is now 100 years old.1

 Sapphire is a readily 

available crystal product used as an optical window for industrial and military applications in 

which the window must withstand extreme environments. Sapphire transmits from the 

ultraviolet through the visible and into the midwave (3-5 μm) infrared regions. It withstands 

high temperature, rapid heating and cooling, high pressure, and resists chemical corrosion. 

Sapphire is the abrasion-resistant window in bar code scanners and the scratch-proof crystal face 

of expensive wristwatches. High crystal perfection, low reactivity, and appropriate unit cell size 

make sapphire an excellent substrate in the semiconductor industry for blue light-emitting diodes 

 

*Daniel.Harris@navy.mil; phone 1-760-939-1649; fax 1-760-939-1617 

Cleared for pubic release; distribution unlimited. 

1 
Report Documentation Page Form Approved

OMB No. 0704-0188

Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and

maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information,

including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington

VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it

does not display a currently valid OMB control number.

1. REPORT DATE

17 MAY 2004

2. REPORT TYPE

N/A

3. DATES COVERED

 - 

4. TITLE AND SUBTITLE

A Century of Sapphire Crystal Growth

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S) 5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Naval Air Systems Command, China Lake, California

8. PERFORMING ORGANIZATION

REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)

11. SPONSOR/MONITOR’S REPORT 

NUMBER(S)

12. DISTRIBUTION/AVAILABILITY STATEMENT

Approved for public release, distribution unlimited

13. SUPPLEMENTARY NOTES

See also ADM201976, 10th DoD Electromagnetic Windows Symposium. Held in Norfolk, Virginia on 18-20

May 2004. , The original document contains color images.

14. ABSTRACT

15. SUBJECT TERMS

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 

ABSTRACT

UU

18. NUMBER

OF PAGES

73

19a. NAME OF

RESPONSIBLE PERSON

a. REPORT

unclassified

b. ABSTRACT

unclassified

c. THIS PAGE

unclassified

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std Z39-18 
and diode lasers. Sapphire is also used for equipment to 

manipulate semiconductor wafers during processing in extreme 

environments. Sapphire and its cousin, ruby, are employed as 

jewel bearings in precision mechanical instruments. 

5 

4

1 2 3

Sapphire is also known as corundum, the natural crystal of 

aluminum oxide, Al2O3 (Figure 1). It is stable up to its melting 

temperature of 2050oC. Its hardness of 9 on the Mohs mineral 

scale is second only to that of diamond. The 3-fold symmetry axis 

of the trigonal crystal, designated c, is also called the optical axis. 

Two-fold symmetry axes designated a and m are found 

perpendicular to the 3-fold axis. Pure corundum is clear and 

colorless. Natural sapphire has a variety of colors. Blue sapphire 

contains iron and titanium impurities whose charge transfer 

transition (Fe2+,Ti4+ → Fe3+,Ti3+) absorbs red light and imparts 

blue color to the crystal.2 The red color of ruby comes from Cr3+

in corundum, which gives rise to electronic transitions that absorb 

visible light. 

Figure 1: Natural 

sapphire (1, 2), natural 

ruby (3), and synthetic 

sapphire (4, 5). 

Early in the 19th century, it was thought that sapphire and ruby were oxides of the elements 

aluminum and silicon.1 In 1817, J. L. Gay-Lussac found that pure aluminum oxide (also called 

alumina) could be prepared by thermal decomposition of ammonium alum, (NH4)Al(SO4)2 •12H2O. 

Alumina prepared by this route remains as the raw material for making sapphire today. In 1840 

H. Rose showed that silicon observed in sapphire was an impurity introduced from the agate 

mortars used to grind sapphire for chemical analysis. Once the true composition of sapphire was 

known, many chemists sought to make the valuable crystal. In the period 1837-1840, H. Gaudin 

used a torch to fuse alumina prepared from ammonium alum to prepare small hexagonal platelets 

of corundum. Mixing alum with chromium salts prior to fusion produced small, strained, hard 

red particles whose density was less than that of natural ruby because of trapped gas. Gaudin 

believed he had made a glass, but modern work suggests that he made crystalline ruby.1 In

1851, H. Senarmont made microscopic rhombohedral crystals by heating solutions of aluminum

chloride to over 350oC in sealed tubes. In 1848, J. J. Ebelman prepared ruby by fusing alumina 

and boric acid with chromium oxide. Ebelman and F. Parmantier prepared crystals from alumina 

dissolved in fused salts at high temperature. Other investigations were carried out by R. 

Boettger, W. Bruhns, A. Brun, H. Debray, H. St.-C. Deville, H. Caron, Daubré, C. Doelter, L. 

Elsner, G. Friedel, H. Grandeau, P. Hautefeuille, M. Houdard, H. Loyer, J. W. Mallet, G. 

Medanich, S. Meunier, H. Moissan, J. Morozewicz, C. F. W. A. Oetling, H. Perrey, L. Schuch, 

and E. Weinschenk.1,3,4

 None of this work produced more than microscopic crystals. 

More successful investigations were led by Edmond Frémy (1814-1894) at the Museum of 

Natural History in Paris.1 Frémy and his assistant, Charles Feil, published a paper in 1877 in 

which they obtained small, clear, red ruby crystals. Fireclay crucibles with 20-kg charges were 

held at red heat for periods up to 20 days. Lead oxide (Pb3O4) was converted to lead aluminate, 

which reacted with silica to give lead silicate plus corundum. Ruby was obtained by adding 2-3 

wt% potassium dichromate to the reaction. After Feil died in 1876, Frémy’s new assistant was 

Auguste V. L. Verneuil (1856-1913), who had applied to work with Frémy at the age of 17. 

Clear 

2 
ruby crystals up to 3 mm in diameter and 

0.3 carat in mass (1 carat = 0.2 grams) were 

grown from alumina in a potassium

hydroxide/barium fluoride flux in a ceramic 

crucible at 1500oC. In unsuccessful 

attempts to increase the size of the ruby 

crystals, flux growth was scaled up at the 

Saint-Gobain glass factory and then in 50-

liter crucibles at the Appert glass factory. 

Although Frémy thought he was 

crystallizing alumina from the flux, Kurt 

Nassau1 suggests that alumina and barium

fluoride give gaseous aluminum fluoride. 

Aluminum fluoride reacts with water vapor 

that diffuses through the porous crucible to 

give alumina, which crystallizes in many 

locations with little chance to grow into 

larger crystals. Frémy summarized his 

investigations in a book in 1891.5 He 

retired in 1892 and died in 1894. Figure 2, 

reproduced from Nassau,6 was taken from

Frémy’s book. Figure 2: Crystal growth storage cabinet from

Frémy’s lab.5,6 

Flame Fusion and the Verneuil Process 

In 1885 rubies selling for $1000-2500 per carat from an unknown source appeared in Geneva 

and were purported to be natural gems.

1 Investigation of the crystals at the Sorbonne in Paris 

and at Tiffany in New York found microscopic gas bubbles suggestive of a high-temperature 

synthetic process. The French Syndicate of Diamonds and Precious Stones ruled that the 

crystals had to be marketed as “artificial,” which reduced their price to $25-40 per carat. 

Modern investigation of “Geneva” rubies by Nassau suggests a 3-stage flame fusion synthetic 

process.1 In the first stage, alumina plus a chromium salt are fused on a ceramic support to form

a tiny crystalline ball. The ball is then turned upside down and growth of a larger crystalline ball 

is continued by adding fresh material to the flame. The final stage appears to require 2 torches to 

enlarge the growing crystal to its final dimensions. The proposed mechanism is supported by 2 

discontinuities in chromium concentration inside “Geneva” rubies. One of the people who 

examined “Geneva” ruby in 1886 was the mineralogist, P. M. E. Jannettaz at the Museum of 

Natural History in Paris. He concluded that fusion was involved in the creation of the “Geneva” 

ruby and he discussed his findings with his colleague, Verneuil. 

While working with Frémy, Verneuil had earned his bachelor, masters, and doctoral degrees. 

When Frémy retired in 1892, Verneuil became professor of applied chemistry at the Museum of 

Natural History in Paris. In 1886, following his introduction to the “Geneva” ruby by Jannettaz, 

Verneuil and G. A. Terreil used a hydrogen-oxygen torch to fuse alumina powder with some

added chromium salt. They obtained tiny particles, which Jannettaz identified as ruby. From

this experiment, Verneuil began in earnest in 1888 to develop flame fusion growth of ruby. 

3 
Working with his student, Marc Paquier, Verneuil developed the flame fusion process well 

enough to write the details in a sealed report which he deposited at the Paris Academy of Science 

in 1891. After further improvement in decreasing growth stress, Verneuil deposited a second 

sealed document at the Academy of Science in 1892. Marc Paquier, presumably the same person 

who assisted Verneuil, displayed ruby crystals at the World Fair in Paris in 1900. The crystals, 

for which there was brisk demand, appear to have been made by the Verneuil process, not the 

Geneva process, and commercial production had already begun by 1900. In 1902, Verneuil 

announced that he had developed a flame fusion process for making ruby and he published full 

details in 1904.7 

Figure 3 is taken from one of Verneuil’s two U.S. patents. To make feed powder, ammonium

aluminum sulfate and ammonium chromium sulfate were each recrystallized 4-5 times and a 

mixture of the two was calcined at 1000-1200oC to give a mixture of the oxides. Ground powder 

was placed in container B in Figure 3 and delivered into tube K by the tapping hammer D. 

Oxygen was also delivered through tube K and illuminating gas was delivered through tube S. 

The flame burned inside the ceramic muffle insulator M whose inside diameter was 25 mm and 

whose inside height was 105 mm. An alumina pedestal L held by a platinum tube could be 

lowered away from the flame by crank P as the crystal grew on the pedestal. A mica window 

covered by a steel shutter, neither of which is shown in Figure 3, enabled the operator to view 

the growing crystal inside the muffle. 

The crystal growth process described in Verneuil’s patent is shown in Figure 4. Powder falling 

through the flame was heated just below its melting point. The initial powder built up a conical 

pile in which the hot particles sintered together to make a rigid “sinter cone.” The upper tip of 

the cone became molten when the cone got sharp enough. Fresh powder landing on the molten 

ball would melt and enlarge the crystal. Only the uppermost skin of the growing crystal was 

molten. As the crystal grew in a vertical direction, the pedestal was lowered to keep the top of 

the crystal at the correct location in the flame. Flame temperature during crystal growth was 

regulated by controlling the flow of oxygen. At the end of a growth run, the flame was shut and, 

if there was not too much strain, the crystal would not shatter. Even so, crystals had so much 

strain that a light tap at the end would split the crystal lengthwise into two halves. A typical 

growth time of 2 hours produced a 15 carat cylinder with a diameter of 6 mm and length of 25 

mm.

In 1909 Verneuil was appointed chief chemist at the Paris laboratory of the New York jewelry 

company, L. Heller and Sons. His charge was to grow blue sapphire for jewelry. The origin of 

the blue color was not known until chemical analyses by Verneuil showed that natural blue 

sapphire always contained both iron and titanium. Armed with this knowledge, Verneuil was 

able to grow deliberately doped blue sapphire. The Paris laboratory was closed in 1911 with the 

successful completion of the project. 

Ruby and sapphire manufacturing by the Verneuil process had begun in Europe prior to 

Verneuil’s publication of 1904.1 One of the largest Verneuil operations was that of Industrie de 

Piérres Scientifiques, Hrand Djévahirdjian in France and Switzerland. The company had a room

with approximately 100 Verneuil torches operating around 1920. Heller Company had planned 

to manufacture blue sapphire in the U.S. but found that labor costs were too high to compete 

with European manufacturing. Blue sapphire was grown for Heller by Baikovsky Brothers in 

4 
France. 

 

Powder 

feed 

Water 

cooling 

jacket

Flame and 

growing 

crystal 

Figure 3: Diagram of Verneuil’s apparatus 

for growing sapphire. From U.S. Patent 

1,004,505, September 26, 1911. 

B. container of feed powder 

D. hammer

G. rotating cam

O. oxygen feed tube 

H. illuminating gas feed tube 

K inner tube carries oxygen 

S. outer tube carries illuminating gas 

M. muffle (insulation) surrounding 

downward-pointing flame 

L. ceramic pedestal 

P. crank for lowering pedestal to keep 

crystal at correct height in flame 

Mechanism to lower 

crystal to keep growth 

surface at correct 

elevation in the flame

 

Figure 4: Method of 

growing sapphire 

described in Verneuil’s 

U.S. Patent 1,004,505. 

Baikovsky had 3 torches in 1903, 80 in 1914, 400 in 1919, and 1600 torches in 1980. By 1980 

there were approximately six large Verneuil manufacturers with a total capacity of 109 carats/yr. 

Most sapphire was cut into jewel bearings for watches and precision instruments. The process of 

cutting jewels wastes approximately 99% of the as-grown boule. 

5 
In the Soviet Union, S. K. Popov (1903-1953) began experiments with the Verneuil method in 

1932.4 By 1938 he had produced a semi-automatic growth apparatus which enabled the 

manufacturing of long thin rods suitable for making jewels for watches and instruments. From

1938 until his death, Popov worked at the Institute of Crystallography of the Academy of 

Sciences of the USSR. In 1945-50 he improved the equipment for making ruby rods, solving 

such problems as accurate supply of powder and uniform heating of the growing crystal. In 

1951-53 he developed a new use for sapphire as a durable fiber guide in the textile industry. He 

also devised equipment for bending corundum rods into shapes. A commentary written by N. N. 

Sheftal’ in 1959 stated that Popov’s equipment was more advanced than that of Western Europe 

and that the crystal quality produced in the Soviet Union was higher than that available 

elsewhere.4 

Birth of the Sapphire Industry in the United States 

Prior to the publication by Verneuil in 1904, industrial production of ruby began in the town of 

Hoquiam, Washington in the period 1903-1904. The story pieced together by Nassau1 states that 

two entrepreneurs, Polson and Ninemire, who had accumulated wealth in the lumber industry, 

hired an assistant of Verneuil to establish a flame fusion facility to grow ruby for jewelry. It was 

necessary to send boules to New York for cutting and the venture as a whole was not 

economical. The arrival of less expensive Verneuil ruby from Europe ended any hope of 

American production. 

There was no further U.S. production of ruby or sapphire until America was cut off from

European supplies of jewel bearings in World War II. The U.S. government issued development 

contracts which led to production by Linde Air Products Co. in Indiana in 1942. One advantage 

that Linde had for sapphire production was that Linde was a major supplier of industrial gases, 

including those used for the Verneuil torch. Linde was later acquired by Union Carbide Corp. 

After the war, the U.S., again, could not compete with Europe for economy in sapphire 

production. In the late 1940s Linde developed a process for making star sapphire and star ruby, 

which contain needles of titanium dioxide, for jewelry. Another market for sapphire was fiber 

guides in the textile industry. The Linde plant in Indiana was closed in 1974 and Union 

Carbide’s Linde Crystal Products Division concentrated on Czochralski crystal growth in 

California and Washington State. In 1999 the Crystal Products Division was acquired by Bicron, 

a division of the French company, Saint-Gobain. In 2000 the division was renamed “SaintGobain Crystals and Detectors”. 

Czochralski Sapphire Crystal Growth 

Verneuil’s flame fusion process, perfected in 1892, hardly changed in the 70 years in which it 

was the only significant production method for sapphire. There is still significant demand for 

Verneuil material at the dawn of the 21st century because the method is the least expensive way 

to make sapphire and ruby whose quality is adequate for many applications. However, higher 

crystal quality demanded by electronic and optical applications, and the need for sizes and 

shapes that cannot be made by flame fusion, sparked the development of other ways to make 

sapphire after 1960. 

6 
The Czochralski crystal growth method was applied to sapphire in the early 1960s.8

 Then other 

growth methods were invented later in the 1960s. Edge-defined film-fed growth was developed 

in the U.S and the related Stepanov method was applied to sapphire in the U.S.S.R. The heat 

exchanger method was developed in the U.S. and gradient solidification was introduced in Israel. 

A resurgence of interest in ruby arose with the invention of 

the ruby laser in 1960 using a Verneuil boule grown by 

Union Carbide in 1959. It was quickly discovered that the 

optical quality of Verneuil boules was not adequate for 

lasers. This dilemma led to the development of sapphire 

growth by the Czochralski method at Union Carbide in the 

1960s. In this process, alumina is melted in an iridium

crucible in an atmosphere of 98% N2 / 2% O2. A seed crystal 

is then dipped into the liquid and withdrawn at a rate of 6-25 

mm/h while rotating at a rate up to 30 rpm. As the seed is 

withdrawn, alumina from the melt crystallizes onto the seed. 

The diameter of the boule could be controlled by the rate of 

withdrawal of the seed. Boule diameters up to 11 cm could 

be obtained from a 15-cm-diameter crucible. Saint-Gobain 

in Washington State and Crystar Research (a division of 

Johnson Matthey) in Vancouver, Canada both produce 

sapphire today by the Czochralski method. 

Iridium 

crucible 

Figure 5: Czochralski 

crystal growth. 

Edge-Defined Film-Fed Growth 

Harold LaBelle, Jr. was a talented technician with only a high school diploma who joined Tyco 

Laboratories in Waltham, Massachusetts in 1962. Previously, he served as a Navy weather 

observer at White Sands Proving Ground and attended New Mexico State University. His early 

experience at Tyco was in the growth of semiconductor crystals by gradient freeze and “traveling 

solvent” methods, from which he gained an understanding of solid-liquid interface control. In 

1965 he began work on an Air Force contract whose goal was to make sapphire fibers for 

reinforcement of metal matrix composites.9,10,11 By analogy with silicon growth at other 

laboratories, LaBelle found that if he plunged a cold tungsten rod into molten alumina, small, 

crystalline alumina dendrites grew from the tungsten, which served as a seed. However, the 

longest dendrites were only 3 mm, which was much shorter than required. In an attempt to 

improve temperature stability, Labelle melted alumina in a tungsten boat in a vacuum

evaporator. When a 0.25 mm tungsten wire was dipped into the melt and carefully lifted out, a 

sapphire crystal grew on the tungsten wire “seed”. This process was essentially a Czochralski 

crystal growth that produced a carrot shaped sapphire crystal with the tapered tip attached to the 

last drop of molten alumina (Figure 6). 

The final diameter of the sapphire depended on the diameter of the liquid drop remaining in 

Figure 6. LaBelle reasoned that a droplet of the right cross section would produce a filament of 

the desired cross section. A method was needed to feed liquid with a constant cross section from

a reservoir so that long filaments could be produced. Therefore, Labelle floated a molybdenum

washer on top of molten alumina and drew a fiber by Czochralski-like growth through the orifice 

of the washer (Figure 7). Several 1-mm-diameter crystals up to 30 cm long were grown in this 

manner. These results were impressive enough to secure additional funding for the project. 

7 
 

Figure 6. Czochralski-like growth of 

sapphire from molten alumina using 

tungsten wire as a “seed crystal”. 

Redrawn from reference 10. 

Figure 7. Sapphire crystal growth by 

the floating orifice technique. Redrawn 

from reference 10. 

For several months, LaBelle grew crystals by this floating orifice technique. Eventually, he 

concluded that floating dense molybdenum on less dense alumina was too delicate for use in 

manufacturing. It then occurred to him that “a molybdenum capillary projecting out of the melt 

might yield the positive result that the floating orifice had, yet represent mechanical, and 

therefore, thermal stability as well.”10 The self-filling tube in Figure 8 provided filaments with 

more regular surfaces and 3-4 times as much strength as from filaments grown earlier.10,12 The

capillary in Figure 9, made from concentric molybdenum tubes, produced the first sapphire 

tubes. Many tubes and ribbons were grown from self-filling tubes in 1967. 

 

Figure 8. Self-filling capillary tube for 

filament growth. Redrawn from

reference 13. 

Figure 9. Self-filling capillary 

tube for tube growth. Redrawn 

from reference 10. 

8 
In a key observation, LaBelle noticed that sometimes the sapphire diameter grew larger than that 

of the orifice from which it was drawn. The difference depended on the angle of the upper 

surface of the orifice. If the top surface of the molybdenum were flat, the liquid would spread to 

the edge and then stop. A crystal grown from such a capillary would be just as wide as the outer 

diameter of the molybdenum. LaBelle and his assistant, John Bailey, built the die in Figure 10, 

which easily produced a tube whose outer diameter was equal to the outer diameter of the 

molybdenum. Because the dimensions of the sapphire tube grown in Figure 10 were controlled 

by the molybdenum die, Labelle’s supervisor, Ed Mlavsky coined the term “edge-defined filmfed growth,” or “EFG.” 

 

Figure 10. First edge-defined film-fed growth 

of a sapphire tube whose wall dimensions were 

equal to the dimensions of the molybdenum die. 

Redrawn from reference 10. 

Figure 11. Die used to prove that the 

edges of the molybdenum die defined 

the edges of the sapphire crystal. 

Redrawn from reference 10. 

To distinguish between edge-defined film-fed growth and self-filling tube growth, the die in 

Figure 11 was constructed. If the top surface of the molybdenum die controlled the shape of the 

crystal, then a uniform tube would grow from the molten alumina fed through the four capillary 

openings. Sure enough, the die produced a tube with uniform walls. “The uniqueness of EFG in 

shaping was therefore established ... since the capillaries were of totally different cross-sectional 

shape than the growing crystal.”10 LaBelle suggested calling the new process “continuous 

shaped film propagation,” but Mlavsky’s “edge-defined film-fed growth” prevailed. 

The purpose of the Air Force contract at Tyco Laboratories was to grow long filaments of 

sapphire. To accomplish this, LaBelle had to invent clever mechanisms to guide the growing 

fiber and to pull long lengths with a small machine. Fibers grown in the Air Force program in 

1965-66 were nearly opaque and there was no immediate demand for the product. However, in 

the 1970s, transparent material could be grown in many shapes.11,12,13 An application with a 

significant market was 12.5 × 12.5 × 0.6 mm windows for erasable programmable read-only 

memory chips. EFG growth of transparent sapphire optical fibers for high temperature 

environments was stimulated in the 1980s by funding from the Department of Energy. 

9 
Concurrent with the work of LaBelle in the 

1960s, Stepanov independently applied his 

shaped growth method to sapphire in the Soviet 

Union.14,15 His method was originally used in 

the late 1930s to grow shaped metal crystals.16 

The Stepanov method uses wettable or 

nonwettable aids to shape the melt column

which, in turn, dictates the shape of the grown 

crystal (Figure 12).13 By contrast, in edgedefined film-fed growth, the shape of the die, not 

the shape of the melt column, controls the shape 

of the crystal. 

In 1970 Tyco created the Saphikon Division to 

produce EFG sapphire in Waltham. In 1978 the 

Saphikon Division moved to Milford, New 

Hampshire. In the 1970s and 1980s Saphikon 

received the bulk of its revenue by licensing the 

EFG process to companies such as Kyocera, 

RCA, Corning, and Allied Signal, all of whom

saw commercial potential for sapphire substrates 

for the newly developing silicon-on-sapphire 

electronics technology. In 1982, Joseph 

Gaziano, the president of Tyco, died. The new 

president, John Fort, sought to sell the Saphikon 

Division, which had less than two million dollars 

per year in revenue. Eventually he made a deal with LaBelle that was “too good to refuse”. 

LaBelle purchased Saphikon in 1985 and resold it at a profit in 1987. Saphikon remained 

independent until 2000 when Saint-Gobain purchased the company and the rights to make 

sheets, rods, tubes, and 3-dimensional shapes. The newly formed, independent company Photran 

retained exclusive rights to manufacture sapphire fibers. 

Figure 12. Wettable shaping aid used in 

Stepanov growth. The dimensions of the 

crystal are determined by the dimensions of 

the liquid feed column. Redrawn from

reference 13. 

Kyocera in Japan acquired EFG technology from Saphikon and further developed the process. 

Kyocera sells r-, a-, or c-plane sheets up to 20 cm wide x 30 cm long x 0.02-2 cm thick. 

Kyocera also sells c-axis rods and tubes. 

Heat Exchanger Method 

The Heat Exchanger Method (HEM) for growing large sapphire boules was invented by Fred 

Schmid and Dennis Viechnicki at the Army Materials Research Lab in Watertown, 

Massachusetts in 1967.17,18 Fresh out of college in the early 1960s, Schmid worked in 

manufacturing at the Watertown Arsenal, where he gained experience in the directional 

solidification of metals and with a helium-cooled arc furnace for casting titanium. He then went 

to Northeastern University to earn a masters degree in materials science. Returning to the 

Watertown Lab in 1967, Schmid set to work with Viechnicki on directional solidification of an 

alumina melt onto a sapphire seed crystal. 

10 
The modern implementation of Schmid and Viechnicki’s heat-exchanger method at Crystal 

Systems in Salem, Massachusetts is shown in Figure 13. A sapphire seed crystal is placed at the 

bottom of a molybdenum crucible which is then loaded with pure alumina crackle, a byproduct 

of the Verneuil process. The furnace is evacuated and resistively heated to melt the crackle 

while keeping the seed just below its melting point by passing helium gas through the heat 

exchanger beneath the center of the crucible. Heat and vacuum help purify the alumina by 

vaporizing some impurities. After partial melting of the seed, helium flow is increased to cool 

the seed and initiate crystallization of alumina onto the seed. The furnace is held at constant 

temperature during growth of the crystal, which proceeds out from the seed in 3 dimensions. 

After crystallization is complete, the furnace temperature and the helium flow are decreased and 

the boule is slowly annealing in situ. The long slow cooldown produces sapphire of the highest 

crystal quality. Boules with a diameter of 34 cm and a mass of 65 kg are routinely produced and 

boules up to 38 cm have been grown. 

Single crystals of sapphire were grown in an 18-mm-diameter crucible in 1967 at Watertown. 

By 1969, after about 50 attempts, crack-free sapphire with a diameter of 76 mm was grown. By 

1971 the diameter was up to 152 mm. The first patent for the process, which was then known as 

the Schmid-Viechnicki technique, was issued in 1969. 

 

(a) (b)

(c)

Figure 13: (a) Furnace used at Crystal Systems to grow sapphire by the Heat Exchanger 

Method. (b) The first sapphire boule grown at Watertown in 1967. (c) Production-quality 34-

cm-diameter sapphire boule. Courtesy Crystal Systems, Inc. 

11 
By early 1971, Schmid was convinced that the new method was a breakthrough and wanted to 

find a commercial market for the product. He found interest at Inselec and Insaco in obtaining 

sapphire wafers for silicon-on-sapphire electronics. Schmid persuaded a sailing buddy and an 

accountant to invest in creating the company, Crystal Systems, of which Schmid would own 

51%. The company was incorporated in August 1971 after Schmid had purchased a scrapped 

furnace from Raytheon in July. He began refurbishing the furnace in his garage and soon moved 

the operation to Shetland Industrial Park in Salem. For the first year of the company, Schmid 

held his old job at Watertown and worked on the furnace at night. By July 1972 he grew his first 

152-mm-diameter boule, from which 51-mm cores were drilled for silicon-on-sapphire substrate 

wafers. In. September 1972 Schmid resigned from Watertown to devote full attention to Crystal 

Systems. He hired his first helper (who was “just getting out of high school”) and his wife 

handled advertising. First-year sales were less than fifty thousand dollars. Shortly after the first 

advertising went out in 1974, Schmid received a letter from Union Carbide indicating that 

Crystal Systems was infringing on their patent and offering to license Union Carbide technology. 

This claim led Schmid to clarify the difference between the processes and to obtain a patent for 

his technique, whose name he changed to “heat-exchanger method” because of its unique, 

controllable heat exchanger. 

In the mid 1970s Crystal Systems began to hire full-time employees. Schmid developed a fixedabrasive slicing technique using a diamond-impregnated blade or wire to slice wafers from a 

cylinder with minimal loss of material. The National Aeronautics and Space Administration 

selected HEM sapphire for use in satellites because of its extremely low optical scatter. In 1978 

the company moved to its current, larger quarters in the same industrial park. In 1979 Crystal 

Systems received a contract to grow laser-quality ruby in one of the first actions of the 

government’s new Small Business Innovative Research program. In 1987-89, titanium-doped 

sapphire for lasers was commercialized. Military and commercial markets for sapphire 

expanded greatly in the 1980s. In 1974 Crystal Systems got its first government contract to 

grow silicon and in 1977 Chandra Khattak at Crystal Systems used the heat-exchanger method to 

grow crack-free polycrystalline silicon ingots in high purity silica crucibles for the first time. 

HEM silicon for photovoltaics and equipment for growing silicon are currently major products 

of Crystal Systems, in addition to sapphire and crystal slicing equipment. HEM silicon ingots 

weighing 240 kg with a cross section of 69 × 69 cm are routinely produced. 

Sapphire Domes 

One of the most demanding applications for an infrared window material is the seeker dome on 

an infrared-guided missile. The dome must withstand stress from very rapid heating and it must 

survive collisions with raindrops, sand particles, and insects in the air. Among the infraredtransparent materials available in the 1980s, sapphire was clearly the most durable with respect 

to thermal stress and particle impact. However, the cost of growing sapphire was high and the 

cost of fabricating it into an optically polished hemisphere was even higher. To decrease the 

cost, the government invested in two efforts to grow near-net-shape domes which would require 

relatively little machining after growth. 

12 
One Navy-funded effort at Saphikon led to a 

Manufacturing Technology contract in 1989-

92. A curved sapphire seed crystal was 

placed in contact with a curved slit at the top 

of a molybdenum die for EFG growth. The 

seed was slowly withdrawn in a path that 

traced an arc in space. The result was an asgrown dome, such as that in Figure 14, which 

could be ground and polished into a finished 

dome. However, the crystal quality was not 

as high as desired and the manufacturing 

process was never optimized.19,20 Figure 14: As-grown EFG sapphire 

produced by Saphikon.19,20

Another Navy Small Business Innovative Research contract was conducted at Crystal Systems. 

Work done in the mid to late 1980s used the apparatus shown at the left in Figure 15 to grow the 

near-net-shape domes at the right.21,22,23 Two hemispheric molybdenum mandrels were inserted 

into the crucible in which sapphire was grown. After a boule was grown and cracked apart, 

sapphire that crystallized in the volume between the two mandrels had a hemispheric shape. 

This method suffered from cracks extending into the boule and it was never taken beyond an 

initial demonstration. 

 

Figure 15: Molybdenum apparatus at left was used at Crystal Systems to grow near-net-shape 

sapphire domes at right.21-23 Photos courtesy Crystal Systems.

Domes were formerly produced from sapphire boules by machining each dome out of a 

cylindrical piece of material, as shown at the left in Figure 16. This process wastes valuable 

material and requires a great deal of machining. A cost effective method for making domes—the 

process used today in the U.S.—is called scooping. Shown at the middle of Figure 16, 7 nested 

domes could be taken from the same volume of material that produced 3 domes by conventional 

machining. Diamond-impregnated cutting tools shown at the right of Figure 16 are used to cut 

out first the inner surface and then the outer surface of consecutive domes. In the cutting 

process, the sapphire is rotated in one direction while the tool is rotated against it in the opposite 

13 
direction. At the end of the scooping, neighboring domes are connected by a small cylinder of 

material at the apex. The domes are broken apart by tapping and then they are ground and 

polished to their final finish. 

 

Figure 16: Line drawings compare conventional use of a boule to make 3 domes and scooping to 

make 7 domes from the same volume. Photograph shows diamond-impregnated scooping tools 

used at Crystal Systems for scooping sapphire. Photo courtesy Crystal Systems. 

Rotem Industries, which was founded in 1969, provides sapphire products for defense 

applications. The gradient solidification method for sapphire growth was developed at Rotem to 

produce high quality, near-net-shape domes.24,25,26,27,28 In Figure 17, alumina is loaded into a 

hemispheric molybdenum crucible containing a sapphire seed at the bottom. The crucible is 

heated in vacuum to produce a gradient of temperature, with the highest temperature at the top. 

When the seed has partially melted, the temperature is lowered in a carefully controlled manner 

so that crystallization proceeds out from the seed crystal. An as-grown hemispheric dome and a 

solid hemisphere are shown in Figure 18. 

Seed 

Vacuum

system 

Power

control

3-phase graphite 

heating element 

Mo crucible

Sapphire

Crucible lid

Mo radiation shield

Pyrometer

Figure 17: Apparatus for 

growing sapphire by 

gradient solidification at 

Rotem Industries in Israel. 

14 
In the heat-exchanger method, highest crystal quality is produced when growth takes place along 

the a-axis of the crystal. For the boule in Figure 13(c), the a-axis is the cylindrical axis. The 

optical axis of sapphire (the c-axis) is perpendicular to a and comes out the curved side of the 

boule. To make c-axis domes, a cylindrical core is drilled from the side of the boule and domes 

are scooped out from the core. In Rotem’s gradient solidification method, the thermal mass is 

low enough to permit the growth of good quality c-axis boules and domes, as well as a-axis 

material.

c-axis or a

As-grown boule Polished As-grown dome 

Figure 18: Sapphire produced at Rotem Industries by 

gradient solidification. When a c-axis flat or dome is 

viewed through crossed polarizers, as shown at the left, 

crystal imperfections and grain boundaries appear as 

irregularities in the circular fringes and characteristic 

cross. The symmetry of the pattern in the photo at the 

left is evidence of high crystal quality. Each line of the 

black cross, referred to in optics as an isogyre, is 

parallel or perpendicular to the direction of a polarizer, 

and occurs from extinction of either p- or s-polarized 

light when only light of that polarization is incident on 

the crystal. Photos courtesy Atara Horowitz. 

 

Dome viewed through crossed polarizers 

Outlook 

Current issues for sapphire production for windows and domes include: (1) The cost of sapphire 

is high. Much of the cost is in machining and polishing. (2) There is a need for larger area 

windows. The EFG method can make inherently large windows. The Heat Exchanger method 

has been scaled up to 38-cm-diameter, but larger sizes would be desirable. Materials Systems, 

Inc. has demonstrated a way to bond sapphire panes to each other to make large windows, but 

the bond lines are not as strong as sapphire and they provide an optical discontinuity.29 (3) 

Optical fabrication is not well enough controlled to give reproducible mechanical properties. It 

is virtually impossible to know the mechanical strength of a particular sapphire part unless it is 

proof tested. In the absence of proof testing, designs must be conservative to be reliable. 

15 
Acknowledgements 

A great deal of sapphire history is presented in the wonderful book, Gems Made by Man by Kurt 

Nassau. I am indebted to the following people who shared their knowledge with me: Fred 

Schmid and Chandra Khattak of Crystal Systems; Herb Bates, Cy Gregg and Tim Davis, 

formerly of Saphikon; Larry Rothrock of Photran and Union Carbide; and Atara Horowitz of 

Rotem. 

References 

1. K. Nassau, Gems Made by Man, Chilton Book Company, Radnor, PA, 1980. 

2. K. Nassau, Gemstone Enhancement, 2nd ed, Butterworth-Heinemann, Oxford, 1994, p. 38; 

G. Lehmann and H. Harder, “Optical Spectra of Di- and Trivalent Iron in Corundum,” Amer. 

Min. 55, 98-105 (1970). 

3. P. Chirvinskii, Artificial Production of Minerals in the Nineteenth Century [in Russian], 

Kiev, 1903-1906. 

4. S. K. Popov, “Growing Synthetic Corundum as Rods and Boules” in Growth of Crystals, 

Vol. 2 (A. V. Shubnikov and N. N. Sheftal’, Eds.), English translation by Consultants 

Bureau, New York, 1959, pp 103-135. 

5. E. Frémy, Synthèse du Rubis, Libraire des Corps Nationaux, Paris, 1891. 

6. K. Nassau, “Dr. A. V. L. Verneuil: The Man and the Method,” J. Cryst. Growth 13/14, 12-

18 (1972). A more detailed biography appears in K. Nassau and J. Nassau, “Dr. A. V. L. 

Verneuil and the Synthesis of Ruby and Sapphire,” Lapidary J., 24, 1284-96, 1442-47, 1524-

32 (1971). 

7. A. Verneuil, “Memoire sur la Reproduction du Rubis par Fusion,” Ann. Chim. Phys. Ser 8, 3: 

20-48 (1904). 

8. T. B. Reed and R. E. Fahey, “Resistance Heated Crystal l Puller for Operation at 2000oC,” 

Rev. Sci. Instr. 37, 59 (1966). 

9. Final report for Air Force contract AFML-TR-66-246 (1966). 

10. H. E. LaBelle, “Experimental Work Leading to EFG,” Am. Assoc. Crystal Growth 

Newsletter, July 1984. 

11. H. E. LaBelle, J. Serafino, and J. J. Fitzgibbon, “Recent Developments in Growth of Shaped 

Sapphire Crystals,” Proc. SPIE 683, 36-40 (1986). 

12. B. Chalmers, H. E. LaBelle, Jr., and A. I. Mlavsky, “Edge-Defined, Film-Fed Crystal 

Growth,” J. Cryst. Growth 13/14, 84-87 (1972). 

13. H. E. LaBelle, Jr., “EFG, The Invention and Application to Sapphire Growth,” J. Cryst. 

Growth 50, 8-17 (1980). 

14. P. I. Antonov, S. P. Nikanorov, and V. A. Tatarchenko, “The Growth of Controlled Profile 

Crystals by Stepanov’s Method,” J. Cryst. Growth 42, 447-452 (1977). 

15. P. I. Antonov, “Shape and Properties of Crystals Grown from the Melt by the Stepanov 

Techniques” in Growth of Crystals, Vol. 13 (E. I. Givargizov, Ed.), English translation by 

Consultants Bureau, Plenum, New York, 1986, p 198; V. A. Borodin, T. A. Steriopolo, and 

V. A. Tatarchenko, “Growing Profiled Sapphire Crystals by Variational Shaping” in Growth 

of Crystals, Vol. 15 (E. I. Givargizov and S. A. Grinberg, Eds.), English translation by 

Consultants Bureau, Plenum, New York, 1988, p 183. 

16. A. V. Stepanov, “Method of Producing Articles (Sheets, Tubes, Rods, Various Sections, etc.) 

Directly from Liquid Metal. I.,” Soviet Phys. Tech. Phys. 4, 339 (1959). 

16 
17. F. Schmid and D. Viechnicki, “Growth of Sapphire Disks from the Melt by a Gradient 

Furnace Technique,” J. Am. Ceram. Soc. 53, 528 (1970). 

18. F. Schmid, A Dream That Came True: Reminiscences of Fred Schmid on the Occasion of 

Crystal Systems 25th Aniversary, Crystal Systems, Salem, Massachusetts, 1997. 

19 J. W. Locher, H. E. Bates, W. C. Severn, B. G. Pazol, and A. C. DeFranzo, “80 mm EFG 

Sapphire Dome Blanks Yield High Quality, Low Cost Single Crystal Domes,” Proc. SPIE

1760, 48-54 (1992). 

20. J. W. Locher, H. E. Bennett, P. C. Archibald, and C. T. Newmyer, “Large Diameter Sapphire 

Dome: Fabrication and Characterization,” Proc. SPIE 1326, 2-10 (1990). 

21. C. P. Khattak and F. Schmid, “Production of Near-Net-Shaped Sapphire Domes Using the 

Heat Exchanger Method (HEM),” Proc. SPIE 1760, 41-47 (1992). 

22. F. Schmid and C. P. Khattak, “Current Status of Sapphire Technology for Window and 

Dome Applications,” Proc. SPIE 1112, 25-30 (1989). 

23. C. P. Khattak, A. N. Scoville, and F. Schmid, “Recent Developments in Sapphire Growth by 

Heat Exchanger Method (HEM),” Proc. SPIE 683, 32-40 (1986). 

24. A. Horowitz, S. Biderman, G. Ben Amar, U. Laor, M. Weiss and A. Stern, “The Growth of 

Single Crystals of Optical Materials By the Gradient Solidification Method”, J. Cryst. 

Growth 85, 215-222 (1987). 

25. S. Biderman, G. Ben Amar, Y. Einav, A. Horowitz, U. Laor, M. Weiss and A. Stern, “Crystal 

Growth of Optical Materials by the Gradient Solidification Method”, Proc. SPIE 819, 157 

(1987). 

26. S. Biderman, A. Horowitz, Y. Einav, G. Ben Amar, D. Gazit, A. Stern and M. Weiss, 

“Production of Sapphire Domes by the Growth of Near-Net-Shape Single Crystals”, Proc. 

SPIE 1535, 27-34 (1991). 

27. A. Horowitz, S. Biderman, D. Gazit, Y. Einav, G. Ben Amar and M. Weiss, “The Growth of 

Dome Shaped Sapphire Crystals by the GSM Method” J. Cryst. Growth 128, 824-828 

(1993). 

28. A. Horowitz, S. Biderman, Y. Einav, G. Ben Amar, and D. Gazit, “Improved Control of 

Sapphire Crystal Growth”, J. Cryst. Growth 167, 183 (1996). 

29. R. Gentilman, P. McGuire, D. Fiore, K. Ostreicher, and J. Askinazi, “Large Area Sapphire 

Windows,” Proc. SPIE 5078, 54-60 (2003); P. McGuire, B. Pazol, R. Gentilman, J. 

Askinazi, and J. Locher, “Large Area Edge-Bonded Flat and Curved Sapphire Windows,” 

Proc. SPIE 4375, 12-19 (2001). 

17 
A Century o

Sapphire

Crystal Grow

10th DoD Electromagnetic Windows Symposium

Dan Harris

Naval Air Systems Comm

China Lake, Californ

Daniel.Harris@navy.m

May 2004

Soviet

Verneuil

Ruby

Circa 1950

Home 
Ruby red color comes from percent Cr3+ substituted for 

Blue sapphire color comes from a combination of Fe2+ + Ti4+ im

Fe2+ + Ti4+Fe3+ + Ti3+

Charge-transfer

λmax

≈ 600 nm

absorption band

Pure Al

2

O

3 is colorles

Sapphire, also called corundum, is Al

2

O
Sapphire CrystalMelting point = 2050

°

C

Mohs hardness = 9
•1800: Ruby and sapphire were thought to consist 

of Al2O3 and SiO2

•1817: Gay-Lussac:•1840: Rose: Found SiO2 in sapphire is from 

agate mortar used for grinding

•1837-72: Gaudin: Fused alum + Cr salt with torch → hard red partic

•1800s: Other corundum reports: Senarmont, Ebelman, Moissan, Parmantier, 

Brun, Debray, Deville, Caron, Daubré, Doelter, Elsner, Friedel, Grandeau, Hau

Loyer, Mallet, Medanich, Meunier, Morozewicz, Oetling, Perrey, Schuch and W

•1877: Edmund Frémy (1814-1894), Museum of Natural History, Pa

History of artificial ruby and sapphire:

Kurt Nassau, “Gems Made by Man” (Chilton Boo

Lead oxide → lead aluminate

Lead aluminate + silica → lead silicate + thin, fragile cor

Addition of 2% K2Cr2O7 to reaction → ruby crystals 

Ammonium alum

Heat (NH4)Al(SO4)2•12H2O pure Al2O3

Joseph L

17
Auguste V. L. Verneuil, age 19

(1856-1913)

At age 17, Verneuil applied to work 

at the Museum of Natural History, Pwas hired to work on flux growth of Verneuil earned bachelors, masterswhile working for Frémy.

1892-1905: Professor of Applied CMuseum of Natural History. Interes

•chemistry of selenium•phosphorescence of zinc blende•rare earth elements•purification of glycerin•high-refractive-index glass for te•growth of ruby and sapphire

Nassau, Gems Made by ManSee also K. Nassau, J. Crystal Growth 1972, 13/14, 12
Crystals up to 1/3 carat

(1 carat = 200 mg)

Crystallization of Al2O3 + K2Cr2O7 f

KOH and BaF2 at 1500°C in porous 

crucible 

3BaF2 + Al2O3 → 2AlF3(g) + 3B

2AlF3(g) + 3H2O → Al2O3 + 6HF 2HF + BaO → 3BaF2 + H2O 

In attempts to increase crystal sizetransferred to large ovens of Saint-Appert glass factories with 50-L cruVapor phase nucleation in reaction many small cavities and prevents gcrystals1891: Frémy publishes book summ

growth of rubyFrémy retired in 1892 and died in 1

1876-1892: Frémy and Verneuil - Flux Growth o

10 mm

Nassau, Gems Made by Man
Flux-grown ruby

Frémy and Verneuil

Flux Growth

Jewelry with synthetic ruby Frémy’s storage cabin

Nassau, Gems Made by Man
Geneva Ruby

• 1885: Rubies of quality worth $1000-$2500/carat appeared on marke• 1886: Prof. F. Friedel of Sorbonne observed gas bubbles in Geneva 

concluded that stone was made by high-temperature fusion pro

• 1886: French Syndicate of Diamonds and Precious Stones rules Gen

man-made and must be sold as “artificial” ⇒ price drops to $

• 1886: G. F. Kunz of Tiffany examined Geneva ruby and concluded (p

incorrectly) that it was made by Frémy/Verneuil flux growth pro

• 1904: Geneva ruby production ceases when Verneuil published his p

Nassau, Gems Made by Man
Geneva Ruby Growth Process as Reconstructed by K

A. Tiny boule grown at tip of sinter cone

from pure Al

2

O

3 powder + Cr salt

B. Break off and turn boule overC. Further growthD. Complete growth with 2 torches and

rotation of boule support

Discontinuities in of Geneva ruby cto different stageprocess

Cr (wt %)

Millim

Nassau, Gems Made by Man
• 1886: Mineralogist P. M. E. Jannettaz at Museum of Natural 

History, Paris, examined Geneva ruby and concluded that fusion was involved in its fabrication. Jannettazdiscussed his observations with Verneuil.

• 1886: Verneuil and G. A. Terreil fused alumina powder plus Cr salt to 

microscopic single-crystal ruby, as confirmed by Jannettaz.

• 1888: Verneuil begins to investigate solidification of molten Al2O3 as a

flux growth. The only practical way to obtain 2050°C needed to 

was H2-O2 torch or gas-O2 blow torch.

• 1891: Working with his student, M. Pacquier, Verneuil had developed 

we now call Verneuil flame-fusion crystal growth. Verneuil depthe process in a sealed document at the Paris Academy of Sciecracking was main unsolved problem.

Origins of Flame Fusion (Verneuil) Crystal Gro

Nassau, Gems Made by Man
• 1892: Verneuil eliminated crystal cracking by making contact area be

crystal and sinter cone as small as possible. A second sealed details was deposited at Paris Academy of Science.

• 1900: Pacquier exhibits ruby crystals at Paris World’s Fair. Source o

unknown, but it was reported that the Paris manufacturer made new Verneuil process (not the Geneva process) and “was able 

production to France and Germany.”

• 1902: Verneuil announces details of flame fusion process• 1904: Full publication: A. Verneuil, “Memoire sur la reproduction du r

fusion,” Annales de Chimie et de Physique Ser. 8, 3: 20-48 (19

Sintercone

Initial fused region wheretiny crystal begins to grow

Nassau, Gems Made by Man

Initi

Verne

in Mu

and S
Verneuil’s Flame Fusion Apparatus

Muffle furnacecrystal growthzone

Nassau, Gems Made by Man

Powderfeed

Torch pointing

down

Mechanism tolower crystalduring growth
B. Container filled with feed pow

screen on lower end 

(NH

4)Al(SO

4)2

•12H

2

O

+

(NH

4)Cr(SO

4)2

•12H

2

O

1200

°

Recrystallized 4-5

× 

D. Tapping hammerG. Rotating camO. Oxygen inletK. Inner tube carries powder pluH. Fuel (illuminating gas) inletS. Outer tube carries fuelM. Downward pointing flameL. Alumina ceramic pedestal heP. Crank lowers pedestal during 

Nassau, Gems Made by Man

Verneuil Apparatu

US Patent 1,004,505 

– Septembe

Flameandfurnace

Powderfeed

Watercoolingjacket

Micawindow

Mechanism forlowering thegrowing crystal

Flame
Sintercone

Initial fused region wheretiny crystal begins to grow

1. Hot, almost melted powder 

falls on alumina pedestal and builds up sintered cone

2. Uppermost tip of cone 

melts

3. Molten drop enlarges

Verneuil Flame Fusion Process

Nassau, Gems Made by Man

Verneuil-grown ruby in Museum of Arts and Sciences, Paris

1 2 3 4 5

4. Molten drop enlarges5. Pedestal is lowered to 

maintain molten region constant height

6. Flame shutoff time is 

critical to avoid crackin
Cut Verneuil ruby

Curved growth striation

almost all Verneuil cr

Early Verneuil boule grown

on natural ruby seed crystal

Nassau, Gems Made by Man

Typical ruby boule: taper~25 mm long and 6 mm dweighing 15 caratsAfter growth, ruby boule iit splits in half lengthwise
First U.S. Synthetic 

Hoquiam Ru

Nassau, Gems Made by Man

• 1903-1904: Lumber businessmen Polson and Ninemire set up factory 

manufacture ruby in Hoquiam, Washington. 

•Kurt Nassau argues that technology was probably provided by one of 

French assistants.

•Surviving Hoaquiam rubies are low quality material made by Verneuil 

Rubies are small, strained, and have many gas bubbles

• Rubies had to be sent to New York for cutting•Within a few years, cheaper, higher quality Verneuil ruby from Europe 

Hoquiam venture.
Auguste V. L. Verneuil

Age 55 in 1911

• 1905: Verneuil becomes Profes

“lime, cement, ceramics, glassmaking” at NationaConservatory of the Arts Sciences, Paris

• 1909: Verneuil becomes chief c

Paris laboratory of L. Heof New York (later HellerSets up factory to producblue sapphireBy analyzing natural, bluVerneuil discovered that color is associated with Fimpurities

Nassau, Gems Made by Man
Heller Laboratory in Pa

with Verneuil torc

Prof. Verneuil

Nassau, Gems Made by Man

By 1907, several manwere producing synthea total rate of 5 million 
Verneuil growth room with almost 100 torches in 

Industrie de Pi

érres Scientifiques, Hrand Dj

évahirdjian, Switze

Nassau, Gems Made by Man
Verneuil Growth Room of Dj

évahirdjian

Plant with 270 Torches (~1970s)

Nassau, Gems Made by Man
Savva K. Popov: Soviet Pioneer in Ruby and Sapph

S. K. Popov (1903-1953)

1932: Began work on Verneuil c1938: Produced semi-automatic 

apparatus to make long thsuitable for watch jewels

1945-50: Improved device for makin1951-53: Developed new use for co

• fiber guide for making art• flame polishing of corund• method of bending corun

Institute of Crystallography, Academy of Sciences of USS

S. K. Popov in Growth of Crystals (A. V. Shubnikov and N. N. Sheftal’, eds), Chapman & Hall, London, 1959, p

1959 assessment by N. N. She

Popov made more uniform crystoptimizing feed and heating conEquipment and crystal quality bethan those in Western Europe
1939 1950

50 mm

Ruby boules circa 1

S. K. Popov in Growth of Crystals (A. V. Shubnikov and N. N. Sheftal’, eds), Chapman & Hall, London, 1959, pp 104-135

Popov’s work
Nassau, Gems Made by Man 

Linde history here

Linde Air Products Co. Verneuil Ruby and Sapphir

• No synthetic ruby/sapphire production in U.S. after Hoquiam•With European sources of jewel bearings cut off in World War II, 

government issued development contracts

• Linde Air Products Co. begins Verneuil production in East Chicag

Linde was a compressed gas producer

•After World War II, Linde could not compete with lower European 

costs. Linde developed automated process for making 81 cm x 5 that could be efficiently cut into jewel bearings

Linde Verneuil growth in 1960
Nassau, Gems Made by Man 

• Partial melting of feed powder occurs in flame, with complete meltin

layer on top of boule. 30-40% of feed powder is lost and cannot be 

• Boule is lowered at 1 cm per hour• Flame is shut suddenly at end of run. “If the boule does not shatte

ten seconds, then the remaining stress will be relieved by a light tap hammer, which causes the boule to split in half.”

Verneuil Crystal Growth in 1979

Corundum different chas differe
Nassau, Gems Made by Man 

1960: Demand for Ruby Crystals for Lasers Sp

Development of Larger Verneuil Boules an

Eventually Led to Czochralski Crystal Grow

43-cm-long Linde Verneuilruby weighing 4500 carats

19-cm-long early Czochralski ruby from Linde

120-carat rubyfrom Linde

1974: Linde East Chicago facility closes and U.S. ruby growth ceases

Linde Crystal Products Dbecomes part of Union Cafocuses on Czochralski g
Nassau, Gems Made by Man 

Czochralski Crystal Growth of Corundum

• In 1979, Verneuil ruby and sapphire was least expensive variety an

for gems, watch and instrument bearings, thread guides in weaving balls in ball-point pens, and phonograph needles (remember those?

• Higher crystal quality was needed for lasers• Czochralski crystal growth

• Pure Al2O3 is melted in iridium

crucible just above 2050°C

• Sapphire seed crystal is dipped

into melt. If temperature is too low,melt crystallizes. If temperature istoo high, seed melts.

• Seed is rotated (up to 30 rpm) and

pulled out of melt at 6-25 mm/h

• Atmosphere is typically 98%N2-2%O2

• Careful control of pull rate required 

for constant diameter boule

• 11-cm-diameter crystals can be 

pulled from 15-cm crucible
Nassau, Gems Made by Man 

Union Carbide Czochralski Crystals

4.2 kg ruby

10 kg sapphire

Czochralski sapphire appInfrared and ultraviolet winWindows for xenon lampsSodium lamp tubesHigh-pressure cell opticsPhotomultiplier tube face Ultracentrifuge cell windowCorrosion-resistant cells, High-power laser opticsSemiconductor wafer carrPhotomasks and platesRadiation light pipesTransparent electronic suOptical flatsMicrowave output windowHigh-temperature process 

---From Union Carbide 
Union Carbide Sapphire Plant i

Washougal, Washington, 1988

1999: Union Carbide Crystal Products Division acquired by 

Bicron was the successor to Harshaw Chemical Co, a producer of optical crystals. Bicron had been acquireSaint-Gobain in 1990.

2000: Sapphire division renamed 

“Saint-Gobain Crystals an

Detectors

”

2003: Czochralski sapphire is still produced at Washougal p
Nassau, Gems Madeby Man

• Melt Al2O3 in molybdenum crucible

• Melt wets surface of molybdenum die and moves 

up by capillary attraction

• Dip sapphire seed crystal into melt on top of die• Pull seed crystal to draw out crystallizing Al2O3

EFG-draw

(Tyco 

EFG Growth Method: Edge-Defined Film-Fed G

• Research at Tyco Laboratories, Waltham, MA, funded by Air Force i

develop EFG continuous sapphire filament for reinforcement of metacomposite (Report AFML-TR-66-246,1966)

• EFG method invented at Tyco by Harold E. LaBelle, a technician wit

education. Patent issued to LaBelle in 1971
Sapcrysfilam

1. Czochralski-like growth of 

sapphire from molten alumina using tungsten wire as a “seed crystal”. Diameter of crystal is related to diameter of remaining liquid drop

Genesis of EFG Crystal Growth

2. Floating orifice: Mo washer flo

alumina. Diameter of crystal fgoverned by diameter of orificenot stable enough for manufac
3. Self-filling capillary tube for 

sapphire filament growth. Mo no longer floats on melt

Genesis of EFG Crystal Growth

4. Self-filling capillary fo

of sapphire tube
5. First Edge-Defined Film-Fed Growth 

of sapphire filament. Diameter of die, not diameter of melt column, dictates diameter of filament

Genesis of EFG Crystal Growth

6. Experiment proved th

of the Mo die defined the sapphire crystal.

Moltenalumina

• LaBelle suggested the name “continuous shaped film 

propagation”

• His boss, Ed Mlavsky, called it “edge-defined film-fed growt
• 1970: Tyco Laboratories created Saphikon Division in Waltham 

MA and moved it to Milford NH 1978

• 1970s-1980s: Saphikon revenue mainly from licensing EFG

technology to companies such as Kyocera, RCA, Corning, Allied Signal. Licensees saw potential for silicon-on-sapphire products

• 1982: Tyco president Joe Gaziano dies and John Fort becomes

president

• Saphikon Division had less than $2M/yr revenue. Fort tried to sell Sa

found no taker

• Fort sold Saphikon to Harry LaBelle in 1985 in a deal “too good to ref

LaBelle’s intention was to resell Saphikon

• 1985: Department of Energy funded project for optical fiber for high t

and corrosive conditions

• Saphikon purchased by Cy Gregg in 1987. Tim Davis was President• 2000: Saint-Gobain buys Saphikon to manufacture sheets, rods, tub

3-dimensional shapes. Gregg forms Photran which retains exclusive manufacture sapphire fibers (for optical and structural applications)

Saphikon Company History

Information from Cy Gregg, Tim Davis, Herb Bates. EFG sapphire photo from Chalmers et al., J. Cryst. Gro

ES
Saphikon EFG Sapphire Sheets

[Photos courtesy John Locher]

m

c
• EFG sapphire fiber uses

• Optical fibers for Er-YAG lasers for medical use• Proprietary structural composites

(Fibers grown for ceramic/ceramic compositesfor National AeroSpace Plane in 1980s)

• EFG bulk sapphire uses

• Bar code scanners - largest application• Substrates for blue LEDs and laser diodes• Semiconductor manufacturing equipment 

Tubes for plasma applicatorsWindows for high temperature/corrosive environmentsElectrostatic chuck to hold wafer in place during processingEnd effector on robotic arm - grabs wafer and moves it durin

• Laser material• Scalpels and ceramic parts used inside the body• Infrared sensors components

• Kyocera EFG sapphire products available in 2003

• r, a, or c-plane sheets up to 20 cm wide x 30 cm long x 0.02-2 c• c-axis rods 0.05 to 2 cm diameter up to 1 m long• c-axis tubes• Violet sapphire jewels

Information from Cy Gregg, Tim Davis and 

Green

traffic

light
Stepanov Independently Developed 

Shaped Sapphire Crystal Growth in USSR in 1

Growth of shaped cor

began in early 197

Ef

molec

Sodium lamp envelops and

boats for making ultrapure materials

P. I. Antonov in Growth of Crystals, Vol 13 (E. I. GiNew York, 1986; V. A Borodin et al. in Growth of C

Givargizov and S. A. Grinberg, eds), Plenum, New 

Seed

Edgedefiner

Moltencharge
Stepanov Crystal Growth EFG Crystal Gro

• Stepanov method: wet

nonwettable aids shape column which shapes o

• EFG: shape of die, not 

column, controls shape 

Difference Between Stepanov and EFG Crystal 
• Crucible with seed crystal 

loaded with Verneuil crack

•Evacuate and heat to me

Seed is cooled by He flow exchanger

•After some melting of seed

flow of He to initiate crysta

•When solidification is com

decrease He flow and annslow cooldown

Sapphire Growth by Heat-Exchanger Method (

Crystal Systems
Fred Schmid and Dennis Viechnicki

in early days of HEM development

at Army Materials Research Lab in 1960s

Origins of the Heat Exchanger Method

•Early 1960s: Lafayette m

engineer Fred Schmid womanufacturing at Waterto

• Directional solidification • He-cooled arc furnace 

•After Arsenal closed, Sch

precision casting companto go to Northeastern for Science

•1967: Schmid returned to 

conceived He-cooled heaWorked with D. Viechnicksolidification of alumina• 1967: single-xtal Al2O3 i

• 1969: crack-free 3′′ xtal 

• 1969: first HEM patent i• 1971: 6′′ diameter boule 

Crystal Systems
J. Am. Ceram. So

Thermocouple
First sapphire grown in Watertown Larger boule in c

Crystal Systems

Crystals grown 1972/73 were largest diameter

sapphire ever grown at that time

Window m

6

′′ diameter 
• “By early 1971 I was convinced that the...Schmid-Viechnicki

Technique...was a breakthrough and felt that I would need tofind a market for sapphire”

•Interest in sapphire was expressed by Inselec and Insaco for

SOS (silicon-on-sapphire)

•Schmid convinces sailing buddy, Larry Ingber, and 

accountant, Dick Kanter, to invest in Crystal Systems, in which Schmid would hold 51% interest

• July 1971: Schmid purchases scrapped CVD furnace from Raytheo•Aug 1971: Crystal Systems incorporated. Schmid works on furnace •Furnace moved into space at Shetland Industrial Park in Salem• “All this time I still had my job at AMRL and was working...between 

hours a day”

• July 1972: 6′′ boule grown and 2′′ cores drilled for SOS wafers. “Al

were stressed and loaded with gas near the outside periphery becau

understand the growth process.”

•Sept 1972: Schmid leaves AMRL to work full time with 1 helper “jus

of high school.” 1st year sales <$50K to Inselec and Insaco

•Sept 1973: CSI hires 1st full-time employee; Judy Schmid handles 

Origin of Crystal Systems, Inc as told by Fred S
• “I sent our first advertising piece out as a news release...and shortly 

published (mid-1974) I got a letter from Union Carbide indicating I won their patent and offering to license their [Czochralski] technique to 

• 1975: CSI obtains patent for bubble-free sapphire and names techn

Exchanger Method” because of unique controllable heat exchanger

• 1973-78: Schmid develops Fixed Abrasive Slicing Technique for cu

wafers with diamond abrasive on a blade combined with rocking wo

• 1974: NASA selects HEM sapphire for satellites because of low opt• 1975: CSI gets government contract to grow silicon by HEM• 1977: Chandra Khattak hired from 

Brookhaven to work on Si. 1st crack-free silicon grown by HEM

• 1978: CSI moves to current quarters

and grows 1st 12′′ boule

• 1979: SBIR program initiated and 

CSI gets one of 1st contracts for laser-quality ruby

• 1980-82: HEM Si for photovoltaics• 1987-89: Ti:sapphire commercialized

Fred Schmid’s Story, continued

Crystal Systems
Crysta

Manage

Peggy Mula

Fred Schmid

Mark Felt

May

HEM 

CSI products

• sapphire

(boules up to 15′′ diameter)

• polycrystalline Si• HEM furnaces• crystal slicing machines

Crystal Systems
Fixed Abrasive Slicing Technique

Shaped 

kerf loss 

Diamon

plated ont
Growth of Near-Net-Shape Sapphire Domes by EF

Navy manufacturing technologyContract at Saphikon 1989

−1992
Polished EFG near-net-shap

viewed through crossed po

High-quality single-crystal

sapphire dome viewed through

crossed polarizers
Molybdenum pplaced in moltecharge for HEM at Crystal Syst

Growth of Near-Net-Shape Sapphire Domes by HE

Navy contract 

As-grown blanks Polished dome and as-g
Once uone dohogged cylinde

Then scoopinvented anmore dometaken from volume

Crystal Systems

Precision Lapping and Optical Co.
Diamond-impregnated scooping tools

Scooped dome blanks

• Rotate sapphire rod and 

in opposite directions to cdiameter with the small swhose outside edge is thcutting surface

• Then use larger tool to cu

diameter of the dome. Inof tool is active cutting su

• Small cylindrical plug is l

of dome connecting it to in stack. Light force breaapart at end of scooping

Scooping domes at Cryst
Hottest

Coolest

Gradient Solidification

Sapphire Growth

at Rotem Industries, Israel

Founded in 1969

Pyrometer

Mo radiation shield

Crucible lidSapphire

Mo crucible

3-phase graphiteheating element

Powercontrol

Vacuumsystem

Seedcrystal

Atara Horowitz
Atara Horowitz 

Rotem furnaces

Polished As-grown dome

Dome through

crossed polarizers

Sapphire

dome

As-grow

c-a
S & R Rubicon S

Russian American Com

Horizontal directional solidification

(Bridgman growth)

Stepanov (EFG) growth

Verneuil grow

S & R Rubicon a

Kyropoulos growt

for highest crysta
Sapphire from Atlas

Russian Research and Production Company

Kyropoulos growth method, also called GOI in Russia
Verneuil Sapphire from Atlas

Russian Research and Production Company
Acknowledgements:• Kurt Nassau, Gems Ma

Bell Labs

• Fred Schmid and Chand

Crystal Systems

• Herb Bates, Cy Gregg, a

Saphikon

• Larry Rothrock

Photran and Union Ca

• Atara Horowitz

Rotem

If he didn’t talk so much, he would have finished his ice cream by now