CA1171341A - Method for producing gadolinium garnet - Google Patents
Method for producing gadolinium garnetInfo
- Publication number
- CA1171341A CA1171341A CA000349487A CA349487A CA1171341A CA 1171341 A CA1171341 A CA 1171341A CA 000349487 A CA000349487 A CA 000349487A CA 349487 A CA349487 A CA 349487A CA 1171341 A CA1171341 A CA 1171341A
- Authority
- CA
- Canada
- Prior art keywords
- iridium
- crucible
- melt
- cover member
- boule
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
- C30B29/22—Complex oxides
- C30B29/28—Complex oxides with formula A3Me5O12 wherein A is a rare earth metal and Me is Fe, Ga, Sc, Cr, Co or Al, e.g. garnets
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Soft Magnetic Materials (AREA)
Abstract
METHOD FOR PRODUCING
GADOLINIUM GALLIUM GARNET
Abstract of the Disclosure Method for producing essentially iridium-free unicrystalline gadolinium gallium garnet from a melt of gadolinium and gallium oxides contained in an iridium crucible.
GADOLINIUM GALLIUM GARNET
Abstract of the Disclosure Method for producing essentially iridium-free unicrystalline gadolinium gallium garnet from a melt of gadolinium and gallium oxides contained in an iridium crucible.
Description
:~7~34~
The present invention relates to a methot for producing massive unicrystalline gadolinium gallium garnet material. More particularly, the present invention is directed to a method for producing such material from an oxide melt contained ln an iridium crucible.
Unicry~talline gadolinium gallium garnet material în massive form is produced following the well known Czochralski technique by pulling a seed rod from a melt of Gd203 and Ga203 in a molar ratio of 3:5. The melt is most ususally contained in an iridium crucible, iridium being considered the most desirable metal for this purpose on account of its known physical and chemical properties.
Also, it is kno~n to provide a cover member or lid formed of iridium for the iridium crucible which acts as a radiation heat shield. The ~adolinium gallium garnet i~ produced in the form of an elongate boule of circular cross-section which is subsequently sawed into wa~ers for use as sub-strates in electronic applications such as the epitaxial growth of iron garnet film. It is very important that ~hese sub~trates, and hence the crystal from which they are formed, be free of impurities, e.g. iridium inclusions. This is so since such incluslons will propagate into epitaxial layers formed on crystalline substrates with well known detrimental effects.
'~e.
The present invention relates to a methot for producing massive unicrystalline gadolinium gallium garnet material. More particularly, the present invention is directed to a method for producing such material from an oxide melt contained ln an iridium crucible.
Unicry~talline gadolinium gallium garnet material în massive form is produced following the well known Czochralski technique by pulling a seed rod from a melt of Gd203 and Ga203 in a molar ratio of 3:5. The melt is most ususally contained in an iridium crucible, iridium being considered the most desirable metal for this purpose on account of its known physical and chemical properties.
Also, it is kno~n to provide a cover member or lid formed of iridium for the iridium crucible which acts as a radiation heat shield. The ~adolinium gallium garnet i~ produced in the form of an elongate boule of circular cross-section which is subsequently sawed into wa~ers for use as sub-strates in electronic applications such as the epitaxial growth of iron garnet film. It is very important that ~hese sub~trates, and hence the crystal from which they are formed, be free of impurities, e.g. iridium inclusions. This is so since such incluslons will propagate into epitaxial layers formed on crystalline substrates with well known detrimental effects.
'~e.
- 2 ~
t~ 13 ~
. . 12196 It has been found ehat the above-noted iridium inclusions occur with significant frequency in ~he lower section of Czochralski grown boules, i.e. in the last grown section of the boule.
It is, therefore, an object of the present invention to provide a method for producing massive - -unicrystalline gadolinium gallium garnet boules which are essentially free of iridium inclusions.
Other objects will be apparent from the following description and claims taken in conjunction with the drawing in which Figure 1 shows an apparatus suitable for ~he practice of the present invention and :: Figure 2 illuatrates a unicrystalline boule of substantially circular cross-section produced by the prac~ice .- of the present invention Figure 3~a) shows the crucible arrangement of Figure 1 prior to the commencement of crystal grow~h and . Figures 3(b) and 3(cj show the arrangement of Figure 3(a) during crystal growth.
Dhe me hod of the present invention for producing virtually perfect unicrystalline gadolinium gallium garnet boules of substantially circular cross-section involves
t~ 13 ~
. . 12196 It has been found ehat the above-noted iridium inclusions occur with significant frequency in ~he lower section of Czochralski grown boules, i.e. in the last grown section of the boule.
It is, therefore, an object of the present invention to provide a method for producing massive - -unicrystalline gadolinium gallium garnet boules which are essentially free of iridium inclusions.
Other objects will be apparent from the following description and claims taken in conjunction with the drawing in which Figure 1 shows an apparatus suitable for ~he practice of the present invention and :: Figure 2 illuatrates a unicrystalline boule of substantially circular cross-section produced by the prac~ice .- of the present invention Figure 3~a) shows the crucible arrangement of Figure 1 prior to the commencement of crystal grow~h and . Figures 3(b) and 3(cj show the arrangement of Figure 3(a) during crystal growth.
Dhe me hod of the present invention for producing virtually perfect unicrystalline gadolinium gallium garnet boules of substantially circular cross-section involves
3~1 the following steps:
(i) forming a melt by heating a mixture of Gd203 and Ga203 in a molar ratio of 3:5 in an iridium crucible having an iridium cover member with a circular opening positionec above the surface of ~he melt only slightly larger than the cross-section of the boule to be produced the melt being at a temperature in the range of 1700 to 1800C.
(ii) inserting a seed rod of unicrystalline gadolinium gallium garnet through said circular opening in said iridiu~ cover member into the melt, (iii) providing an ambient atmosphere of nitrogen : containing from about O.S~/~ to 3~h oxygen by volume (iv~ withdrawing the seed rod from the melt such that gadolinium gallium garnet material is solidified and crystallizPd on the seed rod to form a massive unicrystalline boule ; produc e of increasing length and havinga subs~antially circular cross-section slightly less ~han the ~ircular opening in said iridium cover member, said boul~ passing 3~ -through said circular opening in said iridium cover member as ~he length of said boule ~ncreases to substantially enclose the surface of the melt in said iridium crucible in a compa~tment defined by the walls of said crucible, said iridium cover member, and the peripheral side of said boule, and (v) introducing a continuous flow of nitr.ogen con~aining from about 0.5 to 3% by volume oxygen into said compartment at a rate sufficient ~o maintain an atmosphere in said compartment of nitrogen containing about 0.5 to 3% by volume oxygen.
The improvement of the present invention with respect to previou. growth techniques using an iridium : crucible and lridJum cover member resides in the continuous .main~enance of an atmosphere of~ni~rogen and aboue 0.5% to 3%, preferably 2% oxygen in the region within the crucible contiguous to the melt surface, crystal growth interface and ~he adjacently located bo~tom surface of the iridium cover and the inner surface of the iridLum crucible which is above the melt.
With reference to Figure 1, there is illustrated a chamber 1 for enclosing crystal pulling apparatus and the ambient gaseous atmosphere. ~ithln chamber l, a m~lt 9 of Gd203 and Ga203 in a molar ratio of 3:5 is contained ~17~341 ~2196 in a crucible 8 which is fabric~ted from iridium. A
cover member or lid 16, formed of iridium, having a central circular aperture 17 rests on top the crucible 8 and ehe lower surface ehereof acts as a radiation shield in a manner known to the art to reduce heat loss from che melt 9. The central circ~Ylar aperture 17 is designed to be only slightly larger in cross-section than the circular cross-section of the boule to be produced, represented at 25 in Fi'gure 2. The crucible 8 is bounded on its sides and bottom with insulation 15.
The insulation is preferably zirconia and serves to:
reduce the power required to suseain the melt 9; reduce thermal gradients along the crucible; and to dampen temperature fluceuations arising from line voltage fluctuations, convective cooling effects from the atmosphere, ~s well as other distrubances. ~ollow tubing 11 forms an aperture through which the temperature of the bottom of the crucible 8 can be determined by, for example, ~ radia~ion pyrometer fo&used Oll the center of the bottom of the crucible.
A ceramic washer 4, fabrica~ed from alumina, for example, is supported by eubing 5 preferably of zirconia. The washer 4 serves as a secondary radiation shield and to restrict the convective currents of ehe atmosphere against entering the ~op o the crucible and reaching the growing crystal 7. Thus, it serves to reduce . ~7~3~ ~ 12196 .
the vertical tempera~ure gradients in the vicinity of the growing crystal and to augment ehe effects of the washe.r 16.
Sleeve 6, ~ormed of silicon dioxide, ~or example, ~erves ~o contain the insulation 15 and serves as a par~ of the insulating assembly surroundlng ~he crucible 8. The tubing 5 which serves to support ehe washer 4 also functions as a part of the ~nsulating system.
The crucible 8 and its surrounding insulating assembly rests on a ceramic pedeseal 12 composed of, for example, zirconium oxide (ZrO2). The entire assembly is enclosed in a bell jar 3 sealed to a base plate 13.
The base plate 13 is composed of any suitabl~ material such as fcr example silicone-bonded fiber glass. The major portion of the ambient gas atmosphere intended for the inside of the bell ~ar 3, i.e. a gas aemosphçre . non-reactive with the melt in the crucible, e.g. nitrogen, : with 0.5% ~o 3% preferably 27, by volume oxygen, is intro-duced in a continuous flow into sight ~ube 14 which communicates with tubing 11. The gas introduced into belL jar 3 exits through the hole 18 in the bell jar 3 through which the seed rod is inserted. Rod 2 e.g. ma~e o~ A~203 has a 5en~ p~r~lon2'~he form of unicrystalline gadolinium gallium garnet material having its longitudinal axis 20 common with the growth axis 30 of crystal 7 and ehe orientation of the unicrys~alline material of seed ~ is a predetermined 3~ ~
v 12196 orientation depending on the ultimate industrial use.
Such a seed rod can be routinely prepared and results in the produceion of a massive unicrystalline material.
Using the above-described apparatus, the temperature of the melt is maintained in the range of 1700 to 1800C and a unicrystalline mass is pulled from the melt to pro~ide a circular cross-section of increasing length, e.g. 6-18 inches and about 3 inches in diameter, following procedures known to the art as exemplified by U.S. patent 3,715,194. The resulting unicrystalline boule mater~al represeneed at 25 in Figure 2 has a substantially circular uniform cross section.
With reference to Figure 3(a), thls view : shows the iridium crucible 8, iridium lid 16, melt 9 and seed rod 7 shown in Figure 1 prior to crystal pulling.
At such time, the gaseous atmosphere withLn the iridium crucible 8 above melt 9 is essentially the same as the desired ambient atmosphere in bell jar 1 which is introduced via tubing 11 of Figure 1. Figure 3(b~ shows ~he arrangement of Figure 3(a) after crystal pulling has progressed and the length of the boule 25 being produced has increased so as to pass through aperture 17 of iridium lid 16. ~or this condition, which persists until the desired boule length is produced, e.g. 6 to 18 inehes, a compartment 35 is ~ormed which is defined by the lower qurface of iridium lid 17, the inner wall 36 of ~ 3~ 1 12196 iridium crucible 8 and the peripheral side of boule 25 ~nd the melt surface. This compartment substantially encloses the sur~ace of melt 9 therein and the ambient aemosphere in compartment 35 is the actual ambient atmosphere to which the melt 9, crystal growch interfacc 40 and the adjacent iridium surfaces. are exposed. It has been discovered, as par~ of the present invention, that for the condition represented in Figure 3(b), which prevails during most of the crystal pulling procedure, the ambient atmosphere in compartment 35, unless replenished, becomes increasingly depleted of oxygen relative to the ambient atmosphere in bell jar 3 since the only exposure to the desired ambien~
atmosphere in bell jar 3 is via the small open-ng 17' betwe~n the sides of boule 25 and lid 16 which does not permit complete replenishment or homogenization of the atmosphere in compartment 35. That is to say, the atmosphere in compartment 35 is essen~ially isolaeed from the ambiant atmosphere of bell jar 3. The increasing deple~ion of oxygen in compartment 35 (unless replenished) and hence at the melt surface and the growth interface 40 leads to the increasing presence of iridium inclusions in the boule with the result that the last grown part of the boule, indicated a~ 50 in Figure 2, the growth inter~
face of which was subjected to the most severe oxygen depl~tion ef~ec~, contain~ an undesirably large number _ g _ ~17~3~1 12196 of iridium inclusions, e.g. as much as 100/cm3.
The inclusions, as is known to the art, are discrete metallic platelets or particles 1-20 microns in tiameter. In the present inven~ion, this undesirable effect is avoided by introducing into compartm~nt 35 a continuous flow of nitrogen containing from about O.5 to 3%, preferab`ly by 2% volume oxygen, e.g. by way o~ iridium tube 47 which is shown communicating with compartment 35 through the iridium cover member, or lid 16. The rate of gas flow through tube 47 into compartment 35 is such that the desired amblent gas atmosphere as in bell jar 3 is maint~ined in compartment 35 over the surface of the melt and at growth in~erface 40 throughout the crystal pulling procedure. As a result of this practice, the presence of undesLrable irLdium inclusions in the boule 25 is essentially avoided. The replenishing gas flow is, aq shown in the drawing, preferably introducet through an aperture in iridium lld 16 which is located close to the side w811 of the crucible so that the replenishing gas flow esseneially continyously flushes compartment 35 to ensure the presence of the deslred ambient pressure in compartment 35. Other arrangements for intro-ducing replenishing ~low in~o compartme~t 35 m~y 3~ ~ l2l96 be used,'e.g. through the crucible side wall to achieve the same flushing effect.
A suitable ra~e of gas flow can be readily determined for the particular apparatus involved. For example, knowing the volume of the compartment 35, Vc, by measurement of calculation, for such volume, Vc, a suitable gas flow rate can be expressed as from O.2 Vc to 15 Vc per minute. That is, if the volume of the compartment Vc is one cu. ft., a suitable gas flow range is from 0.2 to 15 cu. ft. per minute. Higher flow rates may possibly be used provided that the melt surface is not disturbed thereby. Since the compzrtment volume, Vc, necessarily increases as the melt lowers in the crucible during crystal gro~th this should be considered when selecting a gas flow rate.
~ 71 3~ 1 lZ196 EXAMPLE I
About 11,500 grams of Gd203 and &a203 in a molar ratio of 3:5 (3.02:4.98) were placed in an iridium crucible having an inside diameter of 5.3 inches; a wall thickness of 0.1 inch and a .eigh of 5.75 inches. An iridium cover 5.5 inch diameter, 0.1 inch thick having a central circular aperture of 3.5 inch diameter was provided on top of the iridium crucible. The crucible was placed ~within an 8 turn induction hcating aoil having an I.D. of 7.5 inches. The crucible 9 tood ~.
on a pedestal containing packed zirconia granules while the space b@tween the coil and the crucible was aLso packed wi eh zirconia granules. This entire apparatus was enclosed in an aluminum bell jar (28 cu. ft) having an aperture at its top. A nitrogen a~mosphere:
containing about 2% by volume oxygen was:provided inside th bell jar by means of an inlet located beneath the crucible and remote from the crucible.
The gas flow was 40 cu.ft~. per hour. An iridium tube (.25 inch I.D.) located l inch from the crucible side wall communicated with the interior of the crucible through the lid~ For this Example there was no gas flow through the iridium tube.
11713~1 12196 The induction heating coil was energized from a well known R.F. induction heating unit and the p~wer was increased until the induced current in ~he iridium crucible heated it to a "white heat".
Conductive heat from the iridium crucible formed a melt in the crucible. The height of the crucible waLl above the melt at this time was about 0.5 inch.
A unicrystalline gadolinium gallium garnet seed 0.375 inch diameter (Clll~ orientation? was lowered through the aperture in the iridium cover until it contacted ; the sur~ace of the melt. The seed was then withdrawn from the melt a~ about~ 0.3 inch per hour for 30 hours.
The height of the crucible wall above the mele when growth was terminated was 4.5 inches. A 9 inch long boule of 3.2 inch circular cross-section was obtained which contained numerous iridium inclusions (at least 100/cm2) in the bo~eom, i.e. last formed 1/3 of the boule.
EXAMPLE II
Essentially the same procedure as ln Example I was followed except that nitrogen gas containing 2% oxygen by volume was caused to flow continuously through ~he iridium tube inco the crucible at a rata of 10 cu. ft. per hour. A
boule 3.2 inch in diameter and about 8 inches long 3~
- i21g6 was produced which had few iridium inclusions (not more than S/cm3) throughoue its length.
EXAMPLE III
Essentially the same procedure as in Example I was followed except that nitrogen gas con~aining 2% oxygen by volume was c used to flow continuously through the iridium tube into the crucible at a rate of 2 cu.ft. per hour. A boule 3.2 inch in diameter and about 8 inches long was produced which had few iridium inclusions (not more than 5/cm3) throughout its length.
`:
(i) forming a melt by heating a mixture of Gd203 and Ga203 in a molar ratio of 3:5 in an iridium crucible having an iridium cover member with a circular opening positionec above the surface of ~he melt only slightly larger than the cross-section of the boule to be produced the melt being at a temperature in the range of 1700 to 1800C.
(ii) inserting a seed rod of unicrystalline gadolinium gallium garnet through said circular opening in said iridiu~ cover member into the melt, (iii) providing an ambient atmosphere of nitrogen : containing from about O.S~/~ to 3~h oxygen by volume (iv~ withdrawing the seed rod from the melt such that gadolinium gallium garnet material is solidified and crystallizPd on the seed rod to form a massive unicrystalline boule ; produc e of increasing length and havinga subs~antially circular cross-section slightly less ~han the ~ircular opening in said iridium cover member, said boul~ passing 3~ -through said circular opening in said iridium cover member as ~he length of said boule ~ncreases to substantially enclose the surface of the melt in said iridium crucible in a compa~tment defined by the walls of said crucible, said iridium cover member, and the peripheral side of said boule, and (v) introducing a continuous flow of nitr.ogen con~aining from about 0.5 to 3% by volume oxygen into said compartment at a rate sufficient ~o maintain an atmosphere in said compartment of nitrogen containing about 0.5 to 3% by volume oxygen.
The improvement of the present invention with respect to previou. growth techniques using an iridium : crucible and lridJum cover member resides in the continuous .main~enance of an atmosphere of~ni~rogen and aboue 0.5% to 3%, preferably 2% oxygen in the region within the crucible contiguous to the melt surface, crystal growth interface and ~he adjacently located bo~tom surface of the iridium cover and the inner surface of the iridLum crucible which is above the melt.
With reference to Figure 1, there is illustrated a chamber 1 for enclosing crystal pulling apparatus and the ambient gaseous atmosphere. ~ithln chamber l, a m~lt 9 of Gd203 and Ga203 in a molar ratio of 3:5 is contained ~17~341 ~2196 in a crucible 8 which is fabric~ted from iridium. A
cover member or lid 16, formed of iridium, having a central circular aperture 17 rests on top the crucible 8 and ehe lower surface ehereof acts as a radiation shield in a manner known to the art to reduce heat loss from che melt 9. The central circ~Ylar aperture 17 is designed to be only slightly larger in cross-section than the circular cross-section of the boule to be produced, represented at 25 in Fi'gure 2. The crucible 8 is bounded on its sides and bottom with insulation 15.
The insulation is preferably zirconia and serves to:
reduce the power required to suseain the melt 9; reduce thermal gradients along the crucible; and to dampen temperature fluceuations arising from line voltage fluctuations, convective cooling effects from the atmosphere, ~s well as other distrubances. ~ollow tubing 11 forms an aperture through which the temperature of the bottom of the crucible 8 can be determined by, for example, ~ radia~ion pyrometer fo&used Oll the center of the bottom of the crucible.
A ceramic washer 4, fabrica~ed from alumina, for example, is supported by eubing 5 preferably of zirconia. The washer 4 serves as a secondary radiation shield and to restrict the convective currents of ehe atmosphere against entering the ~op o the crucible and reaching the growing crystal 7. Thus, it serves to reduce . ~7~3~ ~ 12196 .
the vertical tempera~ure gradients in the vicinity of the growing crystal and to augment ehe effects of the washe.r 16.
Sleeve 6, ~ormed of silicon dioxide, ~or example, ~erves ~o contain the insulation 15 and serves as a par~ of the insulating assembly surroundlng ~he crucible 8. The tubing 5 which serves to support ehe washer 4 also functions as a part of the ~nsulating system.
The crucible 8 and its surrounding insulating assembly rests on a ceramic pedeseal 12 composed of, for example, zirconium oxide (ZrO2). The entire assembly is enclosed in a bell jar 3 sealed to a base plate 13.
The base plate 13 is composed of any suitabl~ material such as fcr example silicone-bonded fiber glass. The major portion of the ambient gas atmosphere intended for the inside of the bell ~ar 3, i.e. a gas aemosphçre . non-reactive with the melt in the crucible, e.g. nitrogen, : with 0.5% ~o 3% preferably 27, by volume oxygen, is intro-duced in a continuous flow into sight ~ube 14 which communicates with tubing 11. The gas introduced into belL jar 3 exits through the hole 18 in the bell jar 3 through which the seed rod is inserted. Rod 2 e.g. ma~e o~ A~203 has a 5en~ p~r~lon2'~he form of unicrystalline gadolinium gallium garnet material having its longitudinal axis 20 common with the growth axis 30 of crystal 7 and ehe orientation of the unicrys~alline material of seed ~ is a predetermined 3~ ~
v 12196 orientation depending on the ultimate industrial use.
Such a seed rod can be routinely prepared and results in the produceion of a massive unicrystalline material.
Using the above-described apparatus, the temperature of the melt is maintained in the range of 1700 to 1800C and a unicrystalline mass is pulled from the melt to pro~ide a circular cross-section of increasing length, e.g. 6-18 inches and about 3 inches in diameter, following procedures known to the art as exemplified by U.S. patent 3,715,194. The resulting unicrystalline boule mater~al represeneed at 25 in Figure 2 has a substantially circular uniform cross section.
With reference to Figure 3(a), thls view : shows the iridium crucible 8, iridium lid 16, melt 9 and seed rod 7 shown in Figure 1 prior to crystal pulling.
At such time, the gaseous atmosphere withLn the iridium crucible 8 above melt 9 is essentially the same as the desired ambient atmosphere in bell jar 1 which is introduced via tubing 11 of Figure 1. Figure 3(b~ shows ~he arrangement of Figure 3(a) after crystal pulling has progressed and the length of the boule 25 being produced has increased so as to pass through aperture 17 of iridium lid 16. ~or this condition, which persists until the desired boule length is produced, e.g. 6 to 18 inehes, a compartment 35 is ~ormed which is defined by the lower qurface of iridium lid 17, the inner wall 36 of ~ 3~ 1 12196 iridium crucible 8 and the peripheral side of boule 25 ~nd the melt surface. This compartment substantially encloses the sur~ace of melt 9 therein and the ambient aemosphere in compartment 35 is the actual ambient atmosphere to which the melt 9, crystal growch interfacc 40 and the adjacent iridium surfaces. are exposed. It has been discovered, as par~ of the present invention, that for the condition represented in Figure 3(b), which prevails during most of the crystal pulling procedure, the ambient atmosphere in compartment 35, unless replenished, becomes increasingly depleted of oxygen relative to the ambient atmosphere in bell jar 3 since the only exposure to the desired ambien~
atmosphere in bell jar 3 is via the small open-ng 17' betwe~n the sides of boule 25 and lid 16 which does not permit complete replenishment or homogenization of the atmosphere in compartment 35. That is to say, the atmosphere in compartment 35 is essen~ially isolaeed from the ambiant atmosphere of bell jar 3. The increasing deple~ion of oxygen in compartment 35 (unless replenished) and hence at the melt surface and the growth interface 40 leads to the increasing presence of iridium inclusions in the boule with the result that the last grown part of the boule, indicated a~ 50 in Figure 2, the growth inter~
face of which was subjected to the most severe oxygen depl~tion ef~ec~, contain~ an undesirably large number _ g _ ~17~3~1 12196 of iridium inclusions, e.g. as much as 100/cm3.
The inclusions, as is known to the art, are discrete metallic platelets or particles 1-20 microns in tiameter. In the present inven~ion, this undesirable effect is avoided by introducing into compartm~nt 35 a continuous flow of nitrogen containing from about O.5 to 3%, preferab`ly by 2% volume oxygen, e.g. by way o~ iridium tube 47 which is shown communicating with compartment 35 through the iridium cover member, or lid 16. The rate of gas flow through tube 47 into compartment 35 is such that the desired amblent gas atmosphere as in bell jar 3 is maint~ined in compartment 35 over the surface of the melt and at growth in~erface 40 throughout the crystal pulling procedure. As a result of this practice, the presence of undesLrable irLdium inclusions in the boule 25 is essentially avoided. The replenishing gas flow is, aq shown in the drawing, preferably introducet through an aperture in iridium lld 16 which is located close to the side w811 of the crucible so that the replenishing gas flow esseneially continyously flushes compartment 35 to ensure the presence of the deslred ambient pressure in compartment 35. Other arrangements for intro-ducing replenishing ~low in~o compartme~t 35 m~y 3~ ~ l2l96 be used,'e.g. through the crucible side wall to achieve the same flushing effect.
A suitable ra~e of gas flow can be readily determined for the particular apparatus involved. For example, knowing the volume of the compartment 35, Vc, by measurement of calculation, for such volume, Vc, a suitable gas flow rate can be expressed as from O.2 Vc to 15 Vc per minute. That is, if the volume of the compartment Vc is one cu. ft., a suitable gas flow range is from 0.2 to 15 cu. ft. per minute. Higher flow rates may possibly be used provided that the melt surface is not disturbed thereby. Since the compzrtment volume, Vc, necessarily increases as the melt lowers in the crucible during crystal gro~th this should be considered when selecting a gas flow rate.
~ 71 3~ 1 lZ196 EXAMPLE I
About 11,500 grams of Gd203 and &a203 in a molar ratio of 3:5 (3.02:4.98) were placed in an iridium crucible having an inside diameter of 5.3 inches; a wall thickness of 0.1 inch and a .eigh of 5.75 inches. An iridium cover 5.5 inch diameter, 0.1 inch thick having a central circular aperture of 3.5 inch diameter was provided on top of the iridium crucible. The crucible was placed ~within an 8 turn induction hcating aoil having an I.D. of 7.5 inches. The crucible 9 tood ~.
on a pedestal containing packed zirconia granules while the space b@tween the coil and the crucible was aLso packed wi eh zirconia granules. This entire apparatus was enclosed in an aluminum bell jar (28 cu. ft) having an aperture at its top. A nitrogen a~mosphere:
containing about 2% by volume oxygen was:provided inside th bell jar by means of an inlet located beneath the crucible and remote from the crucible.
The gas flow was 40 cu.ft~. per hour. An iridium tube (.25 inch I.D.) located l inch from the crucible side wall communicated with the interior of the crucible through the lid~ For this Example there was no gas flow through the iridium tube.
11713~1 12196 The induction heating coil was energized from a well known R.F. induction heating unit and the p~wer was increased until the induced current in ~he iridium crucible heated it to a "white heat".
Conductive heat from the iridium crucible formed a melt in the crucible. The height of the crucible waLl above the melt at this time was about 0.5 inch.
A unicrystalline gadolinium gallium garnet seed 0.375 inch diameter (Clll~ orientation? was lowered through the aperture in the iridium cover until it contacted ; the sur~ace of the melt. The seed was then withdrawn from the melt a~ about~ 0.3 inch per hour for 30 hours.
The height of the crucible wall above the mele when growth was terminated was 4.5 inches. A 9 inch long boule of 3.2 inch circular cross-section was obtained which contained numerous iridium inclusions (at least 100/cm2) in the bo~eom, i.e. last formed 1/3 of the boule.
EXAMPLE II
Essentially the same procedure as ln Example I was followed except that nitrogen gas containing 2% oxygen by volume was caused to flow continuously through ~he iridium tube inco the crucible at a rata of 10 cu. ft. per hour. A
boule 3.2 inch in diameter and about 8 inches long 3~
- i21g6 was produced which had few iridium inclusions (not more than S/cm3) throughoue its length.
EXAMPLE III
Essentially the same procedure as in Example I was followed except that nitrogen gas con~aining 2% oxygen by volume was c used to flow continuously through the iridium tube into the crucible at a rate of 2 cu.ft. per hour. A boule 3.2 inch in diameter and about 8 inches long was produced which had few iridium inclusions (not more than 5/cm3) throughout its length.
`:
Claims (2)
1. In a method for producing virtually perfect unicrystalline gadolinium gallium garnet boules of substantially circular cross-section by (i) forming a melt by heating a mixture of Gd2O3 and Ga2O3 in a molar ratio of 3:5 in an iridium crucible having an iridium cover member wich a circular opening only slightly larger than the cross-section of the boule to be produced said iridium cover member being positioned above the surface of the melt and resting on said crucible, (ii) inserting a seed rod of unicrystalline gadolinium gallium garnet through said circular opening in said iridium cover member into the melt, (iii) providing an ambient atmosphere of nitrogen containing about 0.5 to 3% by volume oxygen surrounding said covered iridium crucible, (iv) withdrawing the seed rod from the melt such that gadolinium gallium garnet material is solidified and crystallized on the seed rod to form a virtually perfect massive unicrystalline boule product of increasing length and a substantially circular corss-section which attains a diameter only slightly less than that of the circular opening in said iridium cover member, said boule passing through said circular opening in said iridium cover member as the seed rod and boule are withdrawn from the melt to establish only a slight opening between the peripheral side of said boule and said iridium cover member and substantially enclose the surface of the melt in said iridium crucible in a compart-ment defined by the walls of said crucible, said iridium cover member, the peripheral side of said circular cross-section boule and the melt surface.
the improvement which comprises introducing a con-tinuous flow of nitrogen gas containing about 0.5 to 3% oxygen into said compartment at a rate sufficient to maintain about 0.5 to 3% by volume of oxygen in said compartment said flow of gas being introduced into said compartment at a location close to a wall of said crucible and existing said compartment at the slight opening between the peri-pheral side wall of said boule and said iridium cover member.
the improvement which comprises introducing a con-tinuous flow of nitrogen gas containing about 0.5 to 3% oxygen into said compartment at a rate sufficient to maintain about 0.5 to 3% by volume of oxygen in said compartment said flow of gas being introduced into said compartment at a location close to a wall of said crucible and existing said compartment at the slight opening between the peri-pheral side wall of said boule and said iridium cover member.
2. Method in accordance with claim 1 wherein said flow of gas is introduced through an aperture in said iridium cover member.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US2921679A | 1979-04-12 | 1979-04-12 | |
| US029,216 | 1979-04-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1171341A true CA1171341A (en) | 1984-07-24 |
Family
ID=21847874
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000349487A Expired CA1171341A (en) | 1979-04-12 | 1980-04-09 | Method for producing gadolinium garnet |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5918360B2 (en) |
| CA (1) | CA1171341A (en) |
| CH (1) | CH646402A5 (en) |
| DE (1) | DE3013045C2 (en) |
| FR (1) | FR2453916A1 (en) |
| GB (1) | GB2047113B (en) |
| NL (1) | NL8002144A (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS605094A (en) * | 1983-06-13 | 1985-01-11 | Shin Etsu Chem Co Ltd | Method for manufacturing gallium garnet single crystal |
| FR2548689B1 (en) * | 1983-07-07 | 1985-11-08 | Crismatec | PROCESS FOR PRODUCING BISMUTH GERMANATE MONOCRYSTALS WITH HIGH SCINTILLATION YIELD |
| US6451711B1 (en) * | 2000-05-04 | 2002-09-17 | Osemi, Incorporated | Epitaxial wafer apparatus |
| US6936900B1 (en) | 2000-05-04 | 2005-08-30 | Osemi, Inc. | Integrated transistor devices |
| US7187045B2 (en) | 2002-07-16 | 2007-03-06 | Osemi, Inc. | Junction field effect metal oxide compound semiconductor integrated transistor devices |
| JP6134379B2 (en) * | 2012-04-24 | 2017-05-24 | フォルシュングスフェアブント・ベルリン・アインゲトラーゲナー・フェライン | Method and apparatus for growing indium oxide (In2O3) single crystal and indium oxide (In2O3) |
| CN104313693B (en) * | 2014-09-19 | 2017-01-18 | 北京雷生强式科技有限责任公司 | Yttrium aluminum garnet laser crystal doped growth device, crystal growth furnace and preparation method thereof |
| WO2021031139A1 (en) | 2019-08-21 | 2021-02-25 | 眉山博雅新材料有限公司 | Multi-component garnet-structured scintillation crystal growth method and equipment |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3723599A (en) * | 1971-08-18 | 1973-03-27 | Bell Telephone Labor Inc | Technique for growth of single crystal gallium garnet |
| CA1080589A (en) * | 1976-06-24 | 1980-07-01 | Union Carbide Corporation | Method for producing single crystal gadolinium gallium |
-
1980
- 1980-03-28 GB GB8010437A patent/GB2047113B/en not_active Expired
- 1980-04-02 JP JP55042083A patent/JPS5918360B2/en not_active Expired
- 1980-04-03 DE DE3013045A patent/DE3013045C2/en not_active Expired
- 1980-04-09 CA CA000349487A patent/CA1171341A/en not_active Expired
- 1980-04-11 CH CH282380A patent/CH646402A5/en not_active IP Right Cessation
- 1980-04-11 FR FR8008145A patent/FR2453916A1/en not_active Withdrawn
- 1980-04-11 NL NL8002144A patent/NL8002144A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| JPS55136200A (en) | 1980-10-23 |
| GB2047113B (en) | 1983-08-03 |
| GB2047113A (en) | 1980-11-26 |
| JPS5918360B2 (en) | 1984-04-26 |
| DE3013045A1 (en) | 1980-10-16 |
| DE3013045C2 (en) | 1983-11-03 |
| NL8002144A (en) | 1980-10-14 |
| FR2453916A1 (en) | 1980-11-07 |
| CH646402A5 (en) | 1984-11-30 |
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