Sodium bismuth titanate-based ceramic material with large monopole electrostrictive strain and preparation method thereof

Abstract

The invention discloses a sodium bismuth titanate-based ceramic material with large monopole electrostrictive strain and a preparation method of the sodium bismuth titanate-based ceramic material, and relates to the field of lead-free electrostrictive ceramics. The lead-free electrostrictive ceramic material comprises the following raw material components in mole percentage: [a (Bi0. 5Na0. 5TiO3)-b (BaTiO3)]-xMn-yR, R is a rare earth element, a is equal to 0.90-0.98, b is equal to 0.02-0.1, a + b is equal to 1, x is the doping amount of Mn and is 0.1%-3% in mole percentage, y is the doping amount of R and is 0.1%-3% in mole percentage, and the lead-free electrostrictive ceramic with high density and large unipolar electrostrictive strain is prepared and synthesized by adopting a traditional solid-phase reaction method. Wherein the maximum value of the electrostrictive strain of the Sm-doped ceramic is 1.92% under the action of an electric field of 5.5 kV / mm at the temperature of 80 DEG C, and the maximum value of the electrostrictive strain of the La-doped ceramic is 2.63% under the action of the electric field of 6.5 kV / mm at the temperature of 80 DEG C. The invention has the advantages of simple components and process steps, easiness in operation and good repeatability, and can be applied to transducers, micro-displacers and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lead-free electrostrictive ceramics, further to the field of lead-free electrostrictive ceramics based on perovskite-type sodium bismuth titanate, in particular to a sodium bismuth titanate-based ceramic material with large unipolar electrostrictive strain and a preparation method thereof. BACKGROUND

[0002] Piezoelectric actuators have the advantages of large output displacement, high sensitivity, and resistance to electromagnetic interference, and have been widely used as a micro-displacement device with great development potential. Piezoelectric materials are the core components of piezoelectric actuators, and the electric field-induced strain (electric strain) behavior of piezoelectric materials is a key factor in determining the performance of the actuator. Traditional electrostrictive materials are mainly lead-based relaxor ferroelectric materials, such as Pb(Mg 1 / 3 Nb2 / 3 )O3(PMN), Pb(Zn 1 / 3 Nb 2 / 3 )O3(PZN) and other materials, with the highest reported electric strain of 1.3%. In addition, lead is restricted by the Restriction of Hazardous Substances (RoHS) directive and the Waste Electrical and Electronic Equipment (WEEE) directive due to its toxicity and environmental damage. Therefore, it is a key requirement for actuation applications to achieve greater electric strain in piezoelectric materials, especially in lead-free materials.

[0003] Currently, in the research of lead-free electrostrictive ceramics, three types of lead-free ceramics with perovskite structure, namely BaTiO3(BT) system, K 0.5 Na 0.5 NbO3(KNN) system and Bi 0.5 Na 0.5 TiO3(BNT) system, have been widely studied due to their excellent electrical properties and the possibility of large-scale production using traditional preparation processes. Among them, BNT-based lead-free ceramics have attracted much attention due to their relatively superior electrical properties, especially in the morphotropic phase boundary (MPB), a(Bi 0.5 Na 0.5 TiO3)-b(BaTiO3)(BNBT)(where a=0.90-0.98, b=0.02-0.1) has a high piezoelectric response (d 33 ), a suitable coercive field (E c) and high power performance, which provides superior electrostriction for piezoelectric actuators. It is considered as one of the most promising lead-free ceramic systems to replace lead-based electrostrictive ceramics. So far, the maximum unipolar electrostriction reported in lead-free polycrystalline piezoelectric ceramics is less than 1.6%. But the performance of pure component BNBT ceramic lead-free electrostrictive ceramics has not yet reached the requirements for completely replacing lead-based electrostrictive ceramics, which poses a severe challenge to the research of lead-free electrostrictive ceramics. Therefore, how to further improve the unipolar electrostrictive strain of BNBT-based ceramics has become a key problem to be solved in the field of lead-free electrostrictive ceramics. SUMMARY

[0004] In view of the defects that the existing pure BNBT ceramic electrostriction is insufficient and difficult to replace lead-based materials, the purpose of the present application is to provide a large unipolar electrostrictive strain sodium bismuth titanate ceramic material and a preparation method thereof. By simultaneously doping rare earth elements (La or Sm) at A site and Mn elements at B site, A site vacancies and oxygen vacancies are introduced and defect dipoles are formed. After applying a positive electric field, the dipoles are stretched, which induces a large unipolar strain near the phase transition point. The sodium bismuth titanate ceramic prepared by the present application has a S-y of 80 o C and an electric field of 5.5 kV / mm, the maximum strain value of the electrostriction is 1.92%, and when the doped rare earth element is La, L-y is 80 o C and an electric field of 6.5 kV / mm, the maximum strain value of the electrostriction is 2.63%, and the relaxor phase and ferroelectric phase realize reversible conversion under external field excitation.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a large unipolar electrostrictive strain sodium bismuth titanate ceramic material, the chemical general formula of the matrix is a(Bi 0.5 Na 0.5 TiO3)-b(BaTiO3), which is obtained by simultaneously doping rare earth elements (La or Sm) at A site and Mn elements at B site.

[0006] The raw material components and their molar percentage contents of the sodium bismuth titanate ceramic material are [a(Bi 0.5 Na 0.5 TiO3)-b(BaTiO3)]-xMn-yR, R is a rare earth element, wherein a=0.90-0.98, b=0.02-0.1, a+b=1, x is the doping amount of Mn, which is 0.1%-3% in terms of molar percentage, and y is the doping amount of R, which is 0.1%-3% in terms of molar percentage.

[0007] Preferably, a = 0.95, b = 0.05, x = 0.5%, y = 1.0-2.0%, R is selected from La, Sm, when R is selected from La, the sodium bismuth titanate-based ceramic material is abbreviated as L-y, and when R is selected from Sm, the sodium bismuth titanate-based ceramic material is abbreviated as S-y.

[0008] The electrostrictive ceramic described in the application has a high strain value and has a very important application prospect in the fields of sensors and displacers.

[0009] The second aspect of the application provides a preparation method of the above-mentioned large single-pole electrostrictive strain sodium bismuth titanate-based ceramic material, which is prepared by a solid-phase synthesis method and comprises the following steps: (1) ingredient synthesis The raw materials Bi2O3 (Aladdin, 99.99%), Na2CO3 (Aladdin, 99.5%), BaCO3 (Aladdin, 99.95%), TiO2 (Aladdin, 99.8%), an oxide of R, and MnO2 (Aladdin, 99%) are weighed according to the above-mentioned molar ratio of raw material components, loaded into a ball mill jar, ball milled, dried, ground, and sieved; wherein the raw material is La2O3 (Aladdin, 99.9%) when R is La, and the raw material is Sm2O3 (Aladdin, 99.9%) when R is Sm; (2) pre-sintering The mixed powder in step (1) is placed in a muffle furnace, pre-sintered at 700-950 o C, heat preserved for 3-8 h, naturally cooled to room temperature, and pre-sintered powder is obtained; (3) secondary ball milling The pre-sintered powder in step (2) is ground, sieved, ball milled, and dried to obtain a ball milled powder; (4) granulation The ball milled powder dried in step (3) is finely ground and sieved, and then fully mixed and stirred with polyvinyl alcohol (PVA) or distilled water, sieved to obtain a granulated powder; (5) forming The granulated powder in step (4) is pressed and formed into a cylindrical blank under a pressure of not less than 100 MPa; (6) sintering The blank in step (5) is placed in a muffle furnace, heated at a rate of 3 °C / min to 1050 °C-1250 °C for sintering, heat preserved for 2-6 h, and naturally cooled to room temperature with the furnace to obtain a sintered sample; (7) burning electrodes The sintered sample in step (6) is polished, the upper and lower surfaces are coated with silver paste, and is placed in a muffle furnace and heat treated at 500-600 o C for 0.5-1 h to obtain the sodium bismuth titanate-based ceramic material.

[0010] The dielectric and electrostrictive properties of the sodium bismuth titanate-based ceramic material sample are subsequently tested.

[0011] Preferably, in step (1), the ball milling tank is a nylon tank, the ball milling medium is anhydrous ethanol and zirconium balls, the mass ratio of zirconium balls: mixed powder: anhydrous ethanol is 2:1:1-4, the ball milling speed is 300-500 r / min, the ball milling time is 6-14 h, the drying temperature is 70-100 o C.

[0012] Preferably, in step (2), the mixed powder is placed in a corundum crucible for compaction and pre-sintering in a Bi2O3 atmosphere in a muffle furnace.

[0013] Preferably, in step (4), polyvinyl alcohol (PVA) or distilled water is uniformly mixed with the ball milled powder, wherein the mass percentage of polyvinyl alcohol (PVA) or distilled water in the whole is 3-8%, and both times of sieving use 100 mesh sieves.

[0014] It should be noted that if the polyvinyl alcohol aqueous solution is less than 3%, the sample is not easy to shape and the electrostrictive ceramic material cannot be obtained; if it is higher than 8%, the sample has holes and a dense electrostrictive ceramic material cannot be obtained. The content of the polyvinyl alcohol aqueous solution is preferably 5%.

[0015] Preferably, in step (5), the cylinder-shaped blank is pressed under a pressure of not less than 100 Mpa and pressure holding treatment is performed.

[0016] Preferably, in step (6), the sintering (without burying) is performed by placing in a muffle furnace, heating to 1050-1250 °C at a rate of 3 °C / min, holding for 2-6 h, and naturally cooling to room temperature with the furnace, and all heating rates are <5 o C / min.

[0017] Preferably, in step (7), the thickness of the sintered sample is polished to 300-500 μm.

[0018] The large single-pole electrostrictive sodium bismuth titanate-based ceramic prepared by the method has a S-y of 80 o C and a maximum strain value of 1.92% under the action of an electric field of 5.5 kV / mm.

[0019] The prepared large unipolar electro-strained sodium bismuth titanate ceramic has L-y of 80 o The maximum strain value of the electro-strain under the action of C and electric field 6.5 kV / mm is 2.63%.

[0020] Compared with the prior art, the application has the following beneficial effects: 1. The traditional solid-phase synthesis method is adopted to prepare the sodium bismuth titanate ceramic. 0.5 Na 0.5 TiO3)-b(BaTiO3)] (wherein a=0.90-0.98, b=0.02-0.1) (BNBT) as the matrix, A-site vacancies and oxygen vacancies are introduced by simultaneously doping rare earth elements at the A site and Mn elements at the B site, and defect dipoles are formed, the dipoles are stretched after a positive electric field is applied, and large unipolar strain is induced near the phase transition point.

[0021] 2. The preparation method has simple flow and is easy to realize, and is beneficial to realize industrialized scale production.

[0022] The prepared sodium bismuth titanate ceramic has S-y of 80 o C and electric field 5.5 kV / mm, the maximum strain value of the electro-strain is 1.92%, the prepared sodium bismuth titanate ceramic has L-y of 80 o C and electric field 6.5 kV / mm, the maximum strain value of the electro-strain is 2.63%, and the relaxor phase and the ferroelectric phase realize reversible conversion under the excitation of an external field. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 X-ray diffraction patterns of the prepared sodium bismuth titanate ceramic materials S-10 and S-20 system samples of the embodiments 1 and 2 of the application; Figure 2 The prepared sodium bismuth titanate ceramic materials S-10 and S-20 system samples of the embodiments 1 and 2 of the application respectively have the electric hysteresis loops (P-E) of 80 d C (S-10-80 o C) and 80 o C (S-20-80 o C) near the phase transition point T o Figure 3 The prepared sodium bismuth titanate ceramic materials S-10 and S-20 system samples of the embodiments 1 and 2 of the application respectively have the electric hysteresis loops (P-E) of 80 d C (S-10-80 o C) and 80 o C (S-20-80 o ​C (S-20-80 o C) of the electric field-strain curve (S-E) of the L-05, L-10, L-15, and L-20 system samples prepared in Example 3, 4, 5, and 6 of the present application, respectively, at the phase transition point T Figure 4 Temperature dependence curves of the dielectric constant of the L-05, L-10, L-15, and L-20 system samples prepared in Example 3, 4, 5, and 6 of the present application, respectively. Figure 5 X-ray diffraction patterns of the L-05, L-10, L-15, and L-20 system samples prepared in Example 3, 4, 5, and 6 of the present application, respectively. Figure 6 The electric hysteresis loops (P-E) of the L-05, L-10, L-15, and L-20 system samples prepared in Example 3, 4, 5, and 6 of the present application, respectively, at the phase transition point T d Nearby 70 o C (L-05-70 o C), 80 o C (L-10-80 o C), 80 o C (L-15-80 o C), and 70 o C (L-20-80 o C) of the electric field-strain curve (S-E) of the L-05, L-10, L-15, and L-20 system samples prepared in Example 3, 4, 5, and 6 of the present application, respectively, at the phase transition point T Figure 7 The electric hysteresis loops (P-E) of the L-05, L-10, L-15, and L-20 system samples prepared in Example 3, 4, 5, and 6 of the present application, respectively, at the phase transition point T d Nearby 70 o C (L-05-70 o C), 80 o C (L-10-80 o C), 80 o C (L-15-80 o C), and 70 o C (L-20-80 o C) of the electric field-strain curve (S-E) of the L-05, L-10, L-15, and L-20 system samples prepared in Example 3, 4, 5, and 6 of the present application, respectively, at the phase transition point T Figure 8 Temperature dependence curves of the dielectric constant of the L-05, L-10, L-15, and L-20 system samples prepared in Example 3, 4, 5, and 6 of the present application, respectively. DETAILED DESCRIPTION

[0024] The present application is further described in detail by the following examples. It is to be specifically understood, however, that the following examples are merely illustrative and are not intended to be limiting on the scope of the present application. Raw materials used in the following examples are commercially available unless otherwise specified.

[0025] Embodiment 1 The chemical general formula of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material of this embodiment is [a(Bi 0.5 Na 0.5 TiO3)-b(BaTiO3)]-xMn-yR(R is a Sm element), wherein a = 0.95, b = 0.05, x = 0.5%, y = 1.0% is abbreviated as (S-10).

[0026] The preparation method of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material described above comprises the following steps: (1) batching and synthesis According to the mole percentage, analytical pure bismuth oxide Bi2O3, sodium carbonate Na2CO3, titanium dioxide TiO2, barium carbonate BaCO3, manganese dioxide MnO2, and samarium sesquioxide Sm2O3 are weighed as raw materials. Put into the ball mill tank, 500 r / min ball milling for 10 hours, 70 o C drying, grinding and sieving to obtain mixed powder.

[0027] (2) pre-sintering Put the mixed powder in step (1) into a muffle furnace, pre-sinter at 820 o C, keep warm for 4 h, and naturally cool to room temperature to obtain pre-sintered powder.

[0028] (3) secondary ball milling Grind and sieve the pre-sintered powder in step (2), 500 r / min ball milling for 10 h, 70 o C drying to obtain ball milled powder.

[0029] (4) granulation Grind and sieve the ball milled powder dried in step (3), and fully mix and stir with 5% polyvinyl alcohol (PVA) solution or distilled water by weight to granulate, 100 mesh sieving to obtain granulated powder.

[0030] (5) forming Use a die with a diameter of 10 mm to press the granulated powder after granulation in step (4) into a circular sheet shape under a pressure of 110 Mpa using an electric tablet press, and the diameter of the dry powder circular sheet is 10 mm and the thickness is about 1 mm.

[0031] (6) sintering Put the blank in step (5) into a muffle furnace, sinter at a rate of 3 o C / min to 1105 °C, keep warm for 4 h, and naturally cool to room temperature with the furnace to obtain a sintered sample.

[0032] (7) burning electrode The sintered sample in step (6) above was polished to 400 μm, the upper and lower surfaces were coated with silver paste, and the sample was placed in a muffle furnace and heat treated at 600 o C for 0.5 h to obtain a sodium bismuth titanate-based ceramic material S-10.

[0033] Example 2 The chemical general formula of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material in this example is [a(Bi 0.5 Na 0.5 TiO3)-b(BaTiO3)]-xMn-yR (R is a Sm element), where a = 0.95, b = 0.05, x = 0.5%, and y = 2.0%, which is abbreviated as (S-20).

[0034] The preparation method of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material above in Example 1 is different in that the Sm content in this example is 2.0%.

[0035] Example 3 The chemical general formula of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material in this example is [a(Bi 0.5 Na 0.5 TiO3)-b(BaTiO3)]-xMn-yR (R is a La element), where a = 0.95, b = 0.05, x = 0.5%, and y = 0.5%, which is abbreviated as (L-05).

[0036] The preparation method of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material above in Example 1 is different in that the Sm content in this example is 2.0%.

[0037] Example 4 The chemical general formula of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material in this example is [a(Bi 0.5 Na 0.5 TiO3)-b(BaTiO3)]-xMn-yR (R is a La element), where a = 0.95, b = 0.05, x = 0.5%, and y = 1.0%, which is abbreviated as (L-10).

[0038] The preparation method of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material above in Example 1 is different in that the Sm content in this example is 2.0%.

[0039] Example 5 The chemical general formula of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material in this example is [a(Bi 0.5 Na0.5 TiO3)-b(BaTiO3)]-xMn-yR(R is La element), wherein a = 0.95, b = 0.05, x = 0.5%, y = 1.5% is abbreviated as (L-15).

[0040] The preparation method of the above-mentioned large unipolar electrostrictive sodium bismuth titanate-based ceramic is the same as that of Example 5, except that the content of the rare earth element La in this example is 1.5%.

[0041] Example 6 The chemical general formula of the large unipolar electrostrictive sodium bismuth titanate-based ceramic material in this example is [a(Bi 0.5 Na 0.5 TiO3)-b(BaTiO3)]-xMn-yR(R is La element), wherein a = 0.95, b = 0.05, x = 0.5%, y = 2.0% is abbreviated as (L-20).

[0042] The preparation method of the above-mentioned large unipolar electrostrictive sodium bismuth titanate-based ceramic is the same as that of Example 5, except that the content of the rare earth element La in this example is 2.0%.

[0043] As shown in Figure 1, the large unipolar electrostrictive sodium bismuth titanate-based ceramic described in Examples 1-2, both groups of samples are single perovskite structure, and the diffraction peaks are single peaks without appearing impurity phases, which shows that Sm and Mn elements can be fully solid-solved into BNBT crystals to replace A-site / B-site ions without causing large changes in crystal structure.

[0044] As seen from Figures 2 and 3, the polarization value of the positive electric field of Examples 1 and 2 after sintering in air is higher than that of the negative electric field, which indicates that after Sm element doping at A-site and Mn element doping at B-site, A-site vacancies and oxygen vacancies are introduced and defect dipoles are formed. After applying a positive electric field, the dipoles are stretched, causing large unipolar strain, and after applying a reverse electric field, the defect dipoles are compressed, reducing their negative strain value. Moreover, it can be seen that the maximum strain value of the sample treated in air atmosphere increases with the increase of Sm content as shown in Figure 4. Figure 3 o C- The strain value of the sample is 1.53%, and the maximum strain value of the S-20 ceramic sample under the action of an electric field of 5.5 kV / mm is 1.92%, which is an increase of 0.39% compared with the C- sample. This enhancement is closely related to the enhancement of ferroelectricity caused by Sm rare earth doping and strain polarity coupling. o C- The strain value of the sample is 1.53%, and the maximum strain value of the S-20 ceramic sample under the action of an electric field of 5.5 kV / mm is 1.92%, which is an increase of 0.39% compared with the C- sample. This enhancement is closely related to the enhancement of ferroelectricity caused by Sm rare earth doping and strain polarity coupling.

[0045] As can be seen from Figure 5, the temperature dependence of the dielectric constant of the ceramic material samples of Examples 1 and 2 is shown, and the dielectric constant of the ceramic material samples of Examples 1 and 2 is shown in Figure 6. Figure 4 As can be seen from Figure 5, the temperature dependence of the dielectric constant of the ceramic material samples of Examples 1 and 2 is shown, and the dielectric constant of the ceramic material samples of Examples 1 and 2 is shown in Figure 6. o ​Measurements were taken at a frequency of 500 Hz within the temperature range of C. Prior to dielectric testing, all ceramic samples were polarized under an electric field, clearly depicting the relaxation ferroelectric transition temperature T. d It was observed that from Example 1 to Example 2, T d Value from 77 o C decreased slightly to 74 o C.

[0046] like Figure 5 As shown, the X-ray diffraction patterns of the sodium bismuth titanate-based ceramics in Example 4 all exhibit a single perovskite structure with sharp characteristic diffraction peaks and no impurities or secondary phases. This indicates that La and Mn elements can be fully dissolved and replace A / B site ions without significantly altering the crystal structure. Only minor adjustments to the lattice parameters occur, ensuring structural integrity.

[0047] As shown in Figure 6, the hysteresis loops of all four groups of BNT rare-earth-doped ceramics exhibit excellent ferroelectric response, high polarization intensity, and good loop closure. The sufficient solid solution of rare-earth elements in this system effectively optimizes the dynamic behavior of the ferroelectric domains, providing a key structural guarantee for achieving large electrostrain performance. Meanwhile, the polarization curves of the positive and negative electric field regions in the embodiments show a certain degree of asymmetry, reflecting the asymmetric characteristics of the internal domain structure. This phenomenon indicates that after doping with La at the A-site and Mn at the B-site, A-site vacancies and oxygen vacancies are introduced into the material, promoting the formation of defect dipoles between the dopant ions and oxygen vacancies. These defect dipoles align oriented along the polarization direction during the polarization treatment, thereby endowing the material with a significant unilateral large strain effect.

[0048] As shown in Figure 7, among the samples treated in air, the maximum strain value first increases and then decreases with increasing La content. The sample treated at L⁻¹⁰–80 °C with an electric field of 6.5 kV / mm exhibits the highest electrostricted strain value at 2.63%. This enhancement effect is closely related to the improved ferroelectric properties and strain-polarization coupling caused by La rare-earth doping. Trace La doping induces a suitable amount of A-site vacancies, which pair with oxygen vacancies to form favorable defect dipoles, thereby generating a moderate bias field within the material. This bias field promotes the ordered orientation and reversible flipping of domains in specific directions, thus exhibiting a larger electrostricted strain on a macroscopic scale.

[0049] Figure 8 shows the relationship between the dielectric constant and temperature of the ceramic samples prepared in Examples 3-6 within a temperature range of -50 to 270 °C and a frequency of 1000 Hz. Before dielectric testing, all samples were polarized by an external electric field, thus enabling clear identification of the relaxation ferroelectric transition temperature (T0). d The results showed that T in Examples 3-6d The value shows a trend of first increasing and then decreasing, and the change range is mainly concentrated around about 70 °C.

[0050] Therefore, the application adopts the above-mentioned large unipolar electrostrictive sodium bismuth titanate-based ceramic and its preparation method, and the prepared sodium bismuth titanate-based ceramic has a large electrostrictive strain.

[0051] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A sodium bismuth titanate-based ceramic material having a large unipolar electrostrain, characterized in that, Raw material components and their molar percentage contents are [a(Bi 0.5 Na 0.5 TiO3)-b(BaTiO3)]-xMn-yR, R is a rare earth element, wherein a = 0.90-0.98, b = 0.02-0.1, a+b = 1, x is the doping amount of Mn, which is 0.1%-3% in terms of molar percentage, and y is the doping amount of R, which is 0.1%-3% in terms of molar percentage.

2. The sodium bismuth titanate-based ceramic according to claim 1, characterized in that, a = 0.95, b = 0.05, x = 0.5%, y = 1.0-2.0%, R is selected from La, Sm, when R is selected from La, the sodium bismuth titanate-based ceramic material is abbreviated as L-y, and when R is selected from Sm, the sodium bismuth titanate-based ceramic material is abbreviated as S-y.

3. The method of producing a sodium bismuth titanate-based ceramic material having a large unipolar electrostriction according to claim 1, characterized by, Prepared by a solid-phase synthesis method, comprising the following steps: (1) ingredient synthesis The raw materials Bi2O3, Na2CO3, TiO2, BaCO3, MnO2 and the oxide of R are weighed according to the molar ratio of the raw material components in claim 1 or 2, and are loaded into a ball mill tank, ball milled, dried, ground and sieved to obtain a mixed powder; wherein the raw material is La2O3 when R is La, and the raw material is Sm2O3 when R is Sm; (2) pre-sintering The mixed powder in step (1) is placed in a muffle furnace, 700-950 o C, pre-sintered for 3-8 h, and naturally cooled to room temperature to obtain a pre-sintered powder; (3) secondary ball milling The pre-sintered powder in step (2) is ground, sieved, ball milled and dried to obtain a ball milled powder; (4) granulation The ball milled powder dried in step (3) is ground, sieved, and then fully mixed and stirred with polyvinyl alcohol (PVA) or distilled water, sieved to obtain a granulated powder; (5) forming The granulated powder in step (4) is pressed and formed into a cylindrical blank under a pressure of not less than 100 MPa; (6) sintering The blank in step (5) is placed in a muffle furnace, heated at 3 °C / min to 1050 °C-1250 °C for sintering, and held for 2-6 h, and then naturally cooled to room temperature with the furnace to obtain a sintered sample; (7) burning electrode The sintered sample in step (6) above is polished, the upper and lower surfaces are smeared with silver paste and placed in a muffle furnace at 500-600 o C heat treatment for 0.5-1 h to obtain the sodium bismuth titanate-based ceramic material.

4. The method of producing a sodium bismuth titanate-based ceramic material according to claim 3, characterized by, In the step (1) and step (3), the ball mill tank is a nylon tank, the ball mill medium is anhydrous ethanol and zirconium ball, the ball mill rotation speed is 300-500 r / min, the ball mill time is 6-14 h, the drying temperature is 70-100 o C.

5. The method of producing a sodium bismuth titanate-based ceramic material according to claim 3, characterized by, In step (2), the mixed powder is placed in a crucible, compacted and placed in a Bi2O3 atmosphere for pre-sintering in a muffle furnace.

6. The method of producing a sodium bismuth titanate-based ceramic material according to claim 3, characterized by, In step (4), polyvinyl alcohol (PVA) or distilled water is uniformly mixed with the ball milled powder, and the mass percentage of polyvinyl alcohol (PVA) or distilled water in the whole is 3-8%, and both times of sieving use a 100 mesh sieve.

7. The method of producing a sodium bismuth titanate-based ceramic material according to claim 3, characterized by, In step (5), the pressing and forming is followed by pressure holding treatment.

8. The method of producing a sodium bismuth titanate-based ceramic material according to claim 3, characterized by, In step (7), the sintered sample is polished to a thickness of 300-500 μm.

9. The sodium bismuth titanate-based ceramic prepared according to the production process according to any one of claims 3 to 8, characterized in that When the doped rare earth element is Sm, S-y is 80 o The maximum strain value of the electro-strain under the action of C and electric field 5.5 kV / mm is 1.92%.

10. The sodium bismuth titanate-based ceramic prepared according to the production process according to any one of claims 3 to 8, characterized in that L-y is 80 when the doped rare earth element is La o The maximum strain value of the electro-strain under the action of C and electric field 6.5 kV / mm is 2.63%.

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