CN1252323C - Process for growing calcium borate mono crystal by melt drawing - Google Patents
Process for growing calcium borate mono crystal by melt drawing Download PDFInfo
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- CN1252323C CN1252323C CN 03157326 CN03157326A CN1252323C CN 1252323 C CN1252323 C CN 1252323C CN 03157326 CN03157326 CN 03157326 CN 03157326 A CN03157326 A CN 03157326A CN 1252323 C CN1252323 C CN 1252323C
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Abstract
The present invention relates to a melt drawing method for growing calcium borate monocrystals. The present invention has the steps that 1, a Ca3 (BO3)2 powder phase is prepared (CaCO3 pwoder and B2O3 pwoder are uniformly mixed and are heated for 24 to 36 hours under 1200 DEG C, then, the mixture is cooled to room temperature); 2, Ca3 (BO3)2 monocrystals are grown by the melt drawing method; 2, the Ca3 (BO3)2 powder obtained in the first step is arranged in a platinum copple which is arranged in a drawing monocrystal furnace, the temperature is raised to 1500 to 1550 DEG C, the constant temperature is maintained for 1 to 5 hours, and then, the temperature is lowered to 1465 to 1480 DEG C; after the temperature is balanced, directional seed crystals are adopted and are delivered, and the constant temperature is maintained for 1 to 2 hours; the temperature is slowly lowered at a cooling speed of 0.5 to 3 DEG C /hour, and the crystals start to grow; simultaneously, the crystals rotate at a speed of 20 to 60 circles/minute, and the crystals are drawn at a speed of 1 to 3 mm/hour; after the crystals are grown to a desired dimension, the crystals are lifted off the liquid level, and the temperature is lowered to room temperature at a speed of 50 to 60 DEG C /hour; the calcium borate monocrystals are obtained. The Ca3 (BO3)2 crystals grown by the method can obtained monocrystals with large size and high quality. The present invention has the advantages of simple technical process, easy operation, high growth speed and low cost.
Description
Technical Field
The invention relates to a single crystal growth method, in particular to a melt pulling growth method of calcium borate single crystal.
Background
The birefringent crystal is used as a functional material in modern photoelectric technology, has been widely applied in the technical fields of optical polarization, optical modulation and nonlinear optics, and is particularly used for manufacturing polarizing prisms, phase delay devices, electro-optical modulation devices and optical communication elements for various purposes, such as optical isolators, circulators, beam shifters and the like, and has important application value. There are hundreds of crystals with birefringence effect known at present, but only a dozen of crystals can be actually used. The birefringent materials commonly used are mainly natural calcite (CaCO)3) Crystalline, rutile (TiO)2) Crystal, YVO4Crystal of LiNbO3Crystals, and the recently reported α -BaB2O4And (4) crystals.
Calcite crystals mainly exist in a natural form, are difficult to artificially synthesize, are small in general size and high in impurity content, and cannot meet the requirements of large-size optical polarizing elements; the crystal has low hardness, is completely cleaved along {10-11}, is difficult to process and has low crystal utilization rate. Rutile crystals are also predominant in the natural form, difficult to synthesize artificially, and small in size. LiNbO3The crystal growth process is mature, large-size crystals are easy to obtain, but the birefringence is too small. YVO4The crystal is an artificial birefringent crystal with excellent performance, but the ultraviolet transmittance is poor, so the application range is limited, and the problem also exists in calcite and rutile, α -BaB2O4The crystal is a new birefringent crystal recently reported to be useful in the ultraviolet region, but due to α -BaB2O4Solid phase transition exists, and the crystal quality is difficult to guarantee. Therefore, it is necessary to search for new crystal materials having a large birefringence and other excellent physical properties, particularly birefringent materials which can be used in the ultraviolet range.
Ca3(BO3)2Belongs to trigonal system, space group is R-3c, lattice constant a is 8.640(1) Å, c is 11.854(1) Å, Z is 6, V is 766.33(1) Å3. FIG. 1 is a structural diagram thereof, from which it can be seen that (BO) is in a crystal structure3)3-The radicals are plane triangular and different (BO)3)3-The plane triangles are parallel to each other and perpendicular to the optical axis direction, and we analyze that: under the action of the photoelectric field, the direction perpendicular to the plane of the group is easy to polarize (i.e. the charge is easy to distort), and the direction parallel to the group is less easy to polarize. Such anisotropy of polarization may cause Ca3(BO3)2The crystal has a large birefringence effect. While Ca is currently involved3(BO3)2The growth of crystals has not been reported.
Disclosure of Invention
The invention aims to provide Ca with high growth speed, low cost, easy obtainment of large size and high quality3(BO3)2A method for growing a single crystal by melt pulling.
The purpose of the invention is realized by the following technical scheme:
the invention provides a melt pulling growth method of calcium borate single crystal, which comprises the following steps:
1) preparation of Ca3(BO3)2Powder phase: mixing CaCO3And B2O3Powder mixingUniformly mixing, heating at 1200 ℃ for 24-36 hours, and slowly cooling to room temperature to obtain loose white feather-shaped pure Ca3(BO3)2Powder phase, the chemical equation of the process is as follows:
2) growth of Ca by melt Czochralski method3(BO3)2Single crystal:
ca prepared in the step 1)3(BO3)2Placing the powder in a platinum crucible, heating to 1500-1550 ℃ in a pull-up type single crystal furnace, keeping the temperature for 1-5 hours, then cooling to 1465-1480 ℃, after temperature balance, adopting directional seed crystals, discharging the seed crystals, and keeping the temperature for 1-2 hours; slowly cooling at a cooling speed of 0.5-3 ℃/h, starting crystal growth, rotating the crystal at a speed of 20-60 rpm, and pulling the crystal at a speed of 1-3 mm/h; and when the crystal grows to the required size, lifting the crystal out of the liquid level, and cooling to room temperature at the speed of 50-60 ℃/h to obtain the calcium borate single crystal.
The pull-up type single crystal furnace in the step 2) adopts a silicon-molybdenum rod as a heating element, a furnace shell water cooling device is provided, and a Pt/Pt-10% Rh type thermocouple is adopted.
In the step 2), a DWT-702 precise temperature controller and a Eurotherm818 temperature program controller are adopted as program control devices for carrying out temperature rise and fall and constant temperature in the crystal growth process.
The powder phase prepared in step 1) was analyzed by powder X-ray diffraction experiments with standard Ca3(BO3)2The powder diffraction cards were consistent.
Ca grown by the present invention3(BO3)2And (5) crystals, wherein each structural parameter is consistent with the data reported by the data through crystal structure determination. The grown crystals were colorless and transparent, had a Mohs hardness of about 4, and were slightly deliquescent in air. Rocking curve of X-rayThe half-peak width of the line is about 0.1 degree, and the crystal integrity is better.
Ca grown by the present invention3(BO3)2The crystal is a mixture of a crystal and a metal,the light transmission range is 180-3800 nm. At a wavelength of 589.3nm, the birefringence was about 0.097. Therefore, the material can be used for polarizing prisms in ultraviolet-infrared bands, electro-optical modulation devices and optical communication elements such as optical isolators, circulators, beam shifters and the like.
The invention uses a melt pulling method to grow Ca3(BO3)2The crystal can obtain large-size high-quality single crystal, and the process is simple, easy to operate, high in growth speed and low in cost.
Drawings
FIG. 1 is Ca3(BO3)2Structure of crystal.
Detailed Description
Example 1 preparation of Ca3(BO3)2Powder phase
Ca3(BO3)2The compound is synthesized at high temperature (1200 ℃) by adopting a solid phase sintering method, and the chemical reaction equation is as follows:
the specific operation steps are that 100.09g of CaCO is accurately weighed in an operation box according to the molar ratio of 3: 13And 23.21gB2O3Grinding them in mortar and mixing them thoroughly, then placing the ground material in platinum crucible with phi 70mm x 50mm, placing it in muffle furnace, slowly heating to 400 deg.C and holding constant temperature for 2 hr, then heating to 1200 deg.C and holding constant temperature for 48 hr, cooling to room temperature and taking out the crucible to obtain loose white feather sheet-like pure Ca3(BO3)2A powder phase.
The purity and the manufacturer of the used chemical reagent are as follows:
B2O3ar Beijing chemical Co Ltd
CaCO3Ar Beijing chemical reagentDriver
The prepared powder phase was analyzed by powder X-ray diffraction experiments with standard Ca3(BO3)2The powder diffraction cards were consistent.
Example 2 growth of Ca Using melt Czochralski method3(BO3)2Single crystal
300gCa to be accurately weighed3(BO3)2The raw materials are placed in a platinum crucible with the diameter of 40mm multiplied by 60mm, then the raw materials are placed in a self-made silicon-molybdenum rod growth furnace, a Pt/Pt-10% Rh type thermocouple is adopted, and a DWT-702 precise temperature control instrument and a Eurotherm818 temperature program control instrument are adopted as program control devices for carrying out temperature rise and fall and constant temperature in the crystal growth process. Heating to 1550 deg.C to melt the raw materials, keeping the temperature for 1 hr to mix the raw materials uniformly, and then rapidly cooling to 1465 deg.C. After the temperature is balanced, c-direction seed crystal is adopted, seed crystal is placed, the temperature is kept for 1h, and then the temperature is reduced to the temperature of a saturation point. After the temperature is balanced, the temperature is slowly reduced at the speed of 3 ℃/h, the crystal starts to grow, meanwhile, the crystal rotates at a certain speed of 60 rpm, and the crystal is pulled at the speed of 3 mm/h. When the crystal grows to the required size, the crystal is lifted from the liquid level and is cooled to the room temperature at the speed of 50 ℃/h, and the calcium borate single crystal 1 with the diameter of phi 25mm multiplied by 20mm is obtained.
Example 3
190gCa to be accurately weighed3(BO3)2The raw materials are placed in a platinum crucible with the diameter of 40mm multiplied by 60mm, then the raw materials are placed in a self-made silicon-molybdenum rod growth furnace, a Pt/Pt-10% Rh type thermocouple is adopted, and a DWT-702 precise temperature control instrument and a Eurotherm818 temperature program control instrument are adopted as program control devices for carrying out temperature rise and fall and constant temperature in the crystal growth process. Heating to 1500 deg.C to melt the raw materials, keeping the temperature for 5 hr to mix the raw materials uniformly, and then rapidly cooling to 1480 deg.C. After the temperature is balanced, c-direction seed crystal is adopted, seed crystal is placed, the temperature is kept for 2 hours, and then the temperature is reduced to the temperature of the saturation point. After the temperature is balanced, the temperature is slowly reduced at the speed of 0.5 ℃/h, the crystal starts to grow, and simultaneously the crystal rotates at a certain speed of 20 rpm and is pulled at the speed of 1 mm/h. When the crystal grows to the required size, the crystal is lifted from the liquid level and is reduced at the speed of 60 ℃/hAnd cooling to room temperature to obtain calcium borate single crystal 2 with the diameter of phi 30mm multiplied by 10 mm.
Example 4
190gCa to be accurately weighed3(BO3)2The raw materials are placed in a platinum crucible with the diameter of 40mm multiplied by 60mm, then the raw materials are placed in a self-made silicon-molybdenum rod growth furnace, a Pt/Pt-10% Rh type thermocouple is adopted, and a DWT-702 precise temperature control instrument and a Eurotherm818 temperature program control instrument are adopted as program control devices for carrying out temperature rise and fall and constant temperature in the crystal growth process. Heating to 1520 deg.C to melt the raw materials, keeping the temperature for 3 hr to mix the raw materials uniformly, and rapidly cooling to 1470 deg.C. After the temperature is balanced, c-direction seed crystal is adopted, seed crystal is placed, the temperature is kept for 1.5 hours, and then the temperature is reduced to the temperature of the saturation point. After the temperature is balanced, the temperature is slowly reduced at the speed of 1.5 ℃/h, the crystal starts to grow, and simultaneously, the crystal rotates at a certain speed of 40 rpm and is pulled at the speed of 2 mm/h. When the crystal grows to the required size, the crystal is lifted from the liquid level and is cooled to the room temperature at the speed of 55 ℃/h, and the calcium borate single crystal 3 with the diameter of phi 30mm multiplied by 10mm is obtained.
Ca grown in examples 2 to 4 of the present invention3(BO3)2The crystals 1-3 were subjected to crystal structure determination, and each structural parameter was consistent with the data reported in the data. The grown crystals were colorless and transparent, had a Mohs hardness of about 4, and were slightly deliquescent in air. The half-peak width of the X-ray rocking curve is about 12 arc seconds, and the crystal integrity is better.
Ca grown by the present invention3(BO3)2The light transmission range of the crystals 1-3 is 180-3800 nm. At a wavelength of 589.3nm, the birefringence was about 0.097. Therefore, the material can be used for polarizing prisms in ultraviolet-infrared bands, electro-optical modulation devices and optical communication elements such as optical isolators, circulators, beam shifters and the like.
Claims (3)
1. A melt pulling growth method of calcium borate single crystal comprises the following steps:
1) preparation of Ca3(BO3)2Powder phase: mixing CaCO3And B2O3Uniformly mixing the powder, heating at 1200 ℃ for 24-36 hours, and slowly cooling to room temperature to obtain pure Ca3(BO3)2A powder phase;
2) growth of Ca by melt Czochralski method3(BO3)2Single crystal:
ca prepared in the step 1)3(BO3)2Placing the powder in a platinum crucible, heating to 1500-1550 ℃ in a pull-up type single crystal furnace, keeping the temperature for 1-5 hours, then cooling to 1465-1480 ℃, after temperature balance, adopting directional seed crystals, discharging the seed crystals, and keeping the temperature for 1-2 hours; slowly cooling at a cooling speed of 0.5-3 ℃/h, starting crystal growth, rotating the crystal at a speed of 20-60 rpm, and pulling the crystal at a speed of 1-3 mm/h; and when the crystal grows to the required size, lifting the crystal out of the liquid level, and cooling to room temperature at the speed of 50-60 ℃/h to obtain the calcium borate single crystal.
2. The method for melt-pulling a calcium borate single crystal according to claim 1, wherein: the pull-up type single crystal furnace in the step 2) adopts a silicon-molybdenum rod as a heating element, a furnace shell water cooling device is provided, and a Pt/Pt-10% Rh type thermocouple is adopted.
3. The method for melt-pulling a calcium borate single crystal according to claim 1, wherein: in the step 2), a DWT-702 precise temperature controller and a Eurotherm818 temperature program controller are adopted as program control devices for carrying out temperature rise and fall and constant temperature in the crystal growth process.
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| CN 03157326 CN1252323C (en) | 2003-09-18 | 2003-09-18 | Process for growing calcium borate mono crystal by melt drawing |
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