CN117822117A - Rare earth doped potassium sodium niobate monocrystal and cosolvent-free rapid growth method based on stoichiometric ratio components - Google Patents
Rare earth doped potassium sodium niobate monocrystal and cosolvent-free rapid growth method based on stoichiometric ratio components Download PDFInfo
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 14
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 11
- 239000013078 crystal Substances 0.000 claims abstract description 115
- 239000011734 sodium Substances 0.000 claims abstract description 32
- 239000000155 melt Substances 0.000 claims abstract description 15
- 241000357437 Mola Species 0.000 claims abstract description 6
- 239000000463 material Substances 0.000 claims description 42
- 239000002994 raw material Substances 0.000 claims description 25
- 238000005245 sintering Methods 0.000 claims description 20
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 18
- 239000010955 niobium Substances 0.000 claims description 16
- 239000007790 solid phase Substances 0.000 claims description 15
- 238000002360 preparation method Methods 0.000 claims description 14
- 238000001291 vacuum drying Methods 0.000 claims description 14
- 229910052697 platinum Inorganic materials 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 5
- 230000008859 change Effects 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- 239000006184 cosolvent Substances 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 4
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- 229910052779 Neodymium Inorganic materials 0.000 claims description 3
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- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 2
- 238000004140 cleaning Methods 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 claims description 2
- -1 niobium rare earth Chemical class 0.000 claims description 2
- 238000010899 nucleation Methods 0.000 claims description 2
- 238000010583 slow cooling Methods 0.000 claims description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 28
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- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000010453 quartz Substances 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
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- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910052797 bismuth Inorganic materials 0.000 description 2
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
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- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
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- 150000002500 ions Chemical class 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 229910052451 lead zirconate titanate Inorganic materials 0.000 description 1
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
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- 230000004048 modification Effects 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- ZBSCCQXBYNSKPV-UHFFFAOYSA-N oxolead;oxomagnesium;2,4,5-trioxa-1$l^{5},3$l^{5}-diniobabicyclo[1.1.1]pentane 1,3-dioxide Chemical compound [Mg]=O.[Pb]=O.[Pb]=O.[Pb]=O.O1[Nb]2(=O)O[Nb]1(=O)O2 ZBSCCQXBYNSKPV-UHFFFAOYSA-N 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- CHWRSCGUEQEHOH-UHFFFAOYSA-N potassium oxide Chemical compound [O-2].[K+].[K+] CHWRSCGUEQEHOH-UHFFFAOYSA-N 0.000 description 1
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- 229910001948 sodium oxide Inorganic materials 0.000 description 1
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Abstract
The invention relates to a rare earth doped potassium sodium niobate based crystal and a method for rapidly growing stoichiometric components, wherein the crystal growth is carried out by a melt pulling method, and the molecular formula of the potassium sodium niobate monocrystal is (K) 1‑ x Na x )NbO 3 Y% molA, x is more than or equal to 0.3 and less than or equal to 0.7,0, Y is more than or equal to 5, and A is Li, la, ce, pr, nd, pm, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, sc or an oxide of Y element. The method of the invention effectively solves the problems of long growth period, small size, poor quality and the like of the existing potassium sodium niobate single crystal, and further improves the quality by doping rare earth elementsThe piezoelectric properties of the potassium sodium niobate single crystal are improved.
Description
Technical Field
The invention particularly relates to a rare earth doped potassium sodium niobate monocrystal and a cosolvent-free rapid growth method based on stoichiometric ratio components, belonging to the field of piezoelectric crystal materials.
Background
The piezoelectric material can be used as a medium to realize the mutual conversion of mechanical energy and electric energy due to the unique crystal structure, and is further designed into various functional devices, such as a transducer, a driver, a filter and an ultrasonic motor, which are applied to various fields of medical treatment, communication, energy sources, military, daily life and the like. However, piezoelectric materials mainly used in this field have been lead-containing materials such as lead zirconate titanate, lead magnesium niobate, and the like. The material composition contains a large amount of lead elements, which can cause great harm to human bodies and the environment, so that the development of the high-performance lead-free piezoelectric material becomes a very urgent task. In the ceramic field, potassium sodium niobate based ceramics have been widely demonstrated to have good electrical properties and higher curie temperatures, and are considered to be one of the most likely piezoelectric material systems to replace lead based materials. Compared to ceramics, single crystals have a more dense structure, fewer defects and their characteristic anisotropy. In addition, the single crystal material has no grain boundary and randomly oriented grains, so that the microscopic domain structure in the single crystal material is easier to reverse to the direction of an electric field during polarization, and the single crystal material has better electromechanical coupling performance and piezoelectric performance in a macroscopic sense.
Because the phase diagram of the potassium sodium niobate system is complex, the segregation coefficients of potassium and sodium are greatly different in the growth process, so that the growth of potassium sodium niobate single crystals is very difficult. The potassium sodium niobate system is generally considered to be a non-uniform molten solid solution, and currently, the mainstream growth method of potassium sodium niobate single crystals is to grow single crystals by adding a fluxing agent. Although the addition of the fluxing agent reduces the growth temperature and thermal stress of crystal growth, the defects of irreparable exist as well: small crystal size, long growth period, etc., such as: chinese patent document CN103966659A discloses a process for preparing potassium sodium niobate single crystals, which employs a top seed (preference<001>Direction KNN single crystal) flux pulling method. The crystal size grown in the specific example was phi 30mm x 10mm, the crystal size was still small, and the growth rate was slow (1.2 mm/day). In addition, the use of fluxing agents introduces impurity ions/atoms to some extent, even self-fluxing agent Na 2 CO 3 、K 2 CO 3 Can also generate adverse effect in the growth process due to the volatile property of potassium oxide and sodium oxide, and is the most importantEventually, the problems of crystal cracking, poor overall quality and the like are caused.
There are reports of growing potassium sodium niobate single crystals without relying on a cosolvent, such as a crucible lowering method and a solid phase reaction method, but these two methods have more remarkable drawbacks. In the crucible descending method, the grown crystals are poor in quality and often have the problems of large internal stress and multiple defects because the crystals are in direct contact with the crucible and cannot be observed and regulated in real time in the growth process. The solid phase reaction method is difficult to control the growth process, so that the grown crystals are small and have more defects, and are difficult to use in a large range. Such as: chinese patent document CN107268084A discloses a potassium sodium niobate-sodium bismuth zirconate leadless piezoelectric monocrystal and a growth method thereof, wherein the whole crystal is severely cracked and has poor quality; CN104357910a discloses a potassium sodium niobate-based single crystal and a preparation method thereof, and the obtained single crystal has an irregular shape and a size of only 10mm, because of the difficulty in obtaining a large-size and high-quality single crystal due to the limitation of the method.
Therefore, how to efficiently and rapidly grow high-quality large-size potassium sodium niobate single crystals is still a problem to be studied and solved.
Disclosure of Invention
Aiming at the problems that the existing growth method of potassium sodium niobate single crystal has low efficiency, small size and many defects, and can not grow high-quality and large-size potassium sodium niobate single crystal efficiently and rapidly, the invention provides a rare earth doped potassium sodium niobate single crystal and a rapid growth method based on stoichiometric ratio components without cosolvent.
The invention is realized by the following technical scheme:
a method for quickly growing rare earth doped potassium sodium niobate monocrystal based on stoichiometric ratio components without cosolvent, wherein the molecular formula of the rare earth doped potassium sodium niobate monocrystal is (K) 1-x Na x )NbO 3 Y% molA, x is more than or equal to 0.1 and less than or equal to 0.9, Y is more than or equal to 0 and less than or equal to 5, and A is Li, la, ce, pr, nd, pm, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, sc or oxide of Y element;
the rapid growth method comprises the following steps:
(1) Selection and treatment of raw materials
a. According to niobium thinMolecular formula (K) of earth doped potassium sodium niobate monocrystal 1-x Na x )NbO 3 -stoichiometric ratio of y% molA, na with purity of 99.99% was weighed 2 CO 3 、K 2 CO 3 And Nb (Nb) 2 O 5 Vacuum drying raw materials, and adding solid oxide or carbonate mixed raw materials of element A during doping;
b. mixing the mixed raw materials for 24-48 hours by using a mixer, enabling the mixed raw materials to be in a uniform state, pressing the mixed raw materials into a cake shape, and obtaining potassium sodium niobate polycrystal materials by adopting a solid phase sintering method;
(2) Preparation for crystal growth
a. Adding the potassium sodium niobate polycrystal material into a growth crucible in batches and in batches;
b. ultrasonically cleaning the directional seed crystal, and assembling the directional seed crystal with a seed rod after drying;
c. loading seed rods and a temperature field matched with growth into a growth furnace;
(3) Cosolvent-free melt pulling method for growing crystals
a. Heating to slowly melt the potassium sodium niobate polycrystal material, and keeping the temperature for 1-2 hours after the polycrystal material is completely melted;
b. regulating the seeding temperature, slowly lowering the potassium sodium niobate seed crystal to the surface of the melt, and carrying out neck collecting, shoulder placing and constant diameter growth; e. after the crystal grows to the required size, slowly lifting the crystal to a position 5mm away from the liquid surface of the melt;
f. cooling to room temperature, and taking out the crystal.
According to the present invention, preferably, in the step (1) a, the rare earth doped potassium sodium niobate single crystal has a molecular formula (K 1-x Na x )NbO 3 -y％molA，0.3≤x≤0.7，0<y.ltoreq.2, A being an oxide of Li, nd, sm, gd, tb, yb alone or an oxide co-doped with Li and Nd, sm, gd, tb, yb.
According to the present invention, it is preferable that the temperature of the vacuum drying in the step (1) a is 100 to 200℃and the drying time is 1 to 3 hours.
According to the invention, in the step (1) b, preferably, the sintering temperature for synthesizing the potassium sodium niobate polycrystal material by the solid phase sintering method is 800-1000 ℃ and the sintering time is 10-30 hours.
According to the present invention, preferably, the sodium potassium niobate seed of step (2) b employs a <100> oriented seed.
According to the present invention, preferably, in the step (2) a, the growth crucible is a platinum crucible, and the height and diameter of the platinum crucible are the same.
According to the invention, preferably, in step (2) a, the polycrystalline material is added in an amount such that the completely melted melt exceeds 5/6 of the growth crucible volume.
According to the present invention, it is preferable that in the step (3), the pulling speed is 0.5 to 20mm/h and the rotation speed is 8 to 20rpm at the time of crystal growth.
The doping of specific elements can be matched with a melt pulling method to rapidly grow potassium sodium niobate monocrystal with high quality.
According to the present invention, it is preferable that in the step (3), the thermal field lateral temperature gradient is small at the time of crystal growth, so that the solid-liquid interface temperature variation is small.
According to the invention, in step (3) f, the cooling rate is preferably from 5 to 20 ℃/h. The slow cooling can effectively reduce the internal stress of the crystal and provide sufficient time for the ferroelectric domains to be uniformly distributed.
According to the invention, in the step (2) and the step (3), the growth atmosphere is preferably air, and the hearth of the growth furnace is in a communication state with the outside. Oxygen partial pressure in air can effectively reduce oxygen vacancy formation in the crystal, and greatly reduce growth cost.
The invention is not described in detail and is in accordance with the prior art.
As can be seen from the analysis of the phase diagram of the potassium sodium niobate system, only the pure potassium sodium niobate phase exists, and no secondary phase is separated out to destroy the growth process; on the basis of widely investigating the existing growth method and researching the characteristics of a melt, the invention designs the polycrystalline material component according to different segregation coefficients in the K, na growth process, and can monitor and improve the characteristics of crystal growth conditions in real time by matching with the melt pulling method, and has small transverse temperature gradient during crystal growth, so that the temperature change of a solid-liquid interface is small, the method for rapidly growing potassium sodium niobate monocrystal based on stoichiometric ratio components is successfully obtained, and in addition, the great improvement of the performance of the potassium sodium niobate piezoelectric monocrystal is realized by doping element A. The method improves the current situation that the existing potassium sodium niobate monocrystal has small growth size, long period and easy cracking. The crystal growth is carried out by a melt pulling method, the phase change behavior is improved without fluxing agent in the growth process, the whole of the obtained crystal is uniform and has no cracking, the bottleneck problem that high-quality large-size potassium sodium niobate single crystals cannot be efficiently and rapidly grown at present is solved, and the obtained single crystals have excellent piezoelectric performance.
The invention has the technical characteristics and advantages that:
1. the invention designs the polycrystalline material components according to different segregation coefficients in the growth process of K, na, and is matched with a melt pulling method to obtain high-quality and large-size potassium sodium niobate monocrystal.
2. Compared with the existing potassium sodium niobate crystal growth method, the method removes the use of fluxing agent and protective gas, the growth atmosphere is air, the hearth of the growth furnace is communicated with the outside, oxygen partial pressure in the air can effectively reduce the formation of oxygen vacancies in the crystal, high-quality single crystal is obtained, the step of single crystal growth is simpler and more convenient, and the cost is reduced.
3. The potassium sodium niobate monocrystal grown by the method has excellent piezoelectric performance, and the monocrystal is uniformly distributed and has no cracking. Effectively solves the problems of poor crystallization quality, serious cracking condition and the like of the existing potassium sodium niobate crystal.
4. According to the invention, by doping the element A and matching with a melt pulling method, high-quality large-size potassium sodium niobate single crystal is efficiently and rapidly obtained, the performance of a potassium sodium niobate system single crystal is greatly improved, and a solid foundation is laid for further improvement of the performance of the potassium sodium niobate system single crystal in the future.
Drawings
FIG. 1 is a schematic diagram of an apparatus for growing crystals by the melt pulling method. In the figure, (1) an induction heating coil, (2) a quartz sleeve, (3) zirconia cotton, (4) a zirconia sleeve, (5) a zirconia plate, (6) a zirconia support, (7) zirconia sand, (8) a platinum crucible, (9) seed crystal, and (3) a lifting rod.
FIG. 2 is a photograph of pure potassium sodium niobate single crystal prepared in example 1 and piezoelectric properties thereof;
FIG. 3 is a photograph of Li-doped potassium sodium niobate single crystal prepared in example 3 and piezoelectric properties;
FIG. 4 is a photograph of Nd-doped potassium-sodium niobate single crystal prepared in example 6 and piezoelectric properties;
FIG. 5 is a photograph of a Li-Sm co-doped potassium sodium niobate single crystal prepared in example 9 and piezoelectric properties thereof;
FIG. 6 is a photograph of a Li-Nd co-doped potassium sodium niobate single crystal prepared in example 10 and its piezoelectric properties;
FIG. 7 is a photograph of a Li-Gd co-doped potassium sodium niobate single crystal prepared in example 11 and piezoelectric properties.
Detailed Description
The following describes in detail the examples of the present invention, which are implemented on the premise of the technical proposal of the present invention, and the detailed implementation and specific operation procedure are given, but the protection scope of the present invention is not limited to the following examples.
The device for growing crystals by a melt pulling method in the embodiment is structurally characterized by comprising a quartz sleeve (2), wherein an induction heating coil (1) is wound on the periphery of the quartz sleeve, a zirconia support (6) is arranged at the inner bottom of the quartz sleeve (2), zirconia sand (7) is filled between the zirconia supports (6), a platinum crucible (8) is arranged on the zirconia plate (5), a zirconia sleeve (4) is arranged outside the platinum crucible (8), zirconia sand (7) is filled between the platinum crucible (8) and the zirconia sleeve (4), and zirconia cotton (3) is arranged outside the zirconia sleeve (4) and used for heat preservation.
Example 1: k (K) 0.8 Na 0.2 NbO 3 Preparation of single crystals
(1) Selection and treatment of raw materials
Na with purity of 99.99% 2 CO 3 、K 2 CO 3 And Nb (Nb) 2 O 5 The material is prepared from the following components in parts by weight: k (K) 0.8 Na 0.2 NbO 3 Weighing the stoichiometric proportion of the ingredients, then placing the ingredients at 120 ℃ for vacuum drying, mixing the mixed raw materials for 30 hours by using a mixer, enabling the mixed raw materials to be in a uniform state, pressing the mixed raw materials into a cake shape, and synthesizing potassium sodium niobate polycrystal materials by adopting a solid phase sintering method, wherein the solid phase sintering temperature is 950 ℃, and the sintering time is 20 hours;
(2) Crystal growth
Adding the obtained polycrystal material into a platinum crucible in batches and times, loading into a pulling furnace, heating to enable the polycrystal material to be melted slowly, and keeping the temperature for 2 hours after the polycrystal material is melted completely; adjusting the power of a power supply to a lower temperature, slowly lowering the potassium sodium niobate seed crystal to the surface of a melt, and carrying out neck-collecting, shoulder-placing and constant diameter growth, wherein the rotation speed of a seed rod in the growth process is 8rpm, the lifting speed is 0.5mm/h, the transverse temperature gradient of a thermal field is small and is less than 2 ℃/cm, so that the temperature change of a solid-liquid interface is small; the growth atmosphere is air, and the hearth of the growth furnace is communicated with the outside; the crystals are lifted off when they grow to the desired size. After the growth is finished, the mixture is cooled to room temperature at a speed of 20 ℃/h. The obtained pure potassium sodium niobate monocrystal has physical photograph and piezoelectric performance shown in figure 2, and the monocrystal size is 13×13×40mm 3 。
Example 2
The procedure is as in example 1, except that:
na with purity of 99.99% 2 CO 3 、K 2 CO 3 And Nb (Nb) 2 O 5 The material is prepared from the following components in parts by weight: k (K) 0.5 Na 0.5 NbO 3 The stoichiometric proportions of (2) were weighed and dried in vacuo at 120℃with the exception that the single crystals obtained were 14X 40mm in size as in example 1 3 。
Example 3: preparation of 1mol% Li-doped potassium sodium niobate single crystal
The procedure is as in example 1, except that:
li with purity of 99.99% 2 CO 3 、Na 2 CO 3 、K 2 CO 3 And Nb (Nb) 2 O 5 The raw materials are prepared according to the following formula: li (Li) 0.01 K 0.79 Na 0.2 NbO 3 Is placed after weighing the stoichiometric ratio of (2)Vacuum drying at 120 deg.c and solid phase sintering to synthesize the required polycrystal material.
The rotation speed of the seed rod during the growth was 10rpm, the pulling speed was 5mm/h, and the temperature was lowered to room temperature at a rate of 15℃per hour after the end of the growth, otherwise, the procedure was as in example 1. The obtained pure potassium sodium niobate monocrystal has physical photograph and piezoelectric performance shown in figure 3, and the monocrystal size is 15×15×40mm 3 。
Example 4: preparation of 3mol% Li-doped potassium sodium niobate monocrystal
The procedure is as in example 1, except that:
li with purity of 99.99% 2 CO 3 、Na 2 CO 3 、K 2 CO 3 And Nb (Nb) 2 O 5 The raw materials are prepared according to the following formula: li (Li) 0.03 K 0.77 Na 0.2 NbO 3 The stoichiometric ratio of (2) is weighed and then placed at 120 ℃ for vacuum drying, and the needed polycrystal material is synthesized by adopting a solid phase sintering method.
The rotation speed of the seed rod during the growth process was 10rpm, the pulling rate was 5mm/h, and after the growth was completed, the temperature was lowered to room temperature at a rate of 15 ℃/h, otherwise, the procedure of example 1 was followed to obtain single crystals having a size of 15X 40mm 3 。
Example 5: preparation of 5mol% Li doped potassium sodium niobate monocrystal
The procedure is as in example 1, except that:
li with purity of 99.99% 2 CO 3 、Na 2 CO 3 、K 2 CO 3 And Nb (Nb) 2 O 5 The raw materials are prepared according to the following formula: li (Li) 0.05 K 0.75 Na 0.2 NbO 3 The stoichiometric ratio of (2) is weighed and then placed at 120 ℃ for vacuum drying, and the needed polycrystal material is synthesized by adopting a solid phase sintering method.
The rotation speed of the seed rod during the growth process was 10rpm, the pulling rate was 5mm/h, and after the growth was completed, the temperature was lowered to room temperature at a rate of 15 ℃/h, otherwise, the procedure of example 1 was followed to obtain single crystals having a size of 15X 40mm 3 。
Example 6: preparation of 0.5mol per mill Nd doped potassium sodium niobate monocrystal
The procedure is as in example 1, except that:
na with purity of 99.99% 2 CO 3 、K 2 CO 3 、Nb 2 O 5 And Nd 2 O 3 The raw materials are prepared according to the following formula: (K) 0.8 Na 0.2 )NbO 3 -0.5‰molNd 2 O 3 The stoichiometric ratio of (2) is weighed and then placed at 120 ℃ for vacuum drying, and the needed polycrystal material is synthesized by adopting a solid phase sintering method.
The rotation speed of the seed rod in the growth process is 12rpm, the pulling speed is 10mm/h, the temperature is reduced to room temperature at the speed of 10 ℃/h after the growth is finished, and the obtained single crystal size is 16 multiplied by 40mm 3 。
Example 7: preparation of 1mol per mill Tb doped potassium sodium niobate monocrystal
As described in example 1, except that:
na with purity of 99.99% 2 CO 3 、K 2 CO 3 、Nb 2 O 5 And Tb 4 O 7 The raw materials are prepared according to the following formula: (K) 0.8 Na 0.2 )NbO 3 -1‰molTb 4 O 7 The stoichiometric ratio of (2) is weighed and then placed at 120 ℃ for vacuum drying, and the needed polycrystal material is synthesized by adopting a solid phase sintering method.
The rotation speed of the seed rod in the growth process is 12rpm, the pulling speed is 10mm/h, the temperature is reduced to room temperature at the speed of 10 ℃/h after the growth is finished, and the obtained single crystal size is 16 multiplied by 40mm 3 。
Example 8: preparation of 2mol per mill Yb doped potassium sodium niobate monocrystal
Na with purity of 99.99% 2 CO 3 、K 2 CO 3 、Nb 2 O 5 And Yb 2 O 3 The raw materials are prepared according to the following formula: (K) 0.8 Na 0.2 )NbO 3 -2‰molYb 2 O 3 The stoichiometric ratio of (2) is weighed and then placed at 120 ℃ for vacuum drying, and the needed polycrystal material is synthesized by adopting a solid phase sintering method.
The rotation speed of the seed rod in the growth process is 12rpm, the pulling speed is 10mm/h, and the seed rod is cooled to room temperature at the speed of 10 ℃/h after the growth is finished, thus obtainingThe obtained single crystal size is 16×16×40mm 3 。
Example 9: preparation of 1% molLi, 0.5 mol%Sm co-doped potassium sodium niobate monocrystal
As described in example 1, except that:
li with purity of 99.99% 2 CO 3 、Na 2 CO 3 、K 2 CO 3 、Nb 2 O 5 And Sm 2 O 3 The raw materials are prepared according to the following formula: (K) 0.79 Na 0.2 Li 0.01 )NbO 3 -0.5‰molSm 2 O 3 The stoichiometric ratio of (2) is weighed and then placed at 120 ℃ for vacuum drying, and a solid phase sintering method is adopted to synthesize potassium sodium niobate polycrystal material.
The rotation speed of the seed rod in the growth process is 12rpm, the pulling speed is 20mm/h, the seed rod is cooled to room temperature at the speed of 5 ℃/h after the growth is finished, and the obtained single crystal size is 18 multiplied by 40mm 3 。
Example 10: preparation of 5% molLi, 0.5 mol%Nd codoped potassium sodium niobate monocrystal
As described in example 1, except that:
li with purity of 99.99% 2 CO 3 、Na 2 CO 3 、K 2 CO 3 、Nb 2 O 5 And Nd 2 O 3 The raw materials are prepared according to the following formula: (K) 0.75 Na 0.2 Li 0.05 )NbO 3 -0.5‰molNd 2 O 3 The stoichiometric ratio of (2) is weighed and then placed at 120 ℃ for vacuum drying, and the needed polycrystal material is synthesized by adopting a solid phase sintering method.
The rotation speed of the seed rod in the growth process is 12rpm, the pulling speed is 20mm/h, the temperature is reduced to room temperature at the speed of 5 ℃/h after the growth is finished, and the obtained single crystal size is 18 multiplied by 40mm 3 。
Example 11: preparation of 3% molLi, 0.5 mol%o Gd co-doped potassium sodium niobate monocrystal
As described in example 1, except that:
li with purity of 99.99% 2 CO 3 、Na 2 CO 3 、K 2 CO 3 、Nb 2 O 5 And Gd 2 O 3 The formula of the raw materials is as follows: (K) 0.77 Na 0.2 Li 0.03 )NbO 3 -0.5‰molGd 2 O 3 The stoichiometric ratio of (2) is weighed and then placed at 120 ℃ for vacuum drying, and the needed polycrystal material is synthesized by adopting a solid phase sintering method.
The rotation speed of the seed rod in the growth process is 12rpm, the pulling speed is 20mm/h, the temperature is reduced to room temperature at the speed of 5 ℃/h after the growth is finished, and the obtained single crystal size is 18 multiplied by 40mm 3 。
Test example 1:
the pure potassium sodium niobate single crystal prepared in example 1 has the piezoelectric properties shown in fig. 2; the 1% doped potassium sodium niobate monocrystal prepared in example 3 has physical photo and piezoelectric performance shown in figure 3, and the small graph is the piezoelectric performance test result after polarization.
As can be seen from fig. 1, the crystal has complete appearance, no cracking, no crack, high quality, large size and high quality,
as can be seen from FIG. 3, the Li-doped potassium sodium niobate crystal obtained by the Czochralski method has complete appearance, no cracking, no crack, high quality, large size, high quality single crystal and high growth speed.
Comparing fig. 1 and 3, it can be seen that doping of Li improves the piezoelectric properties of potassium sodium niobate crystals, and the crystal quality is further improved.
Test example 2:
the photograph of Nd-doped single crystal material prepared in example 6 and the piezoelectric properties are shown in FIG. 4.
As can be seen from FIG. 4, the Nd-doped potassium sodium niobate crystal obtained by the pulling method has complete appearance, no cracking, no crack, high quality, large size, high quality single crystal, fast growth speed, and great influence of Nd doping on crystal transparency and color, and thoroughly turns into opaque light gray.
Test example 3:
the photographs of the Li-Sm co-doped and Li-Nd co-doped Li-Gd co-doped single crystals prepared in examples 9-11 and the piezoelectric properties are shown in FIG. 5, FIG. 6 and FIG. 7, respectively, and the plots are the results of the piezoelectric property test after polarization.
As can be seen from fig. 5, 6 and 7, the crystal has a complete appearance, no cracking, high quality, large size, high quality single crystal, and a fast growth rate.
The piezoelectric constants of the single crystals of Li-Sm codoped and Li-Nd codoped and Li-Gd codoped are obviously higher than those of the KNN crystal of the example 1. Therefore, the crystal prepared by the rare earth ions has excellent piezoelectric performance and shows important application prospect.
Comparative example 1
A preparation method for preparing potassium sodium niobate single crystal in China patent document CN103966659A, the size of the obtained crystal is phi 30mm multiplied by 10mm, and the growth rate is 1.2 mm/day.
Comparative example 2
Chinese patent document CN107268084A discloses a potassium sodium niobate-sodium bismuth zirconate leadless piezoelectric monocrystal and a growth method thereof, and the whole crystal obtained by the method has serious cracking.
In summary, the invention realizes the growth of KNN crystal by regulating the stoichiometric ratio between the polycrystal material and the monocrystal and by means of the melt pulling method, and provides an excellent method with large size, high quality and short time consumption of the grown crystal. In an attempt of optimizing the KNN crystal performance, rare earth element doping modification is adopted for the first time, and the crystal obtained by growth has good crystallinity, good processing performance and excellent piezoelectric performance.
Claims (10)
1. A method for quickly growing rare earth doped potassium sodium niobate monocrystal based on stoichiometric ratio components without cosolvent, wherein the molecular formula of the rare earth doped potassium sodium niobate monocrystal is (K) 1-x Na x )NbO 3 Y% molA, x is more than or equal to 0.1 and less than or equal to 0.9, Y is more than or equal to 0 and less than or equal to 5, and A is Li, la, ce, pr, nd, pm, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, sc or oxide of Y element;
the rapid growth method comprises the following steps:
(1) Selection and treatment of raw materials
a. The molecular formula (K) of the potassium sodium niobate monocrystal doped with niobium rare earth 1-x Na x )NbO 3 Chemistry of y% molAMetering ratio, weighing Na with purity of 99.99% 2 CO 3 、K 2 CO 3 And Nb (Nb) 2 O 5 Vacuum drying raw materials, and adding solid oxide or carbonate of element A during doping to obtain mixed raw materials;
b. mixing the mixed raw materials for 24-48 hours by using a mixer, enabling the mixed raw materials to be in a uniform state, pressing the mixed raw materials into a cake shape, and obtaining potassium sodium niobate polycrystal materials by adopting a solid phase sintering method;
(2) Preparation for crystal growth
a. Adding the potassium sodium niobate polycrystal material into a growth crucible in batches and in batches;
b. ultrasonically cleaning the directional seed crystal, and assembling the directional seed crystal with a seed rod after drying;
c. loading seed rods and a temperature field matched with growth into a growth furnace;
(3) Cosolvent-free melt pulling method for growing crystals
a. Heating to slowly melt the potassium sodium niobate polycrystal material, and keeping the temperature for 1-2 hours after the polycrystal material is completely melted;
b. regulating the seeding temperature, slowly lowering the potassium sodium niobate seed crystal to the surface of the melt, and carrying out neck collecting, shoulder placing and constant diameter growth;
e. after the crystal grows to the required size, slowly lifting the crystal to a position 5mm away from the liquid surface of the melt;
f. cooling to room temperature, and taking out the crystal.
2. The method according to claim 1, wherein in the step (1) a, the molecular formula (K 1-x Na x )NbO 3 -y％molA，0.3≤x≤0.7，0<y.ltoreq.2, A being an oxide of Li, nd, sm, gd, tb, yb alone or an oxide co-doped with Li and Nd, sm, gd, tb, yb.
3. The method according to claim 1, wherein in the step (1) a, the temperature of the vacuum drying is 100 to 200 ℃ and the drying time is 1 to 3 hours.
4. The method according to claim 1, wherein in the step (1) b, the sintering temperature of the solid phase sintering method for synthesizing the potassium sodium niobate polycrystal material is 800-1000 ℃ and the sintering time is 10-30 hours.
5. The method of claim 1 wherein the potassium sodium niobate seed of step (2) b employs a <100> oriented seed.
6. The method according to claim 1, wherein in step (2) a, the growth crucible is a platinum crucible, and the height and diameter of the platinum crucible are the same.
7. The method of claim 1 wherein in step (2) a, the polycrystalline material is added in an amount such that the fully melted melt exceeds 5/6 of the growth crucible volume.
8. The method according to claim 1, wherein in the step (3), the pulling rate is 0.5 to 20mm/h and the rotation speed is 8 to 20rpm at the time of crystal growth.
9. The method according to claim 1, wherein in step (3), the thermal field lateral temperature gradient is small during crystal growth, so that the solid-liquid interface temperature change is small, and in step (3), the cooling rate is 5-20 ℃/h. The slow cooling can effectively reduce the internal stress of the crystal and provide sufficient time for the ferroelectric domains to be uniformly distributed.
10. The method according to claim 1, wherein in the step (2) and the step (3), the growth atmosphere is air, and the hearth of the growth furnace is in a communication state with the outside.
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