Raw material for growth of single crystal of samarium-doped lead magnesium niobate-lead titanate and preparation method therefor

Abstract

The present application provides a raw material for the growth of a single crystal of samarium-doped lead magnesium niobate-lead titanate (Sm-PMNT), a preparation method therefor, and a single crystal. The chemical composition of the raw material for the growth of a single crystal of Sm-PMNT is SmxPb(1-1.5x)[(Mg1 / 3Nb2 / 3)0.70Ti0.30]O3, wherein 0.005 ≤ x ≤ 0.02. In the preparation method provided by the present application, millimeter-scale Sm2O3 grinding media balls are prepared, the Sm2O3 grinding media balls are used for ball milling and ball milling parameters are regulated and controlled, and a single crystal raw material for the growth of Sm-PMNT is prepared by means of two-step sintering. An appropriate amount of Sm2O3 can be uniformly doped into lead magnesium niobate-lead titanate to obtain the single crystal raw material for the growth of Sm-PMNT with uniform component distribution. By adopting the single crystal raw material for the growth of Sm-PMNT prepared by the preparation method of the present application to perform crystal growth, the quality and piezoelectric performance of the crystal can be improved.

Description

Sm-doped lead magnesium niobate-lead titanate monocrystal growth raw material and preparation method thereof

[0001] The present application claims priority to the Chinese patent application No. 202410987487.0 filed on July 23, 2024, and entitled "Sm-doped lead magnesium niobate-lead titanate monocrystal growth raw material and preparation method thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of monocrystal growth, in particular to a Sm-doped lead magnesium niobate-lead titanate monocrystal growth raw material, a preparation method thereof and a monocrystal. BACKGROUND

[0003] Ferroelectric crystal materials, especially new-type relaxor ferroelectric monocrystals represented by lead magnesium niobate-lead titanate (PMNT), have excellent electromechanical coupling performance and are widely used in many fields. Studies have shown that the performance can be optimized by rare earth doping. Among them, the piezoelectric constant of PMNT monocrystal can be improved after doping with samarium (Sm), and the piezoelectric performance is significantly improved, which has great potential in high-frequency medical imaging transducers and low-field driving actuators.

[0004] Currently, the Sm-doped PMNT raw material is mainly prepared by a two-step synthesis method: first, a magnesium niobate (MN) precursor is synthesized by a solid-phase reaction of Nb2O5 and MgO, and then reacted with TiO2, PbO and Sm2O3 to obtain a Sm-doped lead magnesium niobate-lead titanate (Sm-PMNPT) growth raw material. However, the crystal obtained by using the Sm-PMNPT growth raw material prepared by the above preparation method has higher piezoelectric performance at the bottom of the crystal rod and lower piezoelectric performance at the top of the crystal rod, and an abnormal deviation of piezoelectric performance occurs, which is due to the uneven distribution of components in the Sm-doped relaxor ferroelectric monocrystal growth raw material, resulting in poor piezoelectric performance of the crystal. Therefore, providing an effective preparation method of Sm-PMNPT growth raw material is the key to improving the quality and piezoelectric performance of the crystal.

[0005] SUMMARY

[0006] The present application aims to provide a Sm-doped lead magnesium niobate-lead titanate monocrystal growth raw material, a preparation method thereof and a monocrystal, in order to improve the problem of uneven distribution of components in the Sm-doped relaxor ferroelectric monocrystal growth raw material and improve the quality and piezoelectric performance of the crystal. The specific technical solutions are as follows:

[0007] The first aspect of the present application provides a preparation method of a Sm-doped lead magnesium niobate-lead titanate monocrystal growth raw material, wherein the chemical composition of the Sm-doped lead magnesium niobate-lead titanate monocrystal growth raw material is Sm x Pb (1-1.5x) [(Mg 1 / 3 Nb2 / 3 ) 0.70 Ti 0.30 ]O3, 0.005≤x≤0.02. The preparation method comprises the following steps:

[0008] (1) The samarium oxide powder is pressed to form a green body.

[0009] (2) The green body is subjected to gas pressure sintering to obtain a rough ball.

[0010] (3) The rough ball is processed to obtain a millimeter-level Sm2O3 milling medium ball.

[0011] (4) PbO, TiO2 and MgNb2O6 powders are weighed according to the stoichiometric ratio, mixed with the Sm2O3 milling medium ball, wet ball milling is performed to obtain a mixed powder; wherein the ball-to-material ratio is (1.2-1.6):1, the ball milling speed is 100-300 r / min, and the ball milling time is 10-24 h.

[0012] (5) The mixed powder is subjected to two-step sintering after treatment to obtain a raw material for growing a samarium-doped lead magnesium niobate lead titanate single crystal.

[0013] In some embodiments of the present application, the pressure for pressing the green body is 100-200 Mpa, and the pressure holding time for pressing the green body is 5-15 min.

[0014] In some embodiments of the present application, the sintering temperature for gas pressure sintering is 1600-1800℃, the holding time for gas pressure sintering is 2-4 hours, and the pressure for gas pressure sintering is 2-4 MPa.

[0015] In some embodiments of the present application, the diameter of the Sm2O3 milling medium ball is 2-10 mm.

[0016] In some embodiments of the present application, the Sm2O3 milling medium ball comprises large milling balls, medium milling balls and small milling balls, the diameter of the large milling balls is 8-10 mm, the diameter of the medium milling balls is 5-7 mm, and the diameter of the small milling balls is 2-4 mm.

[0017] In some embodiments of the present application, the mass ratio of the large milling balls, the medium milling balls and the small milling balls is (3-3.5):(2.5-3):1.

[0018] In some embodiments of the present application, the two-step sintering post-processing includes a first sintering and a second sintering; the first sintering process is: from room temperature, heating to 700-800℃ for 160-200 min, then heating to 800-900℃ for 340-380 min, holding for 220-260 min, then cooling to 280-320℃ for 160-200 min, and then cooling to room temperature for 220-260 min; the second sintering process is: from room temperature, heating to 800-900℃ for 160-200 min, then heating to 850-950℃ for 320-380 min, then heating to 1100-1200℃ for 340-380 min, holding for 100-140 min, then cooling to 280-320℃ for 160-200 min, and then cooling to room temperature for 220-260 min.

[0019] The second aspect of the present application provides a raw material for growing a samarium-doped lead magnesium niobate lead titanate single crystal, which is prepared according to the preparation method provided in the first aspect of the present application.

[0020] The third aspect of the present application provides a samarium-doped lead magnesium niobate lead titanate single crystal, which is prepared using the raw material for growing a samarium-doped lead magnesium niobate lead titanate single crystal provided in the second aspect of the present application.

[0021] The present application has the following beneficial effects:

[0022] The present application provides a raw material for growing a samarium-doped lead magnesium niobate lead titanate single crystal, a preparation method thereof and a single crystal, wherein the chemical composition of the raw material for growing a samarium-doped lead magnesium niobate lead titanate single crystal is Sm x Pb (1-1.5x) [(Mg 1 / 3 Nb 2 / 3 ) 0.70 Ti 0.30 ]O3, 0.005≤x≤0.02. In the preparation method provided in the present application, millimeter-level Sm2O3 grinding medium balls are prepared, the Sm2O3 grinding medium balls are used for ball milling and the ball milling parameters are regulated, and a single crystal raw material for growing Sm-PMNT is prepared through two-step sintering post-processing, so that an appropriate amount of Sm2O3 can be uniformly doped in lead magnesium niobate lead titanate, and a single crystal raw material for growing Sm-PMNT with uniform component distribution is obtained. The single crystal raw material for growing Sm-PMNT prepared by the preparation method of the present application can be used for single crystal growth, which can improve the abnormal deviation of the piezoelectric properties of the crystal and improve the piezoelectric properties of the crystal.

[0023] Of course, implementing any product or method of the present application does not necessarily require achieving all the advantages described above at the same time. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments of the present application. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0025] The Sm-PMNPT crystal prepared by the two-step synthesis method in the prior art has the following problems: in the piezoelectric performance test of the crystal, the piezoelectric performance of the bottom of the crystal rod is higher, and the piezoelectric performance of the top of the crystal rod is lower, and an abnormal deviation of the piezoelectric performance occurs. The inventors find that this is mainly due to the fact that the dopant samarium oxide cannot be uniformly doped into PMNT, resulting in enrichment of the samarium oxide concentration, causing the composition of the Sm-PMNPT growth raw material to be non-uniform, thereby leading to poor crystal quality and poor piezoelectric performance.

[0026] Therefore, the first aspect of the present application provides a preparation method of a raw material for growing a samarium-doped lead magnesium niobate lead titanate single crystal, wherein the chemical composition of the raw material for growing the samarium-doped lead magnesium niobate lead titanate single crystal is Sm x Pb (1-1.5x) [(Mg 1 / 3 Nb 2 / 3 ) 0.70 Ti 0.30 ]O3, 0.005≤x≤0.02, for example, the value of x can be 0.005, 0.006, 0.008, 0.01, 0.02, 0.15, 0.17, 0.02, or a range composed of any two of the above values. The preparation method comprises the following steps:

[0027] (1) The samarium oxide powder is pressed to form a green body.

[0028] (2) The green body is subjected to gas pressure sintering to obtain a blank ball.

[0029] (3) The blank ball is processed to obtain a millimeter-level Sm2O3 grinding medium ball.

[0030] (4) The PbO, TiO2 and MgNb2O6 powders are weighed according to the stoichiometric ratio, mixed with the Sm2O3 grinding medium ball, and subjected to wet ball milling to obtain a mixed powder.

[0031] (5) The mixed powder is subjected to two-step sintering post-processing to obtain the raw material for growing the samarium-doped lead magnesium niobate lead titanate single crystal.

[0032] The chemical composition of the raw material for growing the samarium-doped lead magnesium niobate lead titanate single crystal is shown above. The inventors have found that when the value of x is too small or too large, a single crystal raw material with uniform component distribution for growing Sm-PMNT cannot be obtained, which is not conducive to improving the performance of the crystal. Therefore, controlling the value of x within the above range is conducive to obtaining a single crystal raw material with uniform component distribution for growing Sm-PMNT, thereby improving the piezoelectric properties of the crystal.

[0033] In the present application, the ball-to-material ratio of wet ball milling is (1.2-1.6):1, the rotation speed of ball milling is 100-300 r / min, and the ball milling time is 10-24 h. For example, the ball-to-material ratio of wet ball milling can be 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, or a range formed by any two of the above values, the rotation speed of ball milling can be 100 r / min, 120 r / min, 150 r / min, 180 r / min, 200 r / min, 230 r / min, 250 r / min, 300 r / min, or a range formed by any two of the above values, and the ball milling time can be 10 h, 12 h, 15 h, 17 h, 20 h, 22 h, 24 h, or a range formed by any two of the above values. When the ball-to-material ratio is too small, for example, less than 1.2:1, the ball milling efficiency is poor and the powder mixture is not uniform; when the ball-to-material ratio is too large, greater than 1.6:1, the powder ball milling efficiency is reduced, and the powder mixture is also not uniform. By controlling the above parameters within the range of the present application, it is beneficial to incorporate Sm2O3 with a target content in lead magnesium niobate lead titanate (PMNT), which can uniformly incorporate Sm2O3 in PMNT, improve the problem of component deviation and non-uniformity of the Sm-PMNPT growth raw material caused by the enrichment of samarium oxide concentration, and thus improve the quality and piezoelectric properties of the crystal.

[0034] In the preparation method provided in the present application, millimeter-sized Sm2O3 grinding medium balls are prepared, Sm2O3 grinding medium balls are used for ball milling and the ball milling parameters are controlled, and a single crystal raw material for growing Sm-PMNT is prepared after two-step sintering and post-processing, which can uniformly incorporate Sm2O3 with a target content in PMNT and obtain a single crystal raw material for growing Sm-PMNT with uniform component distribution. The single crystal raw material for growing Sm-PMNT prepared by the preparation method of the present application can be used for single crystal growth, which can improve the quality and piezoelectric properties of the crystal.

[0035] In the present application, the step (1) can further include a pretreatment step of the samarium oxide powder, which can include but is not limited to: adding a binder to the samarium oxide to granulate, and then sieving to obtain the samarium oxide powder. The binder can be a polyvinyl alcohol (PVA) aqueous solution binder, the mass percentage of polyvinyl alcohol in the polyvinyl alcohol aqueous solution binder is 5%-12%, and the mass percentage of the binder in the samarium oxide powder is 1%-3%.

[0036] In the present application, after the samarium oxide powder is pressed to form a green body to obtain a green ball, a degassing process can be further included, which is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the degassing process can be performed by keeping the green ball at 600-650°C for 6-12h to remove the binder in the green ball.

[0037] In some embodiments of the present application, the pressure for pressing the green body is 100-200Mpa, and the holding time for pressing the green body is 5-15min. For example, the pressure for pressing the green body can be 100Mpa, 120MPa, 150Mpa, 160Mpa, 180Mpa, 200Mpa, or a range formed by any two of the above values, and the holding time for pressing the green body can be 5min, 7min, 10min, 11min, 12min, 13min, 15min, or a range formed by any two of the above values. By adjusting the pressure and holding time for pressing the green body within the above ranges, the green ball can be better shaped to obtain high-quality samarium oxide grinding media balls, so that the Sm-PMNT single crystal raw material with uniform component distribution can be obtained.

[0038] In some embodiments of the present application, the sintering temperature for gas pressure sintering is 1600-1800°C, the holding time for gas pressure sintering is 2-4h, and the pressure for gas pressure sintering is 2-4MPa. For example, the sintering temperature for gas pressure sintering can be 1600°C, 1650°C, 1700°C, 1750°C, 1800°C, or a range formed by any two of the above values, the holding time for gas pressure sintering can be 2h, 2.5h, 3h, 3.5h, 4h, or a range formed by any two of the above values, and the pressure for gas pressure sintering can be 2MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa, or a range formed by any two of the above values. By adjusting the sintering temperature, holding time, and pressure for gas pressure sintering within the above ranges, the density of the samarium oxide grinding media ball can be improved, high-quality samarium oxide grinding media balls can be obtained, and thus the Sm-PMNT single crystal raw material with uniform component distribution can be obtained.

[0039] In some embodiments of the present application, the diameter of the Sm2O3 milling medium balls is 2-10 mm. For example, the diameter of the Sm2O3 milling medium balls can be 2 mm, 4 mm, 5 mm, 6 mm, 8 mm, 10 mm, or a range defined by any two of the aforementioned values. By adjusting the diameter of the Sm2O3 milling medium balls within the aforementioned range, the ball milling of the mixture is more uniform, and thus a single crystal raw material for Sm-PMNT growth with uniform component distribution can be obtained.

[0040] In some embodiments of the present application, the Sm2O3 milling medium balls include large milling medium balls, medium milling medium balls, and small milling medium balls. The diameter of the large milling medium balls is 8-10 mm, the diameter of the medium milling medium balls is 5-7 mm, and the diameter of the small milling medium balls is 2-4 mm. For example, the diameter of the large milling medium balls can be 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, or a range defined by any two of the aforementioned values, the diameter of the medium milling medium balls can be 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, or a range defined by any two of the aforementioned values, and the diameter of the small milling medium balls can be 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, or a range defined by any two of the aforementioned values. By adjusting the diameter of the large milling medium balls, the medium milling medium balls, and the small milling medium balls within the aforementioned ranges, the ball milling of the mixture is more uniform, and thus a single crystal raw material for Sm-PMNT growth with uniform component distribution can be obtained, the abnormal deviation of the piezoelectric properties of the crystal is improved, and thus the quality and piezoelectric properties of the crystal are improved.

[0041] In some embodiments of the present application, the mass ratio of the large milling medium balls, the medium milling medium balls, and the small milling medium balls is (3-3.5):(2.5-3):1. For example, the mass ratio of the large milling medium balls, the medium milling medium balls, and the small milling medium balls can be 3.3:2.5:1, 3:3:1, 3:2.6:1, 3.1:2.9:1, 3:2.8:1, 3.4:2.9:1, or a range defined by any two of the aforementioned values. By adjusting the mass ratio of the large milling medium balls, the medium milling medium balls, and the small milling medium balls within the aforementioned range, the ball milling efficiency is improved, the energy consumption and local excessive wear of the milling medium balls during the ball milling process are reduced, and the quality and uniformity of the Sm2O3 are improved, and thus a single crystal raw material for Sm-PMNT growth with uniform component distribution can be obtained, the abnormal deviation of the piezoelectric properties of the crystal is improved, and thus the quality and piezoelectric properties of the crystal are improved.

[0042] In some embodiments of the present application, the two-step sintering post-processing includes a first sintering and a second sintering; the first sintering process is: from room temperature, increasing the temperature to T1 = 700-800℃ for 160-200 min, then increasing the temperature to T2 = 800-900℃ for 340-380 min, keeping the temperature for 220-260 min, then decreasing the temperature to 280-320℃ for 160-200 min, and then decreasing to room temperature for 220-260 min; the second sintering process is: from room temperature, increasing the temperature to T3 = 800-900℃ for 160-200 min, then increasing the temperature to T4 = 850-950℃ for 320-380 min, then increasing the temperature to T5 = 1100-1200℃ for 340-380 min, keeping the temperature for 100-140 min, then decreasing the temperature to 280-320℃ for 160-200 min, and then decreasing to room temperature for 220-260 min. For example, T1 can be 700℃, 720℃, 750℃, 770℃, 800℃, or a range formed by any two of the above values, T2 can be 800℃, 820℃, 850℃, 870℃, 900℃, or a range formed by any two of the above values, T3 can be 800℃, 820℃, 850℃, 870℃, 900℃, or a range formed by any two of the above values, T4 can be 850℃, 870℃, 900℃, 920℃, 950℃, or a range formed by any two of the above values, and T5 can be 1100℃, 1120℃, 1150℃, 1170℃, 1200℃, or a range formed by any two of the above values. By using the above two-step sintering post-processing process, the solid-phase reaction between PbO, TiO2, MgNb2O6 and Sm2O3 can be more sufficient, so that a Sm-PMNT single crystal raw material with uniform component distribution can be obtained.

[0043] In the present application, the pressing forming is not particularly limited as long as the purpose of the present application can be achieved. For example, a ball making mold can be used to put into a cold isostatic press for ball pressing to obtain a green ball. The present application does not particularly limit the ball making mold, and those skilled in the art can design and select according to actual needs as long as the purpose of the present application can be achieved.

[0044] In the present application, the atmosphere for gas pressure sintering is not particularly limited as long as the purpose of the present application can be achieved, for example, gas pressure sintering can be carried out in an argon atmosphere.

[0045] In the present application, the process of processing the blank ball into the grinding medium ball is not particularly limited as long as the purpose of the present application can be achieved, for example, the blank ball can be processed by grinding, specifically, the blank ball is coarsely ground and finely ground by using a disc grinder in the grinding process, so that a millimeter-level Sm2O3 grinding medium ball is obtained. Generally, when the Sm2O3 grinding medium ball is prepared according to the above process, the diameter of the Sm2O3 grinding medium ball can be controlled by adjusting the grinding time, grinding speed, grinding medium and the like. The present application does not have a particular limitation, and those skilled in the art can adjust according to the actual needs as long as the purpose of the present application can be achieved.

[0046] In the present application, the PbO, TiO2, and MgNb2O6 powders are preferably high-purity powders with a purity of 99.99%. The solvent for wet ball milling is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, alcohol can be used as the solvent for wet ball milling.

[0047] The equipment used for the two-step sintering post-processing is not particularly limited in the present application as long as the purpose of the present application can be achieved, for example, the mixed powder can be placed in a corundum crucible, sealed with a cover, and then put into a box-type electric furnace for the first sintering and the second sintering treatment.

[0048] The second aspect of the present application provides a raw material for growing a Sm-doped lead magnesium niobate-lead titanate single crystal, which is prepared according to the preparation method provided in the first aspect of the present application, so that the components of the Sm-PMNPT growth raw material are uniform.

[0049] The third aspect of the present application is a Sm-doped lead magnesium niobate-lead titanate single crystal, which is prepared by using the Sm-doped lead magnesium niobate-lead titanate single crystal growth raw material provided in the second aspect of the present application. The Sm-PMNPT single crystal growth raw material provided in the second aspect of the present application has uniform components, so that the Sm-PMNPT single crystal prepared by using it has high quality and good piezoelectric properties, and the problem of abnormal deviation of piezoelectric properties is improved.

[0050] In the present application, the above-mentioned Sm-doped lead magnesium niobate-lead titanate single crystal is prepared by the crucible lowering method, and the present application does not have a particular limitation as long as the purpose of the present application can be achieved.

[0051] Examples

[0052] Hereinafter, examples and comparative examples are given to more specifically explain the embodiments of the present application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are mass-based.

[0053] Test methods and equipment:

[0054] Inductively coupled plasma emission spectrometry test:

[0055] The Sm-PMNT single crystal raw material prepared in the examples and the comparative examples was tested by inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7700) at room temperature. The Sm-PMNT single crystal raw material prepared in each of the examples and the comparative examples was sampled randomly from three different positions in the crucible, labeled as A, B and C, and subjected to inductively coupled plasma emission spectrometry to obtain the content of each element and deduce the chemical composition of the Sm-PMNT single crystal raw material.

[0056] Piezoelectric test:

[0057] The Sm-PMNT or PMNT single crystal raw material prepared in each of the examples and the comparative examples was placed in a platinum crucible, which was placed in a crystal growth furnace, and the crystal was grown by the crucible lowering method at a temperature of 1300°C and a lowering rate of 20 mm / day to obtain a Sm-PMNT relaxor ferroelectric crystal with a sample size of 5.59 cm in diameter and 12 cm in length. The piezoelectric constant d 33 of the bottom of the crystal was measured by a ZJ-4AN type quasi-static d 33 meter, and the piezoelectric constant d 33 of the top of the crystal was measured by a ZJ-4AN type quasi-static d 0.01 meter. The upper end of the crystal taken out of the crystal growth furnace was the top of the crystal, and the lower end was the bottom of the crystal. The sampling position of the top of the crystal was 1 cm from the upper end, and the sampling position of the bottom of the crystal was 1 cm from the lower end.

[0058] The greater the increase in the piezoelectric constant of the top and bottom of the crystal compared to the PMNT without Sm doping, the better the piezoelectric performance. The decrease in the piezoelectric constant of the top and bottom of the crystal indicates that the piezoelectric performance is deteriorating. The abnormal deviation of the piezoelectric constant of the top and bottom of the crystal also indicates that the piezoelectric performance is poor. Generally, the piezoelectric constant of the bottom of the crystal is lower than that of the top of the crystal without Sm doping. When Sm is doped, if the piezoelectric constant of the bottom of the crystal is higher than that of the top of the crystal, it is considered that there is an abnormal deviation problem of piezoelectric performance. The greater the difference between the piezoelectric constant of the bottom of the crystal and that of the top of the crystal, the more obvious the problem of abnormal deviation of piezoelectric performance.

[0059] Example 1

[0060] The chemical composition of the Sm 0.01 Pb 0.985 [(Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 ]O3 relaxor ferroelectric single crystal growth raw material (i.e. Sm-PMNT single crystal raw material) preparation method comprises the following steps:

[0061] (1) Add 8% by mass of polyvinyl alcohol (PVA) aqueous solution binder to the samarium oxide powder, granulate, and sieve through a 50-mesh standard sieve. The mass percentage of the binder is 1% based on the mass of the samarium oxide powder. Then, the sieved samarium oxide powder is loaded into spherical molding molds with diameters of 3 mm, 9 mm, and 15 mm, respectively, and is placed into a cold isostatic press to perform spherical molding, to obtain small grinding ball preforms, medium grinding ball preforms, and large grinding ball preforms. The molding pressure is 120 MPa, 160 MPa, and 180 MPa, respectively, and the pressure holding time is 5 min, 8 min, and 10 min, respectively. Then, the preforms are placed into a box-type electric furnace for degassing treatment at 650°C for 10 h.

[0062] (2) The preforms obtained in step (1) are placed into an argon atmosphere pressure sintering furnace for pressure sintering, to obtain rough grinding balls. The sintering temperature is 1700°C, the pressure is 3 MPa, and the holding time is 2 h.

[0063] (3) The rough grinding balls obtained above are subjected to two-step processing of rough grinding and fine grinding, to obtain small grinding balls with a diameter of 2 mm, medium grinding balls with a diameter of 6 mm, and large grinding balls with a diameter of 10 mm, i.e., millimeter-level Sm2O3 grinding medium balls.

[0064] (4) High-purity (purity of 99.99%) powdered MgNb2O6, PbO, and TiO2 are weighed and mixed according to stoichiometric ratios, and then the Sm2O3 grinding medium balls obtained in the above step and alcohol are added, wet ball milling is performed, a slurry is prepared, and the slurry is dried, to obtain a mixed powder. The Sm2O3 grinding medium balls used include the large grinding balls, the medium grinding balls, and the small grinding balls prepared above, and the mass ratio of the large grinding balls, the medium grinding balls, and the small grinding balls is 3.3:2.5:1, the ball-to-material ratio is 1.5:1, the ball milling speed is 190 r / min, and the time is 18 h.

[0065] (5) The mixed powder is placed in a corundum crucible, which is tightly sealed, and is placed into a box-type electric furnace, which is heated from room temperature to T1=750°C over 180 min, then heated to T2=850°C over 360 min, held at T2=850°C for 240 min, then cooled to 300°C over 180 min, and then cooled to room temperature over 240 min.

[0066] (6) The sintered material of step (5) is subjected to a second sintering, which is heated from room temperature to T3=850°C over 180 min, then heated to T4=900°C over 360 min, then heated to T5=1100°C over 360 min, held at T5=1100°C for 120 min, then cooled to 300°C over 180 min, and then cooled to room temperature over 240 min, to obtain Sm-PMNT single crystal growth raw material.

[0067] Examples 2 to 7

[0068] The rest is the same as Example 1 except that the parameters are adjusted according to Table 1.

[0069] Example 8

[0070] The rest is the same as Example 1 except that only medium grinding balls with a diameter of 6 mm are used during wet ball milling.

[0071] Comparative Example 1

[0072] The chemical composition of Sm 0.01 Pb 0.985 [(Mg 1 / 3 Nb 2 / 3 ) 0.7 Ti 0.3 ]O3 is prepared by the following method, which comprises the following steps:

[0073] (1) High-purity powdered MgO and Nb2O5 are mixed according to stoichiometric proportions, sintered at 1200°C for 6h to synthesize a precursor MgNb2O6.

[0074] (2) High-purity powdered Sm2O3, PbO, TiO2, and the above-prepared precursor MgNb2O6 are mixed according to stoichiometric proportions, and the above raw materials are mixed through a 16-mesh sieve, twice, to obtain the initial raw materials.

[0075] (3) The initial raw materials are placed in a crucible, covered and sealed, and placed in a high-temperature block furnace, and heated from room temperature to 750°C over 180 min, then heated to 850°C over 360 min, and then heated to 300°C over 180 min, and then cooled to room temperature over 240 min, to obtain a sintered material.

[0076] (4) The sintered material is heated from room temperature to 850°C over 180 min, then heated to 900°C over 360 min, then heated to 1100°C over 360 min, and then heated to 300°C over 180 min, and then cooled to room temperature over 240 min, to obtain a sintered material.

[0077] Comparative Example 2

[0078] The chemical composition of 0.67[Pb(Mg 1 / 3 Nb 2 / 3 )O3]-0.33(PbTiO3) is prepared by the following method, which comprises the following steps:

[0079] (1) High-purity powdery MgNb2O6, PbO and TiO2 are weighed and mixed according to stoichiometric ratio, zirconia grinding medium balls and alcohol are added, wet ball milling is performed to mix the materials, the slurry is obtained, and the slurry is dried to obtain the mixed powder. The zirconia grinding medium balls include large grinding balls with a diameter of 10 mm, medium grinding balls with a diameter of 6 mm and small grinding balls with a diameter of 2 mm, the mass ratio of the large grinding balls, the medium grinding balls and the small grinding balls is 3:3:1, the ball-to-material ratio is 1.5:1, the ball milling speed is 150 r / min, and the time is 18 h.

[0080] (2) The mixed powder is placed in a corundum crucible, the crucible is tightly covered, and the crucible is placed in a box-type electric furnace, the temperature is raised from room temperature to T1=800℃ for 180 min, then the temperature is raised to T2=850℃ for 360 min, the temperature is kept for 240 min, then the temperature is lowered to 300℃ for 180 min, and then the temperature is lowered to room temperature for 240 min.

[0081] (3) The sintered material in step (2) is subjected to second sintering, the temperature is raised from room temperature to T3=850℃ for 180 min, then the temperature is raised to T4=900℃ for 360 min, then the temperature is raised to T5=1150℃ for 360 min, the temperature is kept for 120 min, then the temperature is lowered to 300℃ for 180 min, and then the temperature is lowered to room temperature for 240 min, to obtain the single crystal raw material for PMNT growth.

[0082] The related parameters of each example and the comparative example are shown in Table 1 and Table 2.

[0083] Table 1 Note: " / " in Table 1 indicates that the corresponding parameter does not exist.

[0084] Table 2 Note: " / " in Table 2 indicates that the corresponding parameter does not exist.

[0085] As can be seen from Examples 1 to 8 and Comparative Examples 1 to 2, in the Sm-PMNT single crystal raw material prepared by the preparation method provided in the present application, the relative error between the measured value and the target value of the mass percentage of Sm element is small, and in particular, in Examples 1 to 7, the relative error between the measured value and the target value of the mass percentage of Sm element is less than 10%; and the measured values of the mass percentage of Sm element at different A, B and C points are relatively close. It is shown that in the preparation method, the high-efficiency doping of the samarium oxide by ball milling is realized, so that the actual chemical composition of the Sm element component in the Sm-PMNT single crystal raw material is highly consistent with the pre-designed chemical composition, the overall uniformity of the powder is significantly improved, which is helpful for the growth of high-quality Sm-PMNT relaxor ferroelectric single crystal, so that the piezoelectric constants of the bottom and the top of the crystal are relatively close. In the Sm-PMNT single crystal raw material prepared by the traditional synthesis method used in Comparative Example 1, there is a significant difference between the mass percentage of Sm element and the target value, and the average value of the relative error of the mass percentage of Sm element is as high as 61.814%, and the measured values of the mass percentage of Sm element at different A, B and C points are quite different, which shows that the uniformity of the Sm-PMNT single crystal raw material powder prepared by this method is very poor. Compared with Comparative Example 2, the piezoelectric constant of the bottom of the crystal of Comparative Example 1 is greatly improved, while the piezoelectric constant of the top of the crystal is reduced, and the difference between the piezoelectric constant of the bottom and the top of the crystal is too large, and there is a significant abnormal deviation problem of piezoelectric performance. Compared with Comparative Example 2, the piezoelectric constant of the bottom and the top of the crystal of Example 8 is improved, in which the piezoelectric constant of the bottom is improved more, and the piezoelectric constant of the top is improved less, and there is a slight abnormal deviation problem of piezoelectric performance, but the relative error between the measured value and the target value of the mass percentage of Sm element is smaller than that of Comparative Example 1, and the difference between the piezoelectric constant of the top and the bottom is also smaller than that of Comparative Example 1, which shows that compared with Comparative Example 1, the abnormal deviation problem of piezoelectric performance of the crystal in Example 8 is improved.

[0086] The preparation method provided in the present application can effectively reduce the deviation of the Sm element component in the Sm-PMNT single crystal raw material, so that the composition of the actually prepared Sm-PMNT single crystal raw material is highly consistent with the original designed chemical composition, thereby being conducive to the growth of Sm-PMNT relaxor ferroelectric single crystal and improving the quality and piezoelectric performance of the crystal.

[0087] It is to be noted that, in the present document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0088] Each of the embodiments in the present specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other. Each of the embodiments focuses on the difference from other embodiments.

[0089] The above only describes the preferred embodiments of the present application, and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing raw materials for the growth of samarium-doped lead magnesium niobate and lead titanate single crystals, wherein, The chemical composition of a raw material for growing the samarium-doped titanium niobium magnesium lead acid lead single crystal is Sm x Pb (1-1.5x) [(Mg 1 / 3 Nb 2 / 3 ) 0.70 Ti 0.30 ]O3, 0.005≤x≤0.02; The preparation method comprises the following steps: (1) forming a green body by pressing and molding a samarium oxide powder; (2) obtaining a rough ball by pressure sintering the green body; (3) obtaining a millimeter-level Sm2O3 milling medium ball by processing the rough ball; (4) obtaining a mixed powder by mixing Sm2O3 milling medium balls with PbO, TiO2 and MgNb2O6 powders in a stoichiometric ratio through wet ball milling, wherein the ball-to-material ratio is (1.2-1.6):1, the rotation speed of the ball mill is 100-300 r / min, and the ball milling time is 10-24 h; (5) obtaining the raw material for growing a samarium-doped lead magnesium niobate lead titanate single crystal by two-step sintering post-processing of the mixed powder.

2. The production method according to claim 1, wherein, The pressure for the pressing and molding is 100-200 MPa, and the pressure holding time for the pressing and molding is 5-15 min.

3. The production method according to claim 1, wherein The sintering temperature for the pressure sintering is 1600-1800 ℃, the holding time for the pressure sintering is 2-4 h, and the pressure for the pressure sintering is 2-4 MPa.

4. The production method according to claim 1, wherein The diameter of the Sm2O3 milling medium ball is 2-10 mm.

5. The production method according to claim 1, wherein The Sm2O3 milling medium ball comprises large milling balls, medium milling balls and small milling balls, the diameter of the large milling balls is 8-10 mm, the diameter of the medium milling balls is 5-7 mm, and the diameter of the small milling balls is 2-4 mm.

6. The production method according to claim 5, wherein The mass ratio of the large milling balls, the medium milling balls and the small milling balls is (3-3.5):(2.5-3):

1.

7. The production method according to claim 1, wherein The two-step sintering post-processing comprises first sintering and second sintering. The first sintering process is: increasing the temperature from room temperature to 700-800 ℃ in 160-200 min, then increasing the temperature to 800-900 ℃ in 340-380 min, holding the temperature for 220-260 min, then decreasing the temperature to 280-320 ℃ in 160-200 min, and then decreasing the temperature to room temperature in 220-260 min; The second sintering process is: increasing the temperature from room temperature to 800-900 ℃ in 160-200 min, then increasing the temperature to 850-950 ℃ in 320-380 min, then increasing the temperature to 1100-1200 ℃ in 340-380 min, holding the temperature for 100-140 min, then decreasing the temperature to 280-320 ℃ in 160-200 min, and then decreasing the temperature to room temperature in 220-260 min.

8. A raw material for growing a samarium-doped lead magnesium niobate lead titanate single crystal, which is prepared according to the preparation method in any one of claims 1 to 7.

9. A samarium-doped lead magnesium niobate lead titanate single crystal, which is prepared by using the raw material for growing a samarium-doped lead magnesium niobate lead titanate single crystal in claim 8.

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