CN103114327B - A kind of molten-salt growth method eliminating low-temperature phase defection barium borate crystal core parcel - Google Patents
A kind of molten-salt growth method eliminating low-temperature phase defection barium borate crystal core parcel Download PDFInfo
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Abstract
The present invention relates to a kind of molten-salt growth method eliminating low-temperature phase defection barium borate crystal core parcel, it is specifically related to the vibration by crystal to be carried out low frequency and short arc in crystal growing process in vertical seed crystal direction, the thickness of the interface diffusion layer between reduction crystal and melt, improve the bottom solute transport ability that seed crystal extends, eliminate the parcel at position, germ nucleus (bottom seed crystal), prepare the crystal of coreless.
Description
Technical field
The artificial crystal growth field that the present invention relates to, particularly to a kind of molten-salt growth method eliminating low-temperature phase defection barium borate crystal core parcel.
Background technology
Nonlinear optical crystal (nonlinearopticalcrystal) is the functional crystal that a class is important, can be used for making the components and parts such as frequency multiplication, mixing, Electro-optical Modulation, optical parametric oscillator and optical waveguide, defined fairly large industrial market in the world. In numerous nonlinear optical crystals, have been carried out commercial crystal and few, mainly have three kinds, i.e. ��-BBO(low-temperature phase barium metaborate), LBO(tri-Lithium biborate) and KTP(potassium titanium oxide phosphate).
��-bbocrystal is the nonlinear optical crystal being widely used and being described as " China card " at present, it has very big effective Clock Multiplier Factor (6 times for KDP crystal), very wide transparent wave band district (190-3500nm), low dispersion, bigger birefringence and significantly high photodamage resistant value; And there is good mechanical performance, it is easy to cutting, polishing, plated film, be slightly soluble in water, but not deliquescence under experiment condition. ��-bbocrystal is widely used in the secondary of Nd:YAG laser, three times, four times and quintuple harmonics generation (can obtain the coherent radiation of 532nm, 355nm, 266nm, 213nm respectively), the secondary of dye laser and triple-frequency harmonics, Ti:Al2O3The secondary of laser and Alexandrite laser, three times, four-time harmonic, the aspect such as frequency multiplication of optical parametric oscillator (OPO) and optical parametric amplifier (OPA), argon ion, copper laser and ruby laser.
There is 2 kinds of phases, i.e. high-temperature-phase and low-temperature phase in bbo crystal, wherein low-temperature phase has nonlinear effect. The fusing point of BBO is 1095 DEG C, and the phase transition temperature of high/low temperature phase is 920 DEG C, so cosolvent must be added, adopts high-temperature molten salt method to carry out ��-bbocrystal growth. Major Epidemic in high-temperature molten salt method is seed-grain method, and the method can the bigger crystal of growth quality higher dimensional. Modal in seed-grain method is again top-seeded solution growth. It easily observes in growth course, and the speed of growth is also very fast simultaneously, because the existing diffusion of quality transport therein has again convection current crystal, this plays an effect stirring melt in the process rotated.
Owing to wrapping up below the existence, particularly seed crystal of defect and expanding the parcel defect of shoulder surface portion so that the utilization rate of bulk crystal blank is very low.In recent years, along with electro-optical Q-switch application is more and more higher to the dimensional requirement of large scale ��-bbocrystal device, how to eliminate the parcel defect below seed crystal and have become as the focus of ��-bbocrystal Study on Preparation Technology.
All kinds of document of early stage all shows, the wrappage of the central area in ��-bbocrystal blank is mainly caused by supercool growth, and namely transporting of solute lags behind the speed of growth. In ��-bbocrystal growth course, by with seed crystal for rotating shaft rotating crystal, strengthening the solute transport between crystal and melt. In crystal edge position, owing to crystal is relatively big with the rotating speed of melt pair, the impurity of crystal growth interface is easy to be rejected in melt, and below seed crystal, its melt is essentially in resting state. The impurity at this place cannot be rejected in melt smoothly, just as wrappage, enters in crystal.
The concept of fluid boundary layer is put forward in 1904 by Prandtl, it has also become one of contemporary fluid dynamic foundation stone. In recent years, scientists introduces boundary region concept in ��-bbocrystal growth model and carries out theory analysis. Owing to introducing boundary region concept, crystal to melt can be divided into three parts, namely crystal, boundary region, melt, in the melt, transporting mainly by convection current of solute (particularly impurity), the efficiency transported is very high; And in boundary region, solute transport is mainly by diffusion, the efficiency transported is much lower. Meanwhile, theoretical research shows, under the premise that other condition is constant, in boundary region, the efficiency of solute transport and the thickness of boundary region are inverse ratio. The experiment of early stage crystal growth again shows that, reduces boundary layer thickness, it is possible to be effectively improved the eliminating of impurity, and probability that wrappage defect occur is greatly lowered.
By suitably strengthening crystal rotation, it is possible to effectively reduce boundary layer thickness. But being as the increase of crystal diameter and rotating speed, solution changes from free convection to forced convection, thus changing the Temperature Distribution of growth interface, namely changes degree of supersaturation, ultimately result in the shape at interface from Raised key axis through the planar interface transformation to recessed interface. When rotating speed exceedes certain limit (experiments show that of early stage, when rotating speed is more than 10r/min) time, too high rotating speed is by destroying the stability at interface and forming countless groove on interface, to cause interface to entirely collapse so that whole crystal is all the tiny wrappage of disperse. The invention provides a kind of new molten-salt growth method, under the premise not increasing crystal rotation, effectively reduce boundary layer thickness, promote transporting of solute, grown large scale high-quality ��-bbocrystal.
Summary of the invention
For overcoming the shortcoming easily producing core parcel in tradition molten-salt growth method, the present invention by carrying out the vibration of low frequency and short arc in crystal growing process by crystal in vertical seed crystal direction, the thickness of the interface diffusion layer between reduction crystal and melt, improve the bottom solute transport ability that seed crystal extends, eliminate the parcel bottom the both seed crystals of position, germ nucleus, prepare the crystal of coreless.
Technical scheme is as follows:
1. crystal growing apparatus:
Crystal growing apparatus of the present invention is top-seeded solution growth crystal growing furnace. This growth furnace possesses and rotates clockwise and the upper and lower two-way function quickly and at a slow speed lifted, and its seed rod can make the low frequency up and down of vertical direction and the periodic vibration of short arc. Because the temperature of growth is lower than 1000 �� of C, growth furnace of the present invention is to use Aludirome heater strip as calandria, filling resistant to elevated temperatures aluminium oxide heat-preservation cotton between burner hearth and furnace shell, temperature controls to adopt Pt/Pt-Rh thermocouple, and temperature control precision is at �� 0.10 �� of C;
2. crystal growth parameters:
Using diameter is the platinum crucible of 100mm, and crucible liquid level is 2��10 �� of C to the temperature difference of crucible bottom; Seed crystal direction is [001], and during crystal growth, seed rod slewing rate is 5 ~ 20r/min, and rate of temperature fall is 0��0.3 �� of C/h, and the frequency of vibration of seed rod is 0.01��1Hz, and amplitude is 0.01mm��0.1mm; During annealing, seed rod stops operating, and rate of temperature fall is 5��20 �� of C/h;
3. crystal growth step:
1) by BaCO weighted in advance3��H3BO3With flux by preset blending ratio, mix in Achates alms bowl and mill, be sufficiently mixed in the material crucible loading platinum material after uniformly;
2) material platinum crucible is put in Muffle furnace, be warmed up at the temperature of 1000 �� of C and fully react 2h; Then with Crucible tongs, crucible tongs are gone out, melt is poured in the growth crucible that diameter is 100mm of platinum material, until raw material is full of more than the 90% of growth crucible;
3) growth crucible is inserted in crystal growing furnace, slowly heat up after making raw material be completely melt, continue to heat up, constant temperature 24h at the temperature of the high 30 �� of C of fusing point, make liquation homogenization; Subsequently temperature is slowly dropped to the growth temperature estimated;
4) being fixed on crystalline style by fritter ��-bbocrystal to be slowly dropped to liquid level, made repeated attempts by trial and error method, measure the not molten not long temperature of seed crystal of sening as an envoy to, this temperature spot is saturation temperature point;
5) take out fritter ��-bbocrystal, melt temperature is raised 30 �� of C, constant temperature 24h, then slowly melt temperature is down to the temperature of high 1 �� of C than saturation temperature;
6) an axial high-quality ��-BBO seed crystal of edge [001] is fixed on crystalline style, lentamente the lower end of seed crystal is dropped to mouth of pot position, and keeps seed rod to rotate (10��30 turns/min), constant temperature 12h;
7) seed crystal is dropped to just contact liquid level subsequently, control temperature than growth temperature high 1 �� of C, then by a little for seed crystal face fusing, eliminate the manufacturing deficiency of seed crystal face;
8) after 2h, cool the temperature to saturation temperature, continue constant temperature 24h;
9) being lowered the temperature by auto-programming, start crystal growth, during growth, slewing rate is 5 ~ 20r/min, and rate of temperature fall is 0��0.3 �� of C/h, and seed rod carries out vibrating along seed crystal direction, and frequency of vibration is 0.01��1Hz, and amplitude is 0.01mm��0.1mm.
10) crystal growth can last till that melt temperature drops to 800 �� of C, it is also possible to stops carrying out crystal growth at the temperature spot higher for C than 800 ��;
11) the crystal speed of 1��5mm/h upwards being lifted, until lift-off melt, the cooling then carrying out melt processes, and rate of temperature fall is 5��20 �� of C/h.
In traditional molten salt growth top-seeded solution growth crystal growth, the effective ways that reinforcement interface diffusion layer impurity spreads in melt are to reduce the interface thickness of diffusion layer between crystal and melt, generally by improving the slewing rate of crystal or adopting rotating method alternately to realize. But there is certain limitation in both approaches, namely the limited efficiency that rotating speed increase changes very little, rotating speed increases too fast, certain limit is exceeded once rotating speed, too high rotating speed will destroy the stability at interface and forms countless groove on interface, to cause interface to entirely collapse, making whole crystal is all the tiny wrappage of disperse, it is characteristic of the invention that the vibration by crystal to be carried out low frequency and short arc in crystal growing process in vertical seed crystal direction, under the premise not increasing crystal rotation, effectively reduce boundary layer thickness, promote transporting of solute. Actual crystal growth experiment shows that this method is respond well, it is possible to increase substantially the bottom solute transport ability that seed crystal extends, and eliminates the parcel at position, germ nucleus (bottom seed crystal), prepares the ��-bbocrystal of coreless.
Detailed description of the invention:
Embodiment one: adopt NaF as flux, it is the most typical flux of growth ��-BBO, and the stable growth district of ��-BBO is very big, it is allowed to grow bigger ��-BBO monocrystalline. The molar ratio of flux NaF content is NaF is 34% to 60%.
Crystal growth step:
1) by BaCO weighted in advance3��H3BO3With NaF by preset blending ratio, mix in Achates alms bowl and mill, be sufficiently mixed in the material crucible loading platinum material after uniformly;
2) material platinum crucible is put in Muffle furnace, be warmed up at the temperature of 1000 �� of C and fully react 2h; Then with Crucible tongs, crucible tongs are gone out, melt is poured in the growth crucible that diameter is 100mm of platinum material, until raw material is full of more than the 90% of growth crucible;
3) growth crucible is inserted in crystal growing furnace, slowly heat up after making raw material be completely melt, continue to heat up, constant temperature 24h at the temperature of the high 30 �� of C of fusing point, make liquation homogenization; Subsequently temperature is slowly dropped to the growth temperature estimated;
4) being fixed on crystalline style by fritter ��-bbocrystal to be slowly dropped to liquid level, made repeated attempts by trial and error method, measure the not molten not long temperature of seed crystal of sening as an envoy to, this temperature spot is saturation temperature point;
5) take out fritter ��-bbocrystal, melt temperature is raised 30 �� of C, constant temperature 24h, then slowly melt temperature is down to the temperature of high 1 �� of C than saturation temperature;
6) an axial high-quality ��-BBO seed crystal of edge [001] is fixed on crystalline style, lentamente the lower end of seed crystal is dropped to mouth of pot position, and keeps seed rod to rotate (10��30 turns/min), constant temperature 12h;
7) seed crystal is dropped to just contact liquid level subsequently, control temperature than growth temperature high 1 �� of C, then by a little for seed crystal face fusing, eliminate the manufacturing deficiency of seed crystal face;
8) after 2h, cool the temperature to saturation temperature, continue constant temperature 24h;
9) being lowered the temperature by auto-programming, start crystal growth, during growth, slewing rate is 5 ~ 20r/min, and rate of temperature fall is 0��0.3 �� of C/h, and seed rod carries out vibrating along seed crystal direction, and frequency of vibration is 0.01��1Hz, and amplitude is 0.01mm��0.1mm;
10) crystal growth can last till that melt temperature drops to 760 �� of C, it is also possible to stops carrying out crystal growth at the temperature spot higher for C than 760 ��;
11) the crystal speed of 1��5mm/h upwards being lifted, until lift-off melt, the cooling then carrying out melt processes, and rate of temperature fall is 5��20 �� of C/h.
Embodiment two:
Adopting NaCl as flux, it is the flux that growth ��-BBO is a kind novel, and the stable growth district of ��-BBO is very big, it is allowed to grow bigger ��-BBO monocrystalline. The molar ratio of flux NaCl content is NaCl is 25% to 43%.
Crystal growth step:
1) by BaCO weighted in advance3��H3BO3With NaCl by preset blending ratio, mix in Achates alms bowl and mill, be sufficiently mixed in the material crucible loading platinum material after uniformly;
Other step and in embodiment 1 2)��11) consistent.
Claims (3)
1. eliminating a molten-salt growth method for low-temperature phase defection barium borate crystal core parcel, crystal growth step is as follows:
By BaCO weighted in advance3��H3BO3With NaF by preset blending ratio, mix in Achates alms bowl and mill, be sufficiently mixed in the material crucible loading platinum material after uniformly;
Material platinum crucible is put in Muffle furnace, is warmed up at the temperature of 1000 �� of C and fully reacts 2h; Then with Crucible tongs, crucible tongs are gone out, melt is poured in the growth crucible that diameter is 100mm of platinum material, until raw material is full of more than the 90% of growth crucible;
Growth crucible is inserted in crystal growing furnace, slowly heat up after making raw material be completely melt, continue to heat up, constant temperature 24h at the temperature of the high 30 �� of C of fusing point, make liquation homogenization; Subsequently temperature is slowly dropped to the growth temperature estimated;
Being fixed on crystalline style by fritter ��-bbocrystal to be slowly dropped to liquid level, made repeated attempts by trial and error method, measure the not molten not long temperature of seed crystal of sening as an envoy to, this temperature spot is saturation temperature point;
Take out fritter ��-bbocrystal, melt temperature is raised 30 �� of C, constant temperature 24h, then slowly melt temperature is down to the temperature of high 1 �� of C than saturation temperature;
A piece axial high-quality ��-BBO seed crystal of edge [001] is fixed on crystalline style, lentamente the lower end of seed crystal is dropped to mouth of pot position, and keeps seed rod to rotate 10 ~ 30 turns/min, constant temperature 12h;
Being dropped to by seed crystal subsequently and just contact liquid level, control temperature is high 1 �� of C than growth temperature, then by a little for seed crystal face fusing, eliminates the manufacturing deficiency of seed crystal face;
After 2h, cool the temperature to saturation temperature, continue constant temperature 24h;
Being lowered the temperature by auto-programming, start crystal growth, during growth, slewing rate is 5 ~ 20r/min, rate of temperature fall is 0��0.3 �� of C/h, seed rod is made the low frequency up and down of vertical direction and the periodic vibration of short arc, and frequency of vibration is 0.01��1Hz, and amplitude is 0.01mm��0.1mm;
Crystal growth lasts till that melt temperature drops to 760 �� of C, stops carrying out crystal growth;
The crystal speed of 1��5mm/h upwards being lifted, until lift-off melt, the cooling then carrying out melt processes, and rate of temperature fall is 5��20 �� of C/h.
2. a kind of molten-salt growth method eliminating low-temperature phase defection barium borate crystal core parcel as claimed in claim 1, it is characterised in that: crucible liquid level is 2��10 �� of C to the temperature difference of crucible bottom; During crystal growth, seed rod slewing rate is 5 ~ 20r/min, and rate of temperature fall is 0��0.3 �� of C/h, and the frequency of vibration of seed rod is 0.01��1Hz, and amplitude is 0.01mm��0.1mm; During annealing, seed rod stops operating, and rate of temperature fall is 5��20 �� of C/h, and seed rod stops vibration.
3. a kind of molten-salt growth method eliminating low-temperature phase defection barium borate crystal core parcel as claimed in claim 1, it is characterised in that: growth system adopts " BBO-NaF " system, and wherein NaF is flux, and the molar ratio of its content is 25% to 60%.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101748476A (en) * | 2008-12-15 | 2010-06-23 | 福建福晶科技股份有限公司 | Special processing method for growing large-size high-quality BBO crystals |
| CN101748475A (en) * | 2008-12-15 | 2010-06-23 | 福建福晶科技股份有限公司 | Special processing method for growing large-size high-quality LBO crystals |
| CN101880908A (en) * | 2009-05-05 | 2010-11-10 | 福建福晶科技股份有限公司 | Method for preparing originated multi-section yttrium vanadate laser crystal |
| CN102383182A (en) * | 2011-10-23 | 2012-03-21 | 福建福晶科技股份有限公司 | Molten-salt growth method for reducing central envelope of BBO(Barium Boron Oxide) crystals |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101748476A (en) * | 2008-12-15 | 2010-06-23 | 福建福晶科技股份有限公司 | Special processing method for growing large-size high-quality BBO crystals |
| CN101748475A (en) * | 2008-12-15 | 2010-06-23 | 福建福晶科技股份有限公司 | Special processing method for growing large-size high-quality LBO crystals |
| CN101880908A (en) * | 2009-05-05 | 2010-11-10 | 福建福晶科技股份有限公司 | Method for preparing originated multi-section yttrium vanadate laser crystal |
| CN102383182A (en) * | 2011-10-23 | 2012-03-21 | 福建福晶科技股份有限公司 | Molten-salt growth method for reducing central envelope of BBO(Barium Boron Oxide) crystals |
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