CN108060456A - The Bridgman-Stockbarger method of beryllium aluminate crystal - Google Patents

Abstract

The invention belongs to technical field of single crystal growth, disclose a kind of method using Bridgman-Stockbarge method for growing beryllium aluminate crystal.By raw material A l₂O₃With BeO according to stoichiometric ratio weighing, it is uniformly mixed, briquetting；When pre-sintering 8~12 is small under 1200~1350 DEG C of furnace temperature, through solid state reaction kinetics beryllium aluminate polycrystalline component.The beryllium aluminate seed crystal for being orientated definite is placed in the seed slot of crucible bottom, synthetic polycrystalline component is reloaded into, screws crucible cover, then crucible is placed in descent method crystal growing furnace；It vacuumizes, treats that vacuum degree reaches 1 × 10^‑3During Pa, high-purity Ar is filled with as protective atmosphere；Heating is melted at 1870~1950 DEG C at the top of polycrystal raw material and seed crystal, and the control of growth interface temperature gradient is controlled in 10~40 DEG C/cm, dropping speed of the crucible in 0.5~10mm/h.The shape of beryllium aluminate crystal and size are easy to control in the present invention, avoid pollution of the volatilization to environment of beryllium oxide in melt, and more crucibles can be used and grow beryllium aluminate crystal simultaneously, and growth efficiency is high, is conducive to industrialized production.

Description

Growth method of beryllium aluminate crystal by crucible drop method

technical field

The invention relates to a method for growing beryllium aluminate crystals by using a crucible drop method, and belongs to the technical field of crystal growth.

Background technique

Beryllium aluminate crystal (chemical formula BeAl ₂ O ₄ ), melting point 1870°C, belongs to orthorhombic crystal system, lattice constant BeAl ₂ O ₄ crystal is an excellent laser host crystal material. Laser matrix crystal materials are the core and foundation of laser technology development, and play a pivotal role in all key stages of laser technology development. At present, yttrium aluminum garnet (YAG), yttrium vanadate (YVO ₄ ), and sapphire (Al ₂ O ₃ ) are still the most famous laser host crystals. BeAl ₂ O ₄ crystal is a laser host crystal material with great potential. As a host, its physical and chemical properties exceed that of YAG crystal, and the laser properties of chromium-doped beryllium aluminate (Cr:BeAl ₂ O ₄ ) laser crystal exceed that of ruby (Cr:Al ₂ O ₃ ) laser crystals, but the application range of BeAl ₂ O ₄ crystals is far less extensive than that of YAG crystals. This is mainly due to: (1) The growth of BeAl ₂ O ₄ crystals is difficult and requires more stringent process conditions. Because the melt of BeAl ₂ O ₄ crystal has a high viscosity, it is easy to cause cracks during the growth process, and the obtained crystal is prone to a series of defects such as scattering points, color bands, growth stripes, and uneven distribution of dopant ion concentration. Seriously affect the laser performance of the crystal; (2) When growing BeAl ₂ O ₄ crystal, due to the highly toxic Be element in the raw material, BeO volatilizes into the environment during the crystal growth process, which will harm the body and The environment causes great harm, so this product with great market and economic benefits has not been commercially developed.

Chinese patents (authorization number CN1062318C and authorization number CN101407402B) have successfully grown gem-level doped BeAl ₂ O ₄ crystals by using the rotating temperature gradient method and the vertical static temperature gradient method respectively, but the crystal quality is not up to the laser crystal standard, which makes the crystal limited. applications in lasers. The Chinese patent (publication number CN1824847A) adopts the variable speed crucible rotation pulling method to grow Cr:BeAl ₂ O ₄ crystals, and the use of variable speed crucible rotation can improve the uniformity of crystal melt components, but the grown Cr:BeAl ₂ O ₄ crystals Defects such as inclusions in the crystal growth process still cannot be completely solved, and the technical problem of volatilization of BeO in the melt cannot be solved by the pulling method. The Russian patent (RU2315134C1) uses the Kyropoulos method to grow beryllium aluminate crystals, but this method has a long period and is not conducive to industrial production.

The traditional crucible drop method for growing crystals (such as authorization number CN101280456B and authorization number CN10138940B) does not use a closed crucible, which cannot solve the problem that highly toxic volatiles volatilize and cause harm to the human body and the environment.

Contents of the invention

The object of the present invention is to overcome above-mentioned deficiencies in the prior art, propose a kind of BeAl ₂ O ₄ crucible descending method growth method of crystal, tighten the crucible cover to seal the crucible, can suppress the volatilization of BeO in the melt, make the melt more uniform, The obtained crystal laser has excellent performance; it also prevents the BeO in the melt from volatilizing out of the crucible to cause harm to the human body and the environment. Moreover, one or more BeAl ₂ O ₄ crystals with different specifications, shapes and crystallographic directions can be grown simultaneously, which improves the crystal growth efficiency.

Technical solution of the present invention is as follows:

The crucible drop method growth method of beryllium aluminate crystal is characterized in that: the method comprises the following steps:

① The initial raw materials Al ₂ O ₃ and BeO are weighed according to the stoichiometric ratio Al ₂ O ₃ : BeO=1:1, mixed evenly and compacted into a powder block;

②The powder block is pre-sintered at a furnace temperature of 1200-1350°C for 8-12 hours, and the polycrystalline beryllium aluminate component is synthesized through a solid-state reaction;

③ put the beryllium aluminate seed crystal with fixed orientation into the seed crystal groove at the bottom of the crucible, then put the beryllium aluminate polycrystalline component synthesized in step ② into the crucible, and tighten the crucible lid to seal the crucible;

④ Put the crucible in the descending method growth furnace, evacuate it, and fill it with high-purity Ar as a protective atmosphere when the vacuum degree reaches at least 1×10 ^-3 Pa;

⑤Raise the temperature to control the furnace temperature at 1870-1950°C, control the temperature gradient of the growth interface at 10-40°C/cm for inoculation and growth, and control the falling speed of the crucible at 0.5-10mm/h.

Further, the said beryllium aluminate crystals include beryllium aluminate matrix crystals and doped beryllium aluminate (eg doped with Cr ³⁺ , Ti ^{4 +} , V ⁵⁺ , Fe ³⁺ plasma) crystals.

Further, one of the raw materials, BeO, can be replaced by Be(OH) ₂ or BeCO ₃ , and the dopant ions (Cr ^{3 +} , Ti ⁴⁺ , V ⁵⁺ , Fe ^{3+ ,} etc.) can be these ions Oxides (such as Cr ₂ O ₃ , Ti ₂ O ₃ , V ₂ O ₅ , Fe ₂ O _{3 ,} etc.) or carbonates and hydroxides, etc., and the purity of all raw materials is greater than 99.9%.

Further, the crucible may be iridium crucible, molybdenum crucible, tungsten crucible, etc., and the crucible is equipped with a crucible cover.

Further, the crucible can be single hole or porous structure, the shape of the crucible can be cylindrical, square column or other polygonal shape, the shape of the grown crystal depends on the shape of the crucible, one beryllium aluminate crystal can be grown at a time or can be grown at the same time Beryllium aluminate crystals of different shapes and sizes are grown.

Further, the beryllium aluminate seed crystals with a certain orientation can be <001>, <010> or/and <100> orientation seeds, and beryllium aluminate crystals with different orientations can be grown in the same furnace.

Compared with the prior art, the present invention has the beneficial effects:

Compared with the temperature gradient method, the present invention has the same power and more stable temperature field during the crystal growth process, can effectively control component volatilization, has good crystal integrity, high yield, easier control of crystal size and shape, and solid-liquid interface temperature gradient. Small can reduce crystal cracking and so on. In addition, the method has simple process equipment, convenient operation and low energy consumption, all of which are beneficial to industrial production. Compared with the temperature gradient method and the Kyropoulos method for growing BeAl ₂ O ₄ crystals, the advantages of the present invention are listed in Table 1.

Table 1 The comparison between the present invention and the temperature gradient method and the Kyropoulos method of growing BeAl ₂ O ₄ crystals

Detailed ways

The present invention will be further described below in conjunction with embodiment, but should not limit protection scope of the present invention with this.

Example 1: Al ₂ O ₃ and BeO with a purity of 99.9% were weighed according to the stoichiometric ratio Al ₂ O ₃ : BeO=1:1, mixed evenly, compacted, and solid-state reacted at 1200°C for 12 hours to synthesize a polycrystalline group Then select the BeAl ₂ O ₄ seed crystal with orientation <001> and place it in the seed crystal tank at the bottom of the cylindrical molybdenum crucible, then put the synthesized polycrystalline components into the crucible, tighten the crucible lid to seal the crucible; place the crucible In the descending method crystal growth furnace, vacuumize, and when the vacuum degree reaches 1×10 ^-3 Pa, fill high-purity Ar as a protective atmosphere; heat up to 1900°C to melt the raw materials in the crucible, and adjust the position of the crucible into the furnace to make the seeds The top of the crystal is melted, the temperature gradient of the growth interface is controlled at about 40°C/cm, and the crucible is lowered at a speed of 1mm/h for crystal growth. Complete cylindrical BeAl ₂ O ₄ crystals with good internal quality can be obtained.

Example 2: Al ₂ O ₃ , BeO and Cr ₂ O ₃ with a purity of 99.9% were weighed according to the stoichiometric ratio, mixed uniformly, and compacted. The amount of dopant Cr ₂ O ₃ and BeO and Al ₂ O ₃ is calculated according to the following reaction equation:

(1-x)Al ₂ O ₃ +xCr ₂ O ₃ +BeO→BeAl _2-x Cr _x O ₄ (where x is the molar concentration of Cr ₂ O ₃ doped)

The polycrystalline components were synthesized by solid-state reaction at 1350°C for 8 hours; then the BeAl ₂ O ₄ seed crystal with the selected orientation <001> was placed in the seed crystal tank at the bottom of the rectangular cylindrical tungsten crucible, and the synthesized Put the polycrystalline components into the crucible, tighten the crucible lid to seal the crucible; place the crucible in a down-flow method crystal growth furnace, vacuumize it, and fill it with high-purity Ar as a protective atmosphere when the vacuum degree reaches 1×10 ^-3 Pa; Raise the temperature to 1950°C to melt the raw materials in the crucible and melt the top of the seed crystal by adjusting the position of the crucible into the furnace. The temperature gradient of the growth interface is controlled at about 20°C/cm, and the crucible is lowered at a speed of 10mm/h for crystal growth. A complete rectangular columnar BeAl _2-x Cr _x O ₄ laser crystal doped with Cr elements in the <001> direction can be obtained with good internal quality.

Example 3: Al ₂ O ₃ , BeO and Ti ₂ O ₃ with a purity of 99.9% were weighed according to the stoichiometric ratio, mixed uniformly, and compacted. The amount of dopant _Ti2O3 , BeO and _Al2O3 is _calculated according to the following reaction _equation :

(1-x)Al ₂ O ₃ +xTi ₂ O ₃ +BeO→BeAl _2-x Ti _x O ₄ (where x is the molar concentration of Ti ₂ O ₃ doped)

The agglomerate was subjected to solid-state reaction at 1300°C for 10 hours to synthesize polycrystalline components; then two BeAl ₂ O ₄ seed crystals with orientation <010> and <001> were selected and placed in the seed crystal tank at the bottom of the molybdenum crucible respectively , the crucible adopts a four-hole structure, two of which are cylindrical, and the other two are rectangular columns, and then the synthesized polycrystalline components are put into the crucible, and the crucible lid is tightened to seal the crucible; the crucible is placed in the descending method of crystal growth Vacuumize the furnace, and when the vacuum reaches 1×10 ^-3 Pa, fill it with high-purity Ar as a protective atmosphere; heat up to 1910°C to melt the raw materials in the crucible, and adjust the position of the crucible into the furnace to melt the top of the seed crystal and grow The interface temperature gradient is controlled at about 15°C/cm, and the crucible is lowered at a speed of 5 mm/h for crystal growth. Two rectangular columns and two complete columns of Ti-doped BeAl _2-x Ti _x O ₄ laser crystals with excellent internal quality can be obtained at the same time.

Finally, it should be noted that the above descriptions are only examples of the present invention, and are not intended to limit the scope of rights of the present invention. Apparently, any associated modifications or alterations to the embodiments made by those skilled in the art will not go beyond the concept of the present invention and the scope of protection of the appended claims.

Claims (7)

1. the Bridgman-Stockbarger method of beryllium aluminate crystal, it is characterised in that：This method comprises the following steps：

1. initial feed Al₂O₃With BeO according to stoichiometric ratio Al₂O₃：BeO=1:1 weighing is uniformly mixed and presses and forms powder agglomates；

2. the powder agglomates under 1200~1350 DEG C of furnace temperature pre-sintering 8~12 it is small when, through solid state reaction kinetics beryllium aluminate polycrystalline Component；

3. the beryllium aluminate seed crystal of fixed orientation is put into crucible bottom seed slot, the beryllium aluminate polycrystalline group for then 2. synthesizing step Divide and be put into crucible, and screw crucible cover sealed crucible；

It 4. crucible is placed in descent method for growing stove, vacuumizes, treats that vacuum degree reaches at least 1 × 10^-3During Pa, high-purity Ar work is filled with For protective atmosphere；

5. heating make Control for Kiln Temperature at 1870~1950 DEG C, inoculation, growth, growth interface temperature gradient control 10~40 DEG C/ Cm, dropping speed of the crucible are controlled in 0.5~10mm/h.

2. the Bridgman-Stockbarger method of beryllium aluminate crystal according to claim 1, it is characterised in that：The aluminic acid Beryllium crystal is beryllium aluminate host crystal or admixture beryllium aluminate crystal.

3. the Bridgman-Stockbarger method of beryllium aluminate crystal according to claim 2, it is characterised in that：The admixture Beryllium aluminate crystal is incorporation Cr³⁺、Ti⁴⁺、V⁵⁺Or Fe³⁺The beryllium aluminate crystal of ion.

4. the Bridgman-Stockbarger method of beryllium aluminate crystal described in claim 1, it is characterised in that：The initial feed BeO can use Be (OH)₂Or BeCO₃Substitution, the Doped ions Cr³⁺、Ti⁴⁺、V⁵⁺Or Fe³⁺It is the oxide of these ions Cr₂O₃、Ti₂O₃、V₂O₅Or Fe₂O₃Or the carbonate or hydroxide of these ions, the purity of the initial feed are equal More than 99.9%.

5. the Bridgman-Stockbarger method of beryllium aluminate crystal described in claim 1, it is characterised in that：The crucible is iraurite Crucible, molybdenum crucible or tungsten crucible, the crucible are furnished with crucible cover.

6. the Bridgman-Stockbarger method of the beryllium aluminate crystal described in claim 1 or 5, it is characterised in that：The crucible is Single hole or porous structure, crucible shape are cylindrical, square column type or other polygons, and the crystal shape of growth depends on crucible Shape, can piece beryllium aluminate crystal of a secondary growth or once simultaneously grow different shape, various sizes of beryllium aluminate crystal.

7. the Bridgman-Stockbarger method of beryllium aluminate crystal described in claim 1, it is characterised in that：The definite direction Beryllium aluminate seed crystal be<001>、<010>Or/and<100>Direction seed crystal, and the aluminium of different directions can be grown in same stove Sour beryllium crystal.