WO2022077546A1 - 一种大尺寸钽酸锂晶体单畴化方法 - Google Patents

一种大尺寸钽酸锂晶体单畴化方法 Download PDF

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WO2022077546A1
WO2022077546A1 PCT/CN2020/123110 CN2020123110W WO2022077546A1 WO 2022077546 A1 WO2022077546 A1 WO 2022077546A1 CN 2020123110 W CN2020123110 W CN 2020123110W WO 2022077546 A1 WO2022077546 A1 WO 2022077546A1
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crystal
lithium tantalate
polarization
polarized
temperature
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PCT/CN2020/123110
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French (fr)
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张忠伟
徐秋峰
张鸿
陈晓强
张坚
顾建生
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天通控股股份有限公司
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Priority to KR1020227021975A priority Critical patent/KR20220134523A/ko
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    • 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
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • 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
    • C30B29/30—Niobates; Vanadates; Tantalates
    • 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
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • C30B33/02—Heat treatment

Definitions

  • the invention relates to the field of piezoelectric crystals, and in particular relates to a method for single domain formation of large-sized lithium tantalate crystals.
  • the crystal ends gradually tend to develop in the direction of large size.
  • the polarization medium of lithium tantalate crystals has high temperature shedding after size enlargement. The phenomenon that the monodomainization effect becomes worse; after the large-size lithium tantalate crystal is polarized by the original temperature process, the monodomainization effect is not complete, but after the polarization temperature is increased, the crystal has high temperature cracking phenomenon; these problems seriously affect the Piezoelectric properties and manufacturing costs of large-sized lithium tantalate crystals.
  • the existing Chinese patent document discloses a doped lithium niobate crystal polarization process and its device, patent number: 93110359.2, which mentions that the polarized end face of the crystal is polished and the polarized ceramic plate is polished.
  • the operation process is complicated, and the bonding degree is poor by the pressing block, and the temperature is used as the polarization point, which is easy to cause crystal cracking.
  • the purpose of the present invention is to provide a method for single domain formation of large-sized lithium tantalate crystals.
  • the present invention provides the following technical solutions:
  • a method for single domain formation of large-size lithium tantalate crystal comprising the following steps:
  • the polarizing medium is prepared by mixing lithium carbonate raw material powder and a binder into a slurry in a weight ratio of 1:0.8 to 1:1, and the binder is CMC glue.
  • the purity of lithium carbonate raw material is required to be 99.99%.
  • step b) the gold wire is buried in the middle of the polarized medium, the head and tail polarized crystal gold wire is wound into a circular spiral shape, the side polarized crystal gold is wound into a rectangular spiral shape, the diameter of the gold wire is 1mm, and the wiring spacing is required 3-5mm, the size is consistent with the size of the polarized medium.
  • step c) the best point of polarization of lithium tantalate crystal is confirmed by the resistance tester according to the resistance change, and the current size is automatically controlled by PLC adjustment, and the required value of the polarization current of lithium tantalate crystal is:
  • the current value is 1.2* ⁇ *R2 (1.2 is the crystal polarization coefficient, unit Ma/mm 2 , R is the crystal radius, unit mm), and the current value required for side polarization is 1.5*L*D (1.5 is the crystal polarization Coefficient, unit Ma/mm 2 , L is crystal height, unit mm, D is crystal diameter, unit mm).
  • a slurry for polarization is made by mixing lithium carbonate raw material powder and a binder.
  • the binder adopts CMC glue, which has the advantages of good viscosity, fast drying, no falling off at high temperature, and no reaction with crystals.
  • the medium adopts slurry design, which improves the firmness of the contact surface of the polarized medium and the fit of the contact surface of the polarized medium, which can effectively prevent the medium from falling off.
  • This process can reduce the influence of the high temperature environment on the conductivity of the gold wire and the problem of high temperature shedding of the gold wire by the wiring form of the gold wire buried in the polarizing medium, so that the control of the polarization current is more stable, thereby effectively reducing the
  • the cracking rate of large-sized lithium tantalate crystals improves the monodomain effect of crystals.
  • the optimal polarization point is determined by the resistance change rate through the resistance test method, and the polarization coefficients of the head-tail polarized crystal and the side-polarized crystal are distinguished, which can ensure the integrity of the crystal and achieve the Best polarization effect.
  • Fig. 1 is a schematic diagram of crystal polarization in Example 1; wherein, 1-polarization medium, 2-gold wire polarization electrode, 3-polarization circuit, 4-PLC polarization controller, 5-resistance tester, 6-tantalum Lithium oxide crystals.
  • FIG. 2 is a graph showing the relationship between the polarization temperature and the resistance of the lithium tantalate crystal in Example 1; wherein, the black dot at 650° C. is the polarization point.
  • a method for single domain formation of large-size lithium tantalate crystal comprising the following steps:
  • the bottom of the ceramic crucible for annealing is covered with lithium tantalate raw material powder, and the powder mesh number is required to be 20-30 mesh, and then the bottom of the lithium tantalate crystal is buried in the lithium tantalate raw material powder to fix, and placed in a high-temperature furnace, press 50- The temperature was raised to 1350°C at a heating rate of 60°C/h, kept for 4 hours, and then lowered to room temperature at a cooling rate of 50-60°C/h to complete crystal annealing.
  • the raw material powder of lithium carbonate and the binder in a weight ratio of 1:0.8 to 1:1, and use a mixer to stir evenly.
  • the stirring rate is 20rpm/min and the stirring time is 10min to prepare a slurry for polarization.
  • the crystal is cleaned with alcohol, and the polarization direction is confirmed according to the crystal axis.
  • the smearing position of the polarization medium of the head-tail polarization crystal is the upper and lower ends of the crystal, and the smearing range is ⁇ *R 2 (R is the crystal radius); side polarization
  • the smearing position of the polarizing medium of the crystal is the long axis of the crystal, and the size of the smearing range is L*2/3*D (L is the height of the crystal, D is the diameter of the crystal), and then the gold wire is buried in the middle of the polarizing medium, and the head and tail are polarized.
  • the crystal gold wire is wound into a circular spiral, and the side polarized crystal gold is wound into a rectangular spiral.
  • the wiring spacing is required to be 3-5mm, and the size is consistent with the size of the polarized medium. It is quickly dried to make polarized crystal caps.
  • the binder is CMC glue.
  • the lithium tantalate crystal to be polarized is fixed on the polarizing seat, the polarizing circuit is connected, and the temperature is increased at a heating rate of 50-60 °C/h.
  • the temperature exceeds the Curie temperature (600 °C)
  • use a resistance tester to connect the positive and negative ends of the polarized line to test the resistance, and record the resistance change of the lithium tantalate crystal.
  • the lithium tantalate crystal is polarized by applying a current at a rate of 5MA/min, and the current value required for the head and tail polarization is 1.2* ⁇ *R 2 (1.2 is the crystal polarization coefficient unit Ma/mm 2 , R is the crystal Radius unit mm), the current value required for side polarization is 1.5*L*D (1.5 is the crystal polarization coefficient unit Ma/mm 2 , L is the crystal height unit mm, D is the crystal diameter unit mm), to reach the required current value After that, stop the current application, keep the temperature for 4 hours, and lower the temperature by 50-60°C/h. When the temperature is lower than 600°C, turn off the polarization current and wait for the crystal to drop to room temperature.
  • the polarizing medium and the gold wire did not fall off, and the overall permeability of the crystal was found to be good when inspected with a laser pointer. Complete, evenly distributed, in the same direction.
  • a method for single domain formation of large-size lithium tantalate crystal comprising the following steps:
  • the bottom of the ceramic crucible for annealing is covered with lithium tantalate raw material powder, and the powder mesh number is required to be 20-30 mesh, and then the bottom of the lithium tantalate crystal is buried in the lithium tantalate raw material powder to fix, and placed in a high-temperature furnace, press 50- The temperature was raised to 1350°C at a heating rate of 60°C/h, kept for 4 hours, and then lowered to room temperature at a cooling rate of 50-60°C/h to complete crystal annealing.
  • Lithium carbonate is pressed into a polarizing medium with a thickness of 5mm, the annealed crystal is cleaned with alcohol, and the polarization direction is confirmed according to the crystal axis.
  • ⁇ *R 2 (R is the crystal radius); the fixed position of the side polarized crystal polarizing medium is the long axis of the crystal, and the range is L*2/3*D (L is the crystal height, D is the crystal diameter), and then the polar A gold sheet is fixed on the polarized medium to make a polarized crystal cap.
  • the lithium tantalate crystal to be polarized on the polarizing seat, connect the polarizing circuit, and heat up at a heating rate of 50-60 °C/h.
  • the temperature exceeds the Curie temperature (600 °C)
  • use a resistance tester to connect The resistance test is carried out on the positive and negative ends of the polarized line, and the resistance change of the lithium tantalate crystal is recorded.
  • the resistance change rate becomes smaller and reaches 2 ⁇ /10°C, the temperature rise is suspended, and the PLC is turned on to apply a current at a rate of 5Ma/min to the tantalum.
  • the lithium oxide crystal is polarized, and the current value required for the head and tail polarization is 1.2* ⁇ *R 2 (1.2 is the crystal polarization coefficient unit Ma/mm 2 , R is the crystal radius unit mm), and the side polarization requirements
  • the current value is 1.5*L*D (1.5 is the crystal polarization coefficient unit Ma/mm 2 , L is the crystal height unit mm, D is the crystal diameter unit mm), stop adding current after reaching the required current value, and keep it for 4h. Cool down at 50-60°C/h. When the temperature is lower than 600°C, turn off the polarization current and wait for the crystal to drop to room temperature.
  • the polarizing medium and the gold sheet have partially fallen off or moved in position.
  • the permeability of some areas of the crystal was poor, and the crystal slices were corroded and domainized before use.
  • the crystallographic microscope found that the domains in some regions of the crystal were not completely reversed, and the orientation consistency was poor.
  • a method for single domain formation of large-size lithium tantalate crystal comprising the following steps:
  • the bottom of the ceramic crucible for annealing is covered with lithium tantalate raw material powder, and the powder mesh number is required to be 20-30 mesh, and then the bottom of the lithium tantalate crystal is buried in the lithium tantalate raw material powder to fix, and placed in a high-temperature furnace, press 50- The temperature was raised to 1350°C at a heating rate of 60°C/h, kept for 4 hours, and then lowered to room temperature at a cooling rate of 50-60°C/h to complete crystal annealing.
  • the raw material powder of lithium carbonate and the binder in a weight ratio of 1:0.8 to 1:1, and use a mixer to stir evenly.
  • the stirring rate is 20rpm/min and the stirring time is 10min to prepare a slurry for polarization.
  • the crystal is cleaned with alcohol, and the polarization direction is confirmed according to the crystal axis.
  • the smearing position of the polarization medium of the head-tail polarization crystal is the upper and lower ends of the crystal, and the smearing range is ⁇ *R 2 (R is the crystal radius); the side polarization crystal
  • the smearing position of the polarizing medium is the long axis of the crystal, and the size of the smearing range is L*2/3*D (L is the height of the crystal, D is the diameter of the crystal), and then the gold wire is buried in the middle of the polarizing medium, and quickly dried to make a pole. Crystal cap.
  • the binder is CMC glue.
  • the lithium tantalate crystal to be polarized on the polarizing seat, connect the polarizing circuit, and heat up at a heating rate of 50-60 °C/h.
  • the temperature exceeds the Curie temperature (600 °C)
  • use a resistance tester to connect The resistance test is carried out on the positive and negative ends of the polarized line, and the resistance change of the lithium tantalate crystal is recorded.
  • the resistance change rate becomes smaller and reaches 2 ⁇ /10°C, the temperature rise is suspended, and the PLC is turned on to apply a current at a rate of 5Ma/min to the tantalum.
  • the lithium oxide crystal is polarized, and the current value required for the head and tail polarization is 1.2* ⁇ *R2 (1.2 is the crystal polarization coefficient unit Ma/mm2, R is the crystal radius unit mm), and the current required for the side polarization is The value is 1.5*L*D (1.5 is the crystal polarization coefficient unit Ma/mm2, L is the crystal height unit mm, D is the crystal diameter unit mm). Cool down at 60°C/h. When the temperature is lower than 600°C, turn off the polarization current and wait for the crystal to drop to room temperature.
  • the large-size lithium tantalate crystal produced in this comparative example was inspected with a laser pointer and found that the permeability of the crystal part was poor. After the crystal slice was corroded and domainized, it was found that the domain in part of the crystal was not completely reversed, and the direction consistency was relatively consistent. Difference. The reason for the analysis is that the gold wire is not evenly routed, resulting in uneven current distribution in some areas.
  • a method for single domain formation of large-size lithium tantalate crystal comprising the following steps:
  • the bottom of the ceramic crucible for annealing is covered with lithium tantalate raw material powder, and the powder mesh number is required to be 20-30 mesh, and then the bottom of the lithium tantalate crystal is buried in the lithium tantalate raw material powder to fix, and placed in a high-temperature furnace, press 50- The temperature was raised to 1350°C at a heating rate of 60°C/h, kept for 4 hours, and then lowered to room temperature at a cooling rate of 50-60°C/h to complete crystal annealing.
  • the raw material powder of lithium carbonate and the binder in a weight ratio of 1:0.8 to 1:1, and use a mixer to stir evenly.
  • the stirring rate is 20rpm/min and the stirring time is 10min to prepare a slurry for polarization.
  • the crystal is cleaned with alcohol, and the polarization direction is confirmed according to the crystal axis.
  • the smearing position of the polarization medium of the head-tail polarization crystal is the upper and lower ends of the crystal, and the smearing range is ⁇ *R 2 (R is the crystal radius); the side polarization crystal
  • the smearing position of the polarizing medium is the long axis of the crystal, and the size of the smearing range is L*2/3*D (L is the height of the crystal, D is the diameter of the crystal).
  • the side polarized crystal gold is wound into a rectangular spiral shape, the wiring spacing is required to be 3-5mm, and the size is consistent with the size of the polarized medium. It is quickly dried to make polarized crystal caps.
  • the binder is CMC glue.
  • the lithium tantalate crystal is polarized by applying a current at a rate, and the current value required for the head and tail polarization is 1.2* ⁇ *R 2 (1.2 is the crystal polarization coefficient unit Ma/mm2, R is the crystal radius unit mm), The current value required for side polarization is 1.5*L*D (1.5 is the crystal polarization coefficient unit Ma/mm 2 , L is the crystal height unit mm, D is the crystal diameter unit mm), stop adding current after reaching the required current value, After holding for 4h, cool down at 50-60°C/h. When the temperature is lower than 600°C, turn off the polarization current and wait for the crystal to drop to room temperature.
  • the large-size lithium tantalate crystals produced in this comparative example have internal cracking phenomenon, and it is judged that when the temperature is polarized, the temperature is too high to cause crystal cracking.
  • a method for single domain formation of large-size lithium tantalate crystal comprising the following steps:
  • the bottom of the ceramic crucible for annealing is covered with lithium tantalate raw material powder, and the powder mesh number is required to be 20-30 mesh, and then the bottom of the lithium tantalate crystal is buried in the lithium tantalate raw material powder to fix, and placed in a high-temperature furnace, press 50- The temperature was raised to 1350°C at a heating rate of 60°C/h, kept for 4 hours, and then lowered to room temperature at a cooling rate of 50-60°C/h to complete crystal annealing.
  • the raw material powder of lithium carbonate and the binder in a weight ratio of 1:0.8 to 1:1, and use a mixer to stir evenly.
  • the stirring rate is 20rpm/min and the stirring time is 10min to prepare a slurry for polarization.
  • the crystal is cleaned with alcohol, and the polarization direction is confirmed according to the crystal axis.
  • the smearing position of the polarization medium of the head-tail polarization crystal is the upper and lower ends of the crystal, and the smearing range is ⁇ *R 2 (R is the crystal radius); the side polarization crystal
  • the smearing position of the polarizing medium is the long axis of the crystal, and the size of the smearing range is L*2/3*D (L is the height of the crystal, D is the diameter of the crystal), and then the gold wire is buried in the middle of the polarizing medium, and the head and tail of the crystal are polarized.
  • the wire is wound into a circular spiral shape, and the side polarized crystal gold is wound into a rectangular spiral shape.
  • the wiring spacing is required to be 3-5mm, and the size is consistent with the size of the polarized medium. It is quickly dried to make polarized crystal caps.
  • the binder is CMC glue.
  • the lithium tantalate crystal is polarized by applying a current at a rate, and the current value required for the head and tail polarization is 1.2* ⁇ *R 2 (1.2 is the crystal polarization coefficient unit Ma/mm2, R is the crystal radius unit mm), The current value required for side polarization is 1.5*L*D (1.5 is the crystal polarization coefficient unit Ma/mm 2 , L is the crystal height unit mm, D is the crystal diameter unit mm), stop adding current after reaching the required current value, After holding for 4h, cool down at 50-60°C/h. When the temperature is lower than 600°C, turn off the polarization current and wait for the crystal to drop to room temperature.
  • the large-size lithium tantalate crystal produced in this comparative example was inspected with a laser pointer and found that the crystal permeability was poor. After the crystal slice was corroded and domainized, it was found that the overall domain of the crystal was not completely reversed, and the direction consistency was poor. The reason for the analysis is that the temperature is low and the optimal polarization temperature point is not reached.

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Abstract

本发明涉及压电晶体技术领域，尤其是一种大尺寸钽酸锂晶体单畴化方法，包括以下步骤：a)将钽酸锂晶体放于高温炉内，升温至1350℃，保温4h，完成晶体退火，降至常温；b)将碳酸锂原料粉末、粘结剂按1：0.8～1：1的比例混合制成极化浆液，涂抹于退火完钽酸锂晶体的极化两端，再把极化用黄金丝埋于极化浆液内，迅速烘干，制成极化晶帽；c)将退火完的钽酸锂晶体按50-60℃/h的升温速率升温，并使用电阻测试仪记录钽酸锂晶体电阻变化，当温度超过600℃，电阻变化速率变小，达到2Ω/10℃时，暂停升温，PLC施加电流对钽酸锂晶体进行极化操作，当极化电流达到要求值时，停止加电流，保温4h，按50-60℃/h的降温，当温度低于600℃时，关闭极化电流，继续降至常温。

Description

一种大尺寸钽酸锂晶体单畴化方法 技术领域
本发明涉及压电晶体领域，具体领域为一种大尺寸钽酸锂晶体单畴化方法。
背景技术
近年来，由于高频段、多频段通信在以手机为代表的无线通信上的广泛使用，对于声表面波滤波器(SAW)的需求大幅增加，其质量要求也更高。随着声表面波技术的不断发展，声表面波器件的应用领域不断扩大，市场前景越来越广阔，仅声表面波滤波器就可以看到其广阔的市场前景。从20世纪90年代开始，声表面波滤波器在手机上的应用增长非常迅速，每部智能手机需要声表面波器件至少6个。2016年全球手机市场对声表面波滤波器件年需求在84亿只以上，而且还在高速增长。随着互联网的迅猛发展，全球上网的用户愈来愈多，高性能的声表面波滤波器在基于有线电视网的宽带多媒体数据广播系统(如VOD等)方面的应用也迅速发展起来。另外，在汽车电子市场、无线LAN及数字电视的传输系统中，也需要大量的中频声表面波滤波器。而多频段的使用则增加了单个设备中SAW器件的数量，增加了SAW器件的市场需求。同时，通讯器材的小型化，要求各个部件制作更为精密，使SAW同样趋于小型化。
随着对于SAW器件需求的与日俱增，晶体端也逐渐趋向于大尺寸方向发展，而在大尺寸钽酸锂晶体退火极化过程中，钽酸锂晶体的极化介质在尺寸放大后存在高温脱落导致单畴化效果变差现象；大尺寸钽酸锂晶体在以原温度工艺极化后，单畴化效果不完全，但极化温度在提升后，晶体又存在高温开裂现象；这些问题严重影响了大尺寸钽酸锂晶体的压电性能和生产制造成本。
针对上述存在的问题，现有的中国专利文献公开了一种掺杂铌酸锂晶体极化工艺及其装置，专利号：93110359.2，提到通过磨平晶体极化端面和磨平极化陶瓷板以解决接触问题，提升单畴化效果，此操作过程复杂且靠压块固定粘合度差，以温度作为极化点，易造成晶体开裂。
发明内容
本发明的目的在于提供一种大尺寸钽酸锂晶体单畴化方法。
为实现上述目的，本发明提供如下技术方案：
一种大尺寸钽酸锂晶体单畴化方法，包括以下步骤：
a)将钽酸锂晶体放于高温炉内，按50-60℃/h的升温速率升温至1350℃，保温4h，完成晶体退火，并按50-60℃/h的降温速率降至常温；
b)将碳酸锂原料粉末、粘结剂按1：0.8～1：1的重量比例混合，并使用搅拌机搅拌均匀，制成极化用浆液，将混合成的极化浆液涂抹于退火完钽酸锂晶体的极化两端，采用黄金丝作为极化电极，迅速烘干，制成极化晶帽；
c)将退火完的钽酸锂晶体按50-60℃/h的升温速率升温，通过电阻测试仪记录钽酸锂晶体电阻变化，当温度超过600℃，电阻变化速率变小，达到2Ω/10℃时，暂停升温，PLC按5Ma/min的速率施加电流对钽酸锂晶体进行极化操作，当极化电流达到要求值时，停止加电流，保温4h，按50-60℃/h的降温，当温度低于600℃时，关闭极化电流，继续降至常温。
其中，步骤b)中，极化介质采用碳酸锂原料粉末和粘结剂按1：0.8～1：1的重量比例混合成浆液制成，粘结剂为CMC胶水。
其中，碳酸锂原料纯度要求99.99％。
其中，步骤b)中，黄金丝埋于极化介质中间，头尾极化晶体黄金丝绕成圆形螺旋状，侧面极化晶体黄金绕成矩形螺旋状，黄金丝直径要求1mm，布线间距要求3-5mm，大小与极化介质大小一致。
其中，步骤c)中，钽酸锂晶体极化最佳点通过电阻测试仪根据电阻变化确认，通过PLC调节电流大小自动控制，钽酸锂晶体极化电流要求值：头尾极化要求达到的电流值为1.2*π*R2(1.2为晶体极化系数，单位Ma/mm 2，R为晶体半径，单位mm)，侧面极化要求的电流值为1.5*L*D(1.5为晶体极化系数，单位Ma/mm 2，L为晶体高度，单位mm，D为晶体直径，单位mm)。
与现有技术相比，本发明的有益效果是：
(1)本工艺通过碳酸锂原料粉末和粘结剂混合制成极化用浆液，粘结剂采用CMC胶水，具有粘性好、干燥快、高温不脱落、不与晶体反应优点，且由于极化介质采用浆液设计，提升了极化介质接触面的牢固性和极化介质接触面的贴合性，能有效防止介质的脱落。
(2)本工艺通过黄金丝埋于极化介质内的布线形式，可以减小高温环境对黄金丝的导电性影响和黄金丝高温脱落问题，使极化电流的控制更加稳定，从而有效的降低大尺寸钽酸锂晶体的开裂率，提升晶体的单畴化效果。
(3)本工艺通过电阻测试方法以电阻变化率来确定最佳极化点，并对头尾极化晶体和侧面极化晶体的极化系数做了区分，可以实现在保证晶体完整性的同时达到最佳极化效果。
附图说明
图1为实施例1晶体极化示意图；其中，1-极化介质，2-黄金丝极化电极，3-极化线路，4-PLC极化控制器，5-电阻测试仪，6-钽酸锂晶体。
图2为实施例1中钽酸锂晶体极化温度与电阻关系图；其中，650℃处的黑色圆点为极化点。
具体实施方式
下面将对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
实施例1
一种大尺寸钽酸锂晶体单畴化方法，包括以下步骤：
(1)晶体退火：
将退火用陶瓷坩埚底部铺上钽酸锂原料粉末，粉末目数要求为20-30目，再把钽酸锂晶体底部埋于钽酸锂原料粉末内固定，放入高温炉内，按50-60℃/h的升温速率升温至 1350℃，保温4h，再按50-60℃/h的降温速率降至常温，完成晶体退火。
(2)极化晶帽制作：
将碳酸锂原料粉末、粘结剂按1：0.8～1：1的重量比例混合，并使用搅拌机搅拌均匀，搅拌速率为20rpm/min，搅拌时间为10min，制成极化用浆液，把退火完晶体使用酒精擦洗干净，根据晶体轴向确认极化方向，其中头尾极化晶体的极化介质涂抹位置为晶体上下端面，涂抹范围大小为π*R 2(R为晶体半径)；侧面极化晶体的极化介质涂抹位置为晶体长轴，涂抹范围大小为L*2/3*D(L为晶体高度，D为晶体直径)，再把黄金丝埋于极化介质中间，头尾极化晶体黄金丝绕成圆形螺旋状，侧面极化晶体黄金绕成矩形螺旋状，布线间距要求3-5mm，大小与极化介质大小一致。迅速烘干制成极化晶帽。
其中，粘结剂为CMC胶水。
(3)晶体极化：
如图1及图2所示，将待极化钽酸锂晶体固定在极化座上，连接好极化线路，按50-60℃/h的升温速率升温，当温度超过居里温度(600℃)后，使用电阻测试仪连接极化线路的正负极两端进行电阻测试，记录钽酸锂晶体电阻变化，当电阻变化速率变小，达到2Ω/10℃时，暂停升温，开启PLC按5MA/min的速率施加电流对钽酸锂晶体进行极化操作，其中头尾极化要求达到的电流值为1.2*π*R 2(1.2为晶体极化系数单位Ma/mm 2，R为晶体半径单位mm)，侧面极化要求的电流值为1.5*L*D(1.5为晶体极化系数单位Ma/mm 2，L为晶体高度单位mm，D为晶体直径单位mm)，到达要求电流值后停止加电流，保温4h后，按50-60℃/h降温，温度低于600℃时，关闭极化电流，待晶体降至常温。
本实施例产出的大尺寸钽酸锂晶体，极化介质、黄金丝未出现脱落现象，使用激光笔检验发现晶体整体通透性好，晶体切片腐蚀畴化后使用晶相显微镜发现晶体畴翻转完全，均匀分布，方向一致。
为突出本发明的有益效果，还进行了以下对比例实验。
对比例1
一种大尺寸钽酸锂晶体单畴化方法，包括以下步骤：
(1)晶体退火：
将退火用陶瓷坩埚底部铺上钽酸锂原料粉末，粉末目数要求为20-30目，再把钽酸锂晶体底部埋于钽酸锂原料粉末内固定，放入高温炉内，按50-60℃/h的升温速率升温至1350℃，保温4h，再按50-60℃/h的降温速率降至常温，完成晶体退火。
(2)极化晶帽制作：
将碳酸锂压制成厚度为5mm的极化介质，把退火完晶体使用酒精擦洗干净，根据晶体轴向确认极化方向，其中头尾极化晶体极化介质固定位置为晶体上下端面，范围大小为π*R 2(R为晶体半径)；侧面极化晶体极化介质固定位置为晶体长轴，范围大小为L*2/3*D(L为晶体高度，D为晶体直径)，再把极化用黄金片固定在极化介质上，制成极化晶帽。
(3)晶体极化：
将待极化钽酸锂晶体固定在极化座上，连接好极化线路，按50-60℃/h的升温速率升温，当温度超过居里温度(600℃)后，使用电阻测试仪连接极化线路的正负极两端进行电阻测试，记录钽酸锂晶体电阻变化，当电阻变化速率变小，达到2Ω/10℃时，暂停升温，开启PLC按5Ma/min的速率施加电流对钽酸锂晶体进行极化操作，其中头尾极化要求达到的电流值为1.2*π*R 2(1.2为晶体极化系数单位Ma/mm 2，R为晶体半径单位mm)，侧面极化要求的电流值为1.5*L*D(1.5为晶体极化系数单位Ma/mm 2，L为晶体高度单位mm，D为晶体直径单位mm)，到达要求电流值后停止加电流，保温4h后，按50-60℃/h降温，温度低于600℃时，关闭极化电流，待晶体降至常温。
本对比例产出的大尺寸钽酸锂晶体，极化介质、黄金片均出现了部分脱落或位置移动现象，使用激光笔检验发现晶体部分区域通透性较差，晶体切片腐蚀畴化后使用晶相显微镜发现晶体部分区域畴未完全翻转，方向一致性较差。
对比例2
一种大尺寸钽酸锂晶体单畴化方法，包括以下步骤：
(1)晶体退火：
将退火用陶瓷坩埚底部铺上钽酸锂原料粉末，粉末目数要求为20-30目，再把钽酸锂晶体底部埋于钽酸锂原料粉末内固定，放入高温炉内，按50-60℃/h的升温速率升温至1350℃，保温4h，再按50-60℃/h的降温速率降至常温，完成晶体退火。
(2)极化晶帽制作：
将碳酸锂原料粉末、粘结剂按1：0.8～1：1的重量比例混合，并使用搅拌机搅拌均匀，搅拌速率为20rpm/min，搅拌时间为10min，制成极化用浆液，把退火完晶体使用酒精擦洗干净，根据晶体轴向确认极化方向，其中头尾极化晶体极化介质涂抹位置为晶体上下端面，涂抹范围大小为π*R 2(R为晶体半径)；侧面极化晶体极化介质涂抹位置为晶体长轴，涂抹范围大小为L*2/3*D(L为晶体高度，D为晶体直径)，再把黄金丝埋于极化介质中间，迅速烘干制成极化晶帽。
其中，粘结剂为CMC胶水。
(3)晶体极化：
将待极化钽酸锂晶体固定在极化座上，连接好极化线路，按50-60℃/h的升温速率升温，当温度超过居里温度(600℃)后，使用电阻测试仪连接极化线路的正负极两端进行电阻测试，记录钽酸锂晶体电阻变化，当电阻变化速率变小，达到2Ω/10℃时，暂停升温，开启PLC按5Ma/min的速率施加电流对钽酸锂晶体进行极化操作，其中头尾极化要求达到的电流值为1.2*π*R2(1.2为晶体极化系数单位Ma/mm2，R为晶体半径单位mm)，侧面极化要求的电流值为1.5*L*D(1.5为晶体极化系数单位Ma/mm2，L为晶体高度单位mm，D为晶体直径单位mm)，到达要求电流值后停止加电流，保温4h后，按50-60℃/h降温，温度低于600℃时，关闭极化电流，待晶体降至常温。
本对比例产出的大尺寸钽酸锂晶体，使用激光笔检验发现晶体部分区域通透性较差，晶体切片腐蚀畴化后使用晶相显微镜发现晶体部分区域畴未完全翻转，方向一致性较差。分析原因为黄金丝未均匀布线，导致部分区域电流分布不均匀。
对比例3
一种大尺寸钽酸锂晶体单畴化方法，包括以下步骤：
(1)晶体退火：
将退火用陶瓷坩埚底部铺上钽酸锂原料粉末，粉末目数要求为20-30目，再把钽酸锂晶体底部埋于钽酸锂原料粉末内固定，放入高温炉内，按50-60℃/h的升温速率升温至1350℃，保温4h，再按50-60℃/h的降温速率降至常温，完成晶体退火。
(2)极化晶帽制作：
将碳酸锂原料粉末、粘结剂按1：0.8～1：1的重量比例混合，并使用搅拌机搅拌均匀，搅拌速率为20rpm/min，搅拌时间为10min，制成极化用浆液，把退火完晶体使用酒精擦洗干净，根据晶体轴向确认极化方向，其中头尾极化晶体极化介质涂抹位置为晶体上下端面，涂抹范围大小为π*R 2(R为晶体半径)；侧面极化晶体极化介质涂抹位置为晶体长轴，涂抹范围大小为L*2/3*D(L为晶体高度，D为晶体直径)，黄金丝埋于极化介质中间，头尾极化晶体黄金丝绕成圆形螺旋状，侧面极化晶体黄金绕成矩形螺旋状，布线间距要求3-5mm，大小与极化介质大小一致。迅速烘干制成极化晶帽。
其中，粘结剂为CMC胶水。
(3)晶体极化：
将待极化钽酸锂晶体固定在极化座上，连接好极化线路，按50-60℃/h的升温速率升温，当温度达到660℃时，暂停升温，开启PLC按5Ma/min的速率施加电流对钽酸锂晶体进行极化操作，其中头尾极化要求达到的电流值为1.2*π*R 2(1.2为晶体极化系数单位Ma/mm2，R为晶体半径单位mm)，侧面极化要求的电流值为1.5*L*D(1.5为晶体极化系数单位Ma/mm 2，L为晶体高度单位mm，D为晶体直径单位mm)，到达要求电流值后停止加电流，保温4h后，按50-60℃/h降温，温度低于600℃时，关闭极化电流，待晶体降至常温。
本对比例产出的大尺寸钽酸锂晶体，出现了内部开裂现象，判断为以温度极化时，温度过高造成晶体开裂。
对比例4
一种大尺寸钽酸锂晶体单畴化方法，包括以下步骤：
(1)晶体退火：
将退火用陶瓷坩埚底部铺上钽酸锂原料粉末，粉末目数要求为20-30目，再把钽酸锂晶体底部埋于钽酸锂原料粉末内固定，放入高温炉内，按50-60℃/h的升温速率升温至1350℃，保温4h，再按50-60℃/h的降温速率降至常温，完成晶体退火。
(2)极化晶帽制作：
将碳酸锂原料粉末、粘结剂按1：0.8～1：1的重量比例混合，并使用搅拌机搅拌均匀，搅拌速率为20rpm/min，搅拌时间为10min，制成极化用浆液，把退火完晶体使用酒精擦洗干净，根据晶体轴向确认极化方向，其中头尾极化晶体极化介质涂抹位置为晶体上下端面，涂抹范围大小为π*R 2(R为晶体半径)；侧面极化晶体极化介质涂抹位置为晶体长轴，涂抹范围大小为L*2/3*D(L为晶体高度，D为晶体直径)，再把黄金丝埋于极化介质中间，头尾极化晶体黄金丝绕成圆形螺旋状，侧面极化晶体黄金绕成矩形螺旋状，布线间距要求3-5mm，大小与极化介质大小一致。迅速烘干制成极化晶帽。
其中，粘结剂为CMC胶水。
(3)晶体极化：
将待极化钽酸锂晶体固定在极化座上，连接好极化线路，按50-60℃/h的升温速率升温，当温度达到630℃时，暂停升温，开启PLC按5Ma/min的速率施加电流对钽酸锂晶体进行极化操作，其中头尾极化要求达到的电流值为1.2*π*R 2(1.2为晶体极化系数单位Ma/mm2，R为晶体半径单位mm)，侧面极化要求的电流值为1.5*L*D(1.5为晶体极化系数单位Ma/mm 2，L为晶体高度单位mm，D为晶体直径单位mm)，到达要求电流值后停止加电流，保温4h后，按50-60℃/h降温，温度低于600℃时，关闭极化电流，待晶体降至常温。
本对比例产出的大尺寸钽酸锂晶体，使用激光笔检验发现晶体通透性较差，晶体切片 腐蚀畴化后使用晶相显微镜发现晶体整体畴未完全翻转，方向一致性较差。分析原因为温度较低，未达到最佳极化温度点。
尽管已经示出和描述了本发明的实施例，对于本领域的普通技术人员而言，可以理解在不脱离本发明的原理和精神的情况下可以对这些实施例进行多种变化、修改、替换和变型，本发明的范围由所附权利要求及其等同物限定。

Claims (8)

  1. 一种大尺寸钽酸锂晶体单畴化方法，其特征在于：包括以下步骤：
    a)将钽酸锂晶体放于高温炉内，按50-60℃/h的升温速率升温至1350℃，保温4h，完成晶体退火，并按50-60℃/h的降温速率降至常温；
    b)将碳酸锂原料粉末、粘结剂使用搅拌机搅拌均匀，制成极化浆液，将混合成的极化浆液涂抹于退火完钽酸锂晶体的极化两端，采用黄金丝作为极化电极，迅速烘干，制成极化晶帽；
    c)将退火完的钽酸锂晶体按50-60℃/h的升温速率升温，记录钽酸锂晶体电阻变化，当温度超过600℃，电阻变化速率变小，达到2Ω/10℃时，暂停升温，PLC按5Ma/min的速率施加电流对钽酸锂晶体进行极化操作，当极化电流达到要求值时，停止加电流，保温4h，按50-60℃/h的降温，当温度低于600℃时，关闭极化电流，继续降至常温。
  2. 根据权利要求1所述的大尺寸钽酸锂晶体单畴化方法，其特征在于：步骤b)中，碳酸锂原料粉末和粘结剂的重量比例为1：0.8～1：1。
  3. 根据权利要求2所述的大尺寸钽酸锂晶体单畴化方法，其特征在于：所述粘结剂为CMC胶水。
  4. 根据权利要求3所述的大尺寸钽酸锂晶体单畴化方法，其特征在于：碳酸锂原料纯度要求99.99％。
  5. 根据权利要求1所述的大尺寸钽酸锂晶体单畴化方法，其特征在于：步骤b)中，极化黄金丝埋于极化浆液内。
  6. 根据权利要求4所述的大尺寸钽酸锂晶体单畴化方法，其特征在于：黄金丝直径要求1mm，头尾极化晶体黄金丝绕成圆形螺旋状，侧面极化晶体黄金绕成矩形螺旋状，大小与极化介质一致，布线间距要求3-5mm。
  7. 根据权利要求1所述的大尺寸钽酸锂晶体单畴化方法，其特征在于：步骤c)中，钽酸锂晶体极化最佳点通过电阻测试仪根据电阻变化确认，通过PLC调节电流大小自动控制。
  8. 根据权利要求1所述的大尺寸钽酸锂晶体单畴化方法，其特征在于：步骤c)中， 钽酸锂晶体极化电流要求值为：头尾极化要求达到的电流值为1.2*π*R 2，其中1.2为晶体极化系数，单位Ma/mm 2，R为晶体半径，单位mm；侧面极化要求的电流值为1.5*L*D，1.5为晶体极化系数，单位Ma/mm 2；L为晶体高度，单位mm；D为晶体直径，单位mm。
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