Na and Nd co-doped CaBi4Ti4O15 piezoelectric ceramic material and preparation method thereof

Abstract

The invention relates to a Na and Nd co-doped CaBi4Ti4O15 piezoelectric ceramic material and a preparation method thereof, A-site Ca < 2 + > material in CBT ceramic is replaced with Na < + > and Nd < 3 + > ions, A-site double-ion doping is realized, and single-phase solid solution ceramic is obtained; ions with different radiuses enter the same site, so that the ceramic oxygen octahedron is inclined along the spontaneous polarization direction, the spontaneous polarization intensity is improved, and the piezoelectric constant of a high material is increased to the highest 24pC / N from 6pC / N of pure CBT. According to the invention, the doping amount of Na and Nd in the ceramic is increased, part of pores in the ceramic are gradually reduced along with the increase of the doping amount of Na and Nd, the density of the ceramic is improved, and the larger grain size can reduce the number of grain boundaries and the stress between grains, so that the movement of domain walls under an electric field is promoted, and the positive influence on the piezoelectric property is generated. The Na and Nd co-doped CaBi4Ti4O15 piezoelectric ceramic material obtained by the preparation method disclosed by the invention has high piezoelectric constant and high-temperature resistivity on the premise of ensuring relatively high Curie temperature, and an effective way is provided for synthesizing the piezoelectric ceramic material with high piezoelectric constant and high-temperature resistivity.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic functional materials, and particularly to a Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material and a preparation method thereof. Background Art

[0002] In recent years, with the development of technology and the further expansion of the application scope of piezoelectric ceramics, new requirements have been put forward for the performance of piezoelectric ceramics in high-temperature extreme service environments, such as ultrasonic high-temperature welding, fuel injection piezoelectric valves in internal combustion engines, high-temperature ultrasonic positioning detectors used in nuclear reactors, and high-temperature piezoelectric acceleration sensors widely used in aircraft engines. In order to ensure that piezoelectric devices can work normally in these high-temperature environments, it is necessary to select piezoelectric materials with a high Curie temperature, high resistivity at high temperatures, and good temperature stability. At present, the Curie temperatures of traditional piezoelectric ceramic materials represented by PZT are mostly below 400 °C. Therefore, the development of high-Curie temperature piezoelectric ceramics with good piezoelectric properties is one of the research hotspots in the field of piezoelectric materials.

[0003] Calcium bismuth titanate (CaBi4Ti4O 15 , abbreviated as CBT) is a kind of bismuth layer-structured compound and is a bismuth layer-structured ferroelectric with m = 4. The Curie temperature (T 15 ) of CaBi4Ti4O c is about 790 °C, which is a high-Curie temperature Aurivillius phase ferroelectric. And due to its good thermal stability, anti-fatigue property, and low dielectric loss, it is one of the potential candidate materials for high-temperature piezoelectric and ferroelectric applications such as sensors, filters, or oscillators.

[0004] In the invention disclosed in the publication number CN105837200A, a manganese-doped calcium lithium cerium niobium bismuth titanate ceramic material and a preparation method thereof are disclosed. This method is a CBT-based piezoelectric ceramic material with A-site Li and Ce co-doped and B-site doped with Nb, and MnCO3 is added to the matrix to significantly increase the d 33 of the ceramic to 18.5 pC / N. Its chemical composition general formula is Ca 1-x (Li,Ce) x / 2Bi4Ti 4-y Nb y O 15 -zMnCO3, but its high-temperature resistivity is not studied.

[0005] In the invention disclosed in the publication number CN110698195A, a high-resistivity, high-voltage electroactive calcium bismuth titanate-based high-temperature piezoelectric ceramic and its preparation method are disclosed. This invention is a CBT-based piezoelectric ceramic material co-doped with Mn and Ta at the B-site. The prepared ceramic, while ensuring a relatively high Curie temperature, has its d 33 increased to 16 pC / N, and its chemical composition general formula is CaBi4Ti 4-x (Mn 1 / 3 Ta 2 / 3 ) x O 15 . However, the high-temperature resistivity of the ceramic at 600 °C has not been studied.

[0006] In the invention disclosed in the publication number CN113896526A, a piezoelectric material with high piezoelectricity and good high-temperature insulation and its preparation method are disclosed. It is a CBT-based piezoelectric ceramic material and its preparation method co-doped with Na and Bi at the A-site and Nb and Cu at the B-site, effectively increasing the d 33 of the ceramic to 16 pC / N, and at the same time having good thermal stability. Its chemical composition general formula is Ca 1-x (Na 0.5 Bi 0.5 ) x Bi4Ti 4-y (Nb 2 / 3 Cu 1 / 3 ) y O 15 .

[0007] In the invention disclosed in the publication number CN114455944A, a bismuth layer-structured piezoelectric ceramic material and its preparation method are disclosed. It is a CBT-based piezoelectric ceramic material and its preparation method co-doped with Li at the A-site and Ni and W at the B-site. Its chemical composition general formula is Ca (1-x) Li 2x Bi4Ti 4-y (Ni 2 / 3 W 1 / 3 ) y O 15 +zwt% ZnO.

[0008] In the invention disclosed in the publication number CN116751052A, a bismuth layer-structured piezoelectric ceramic material and its preparation method and application are disclosed. It is a CBT-based piezoelectric ceramic material and its preparation method co-doped with Nb and Mn at the B-site, significantly improving the high-temperature resistivity of the CBT ceramic. Its chemical composition general formula is CaBi4Ti 4-x (Nb 2 / 3 Mn 1 / 3 ) x O 15 .

[0009] In DOI: 10.1016 / j.actamat.2022.118146, Jingwen Xi et al. publicly published the paper "Origin of high piezoelectricity in CBT-based Aurivillius ferroelectrics: Glide of (Bi2O2) 2+ blocks and suppressed internal bias field". This paper obtained Ce-doped CBT-based piezoelectric ceramics with both high d 33 (~21 pC / N) and high resistivity (~1.17×10 7 Ω·cm), and studied the origin of their high piezoelectricity.

[0010] In DOI: 10.1016 / j.jeurceramsoc.2022.06.049, Guohao Li et al. publicly published the paper "Textured CaBi4Ti4O 15 ceramics with large piezoelectricity, excellent thermal stability and high resistivity". This paper prepared highly textured CaBi4Ti4O 15 piezoelectric ceramics with an orientation factor of 82% by spark plasma sintering technology. Parallel to the pressure direction, T c of 788 °C and a good match of d 33 of 24.2 pC / N were obtained, and the high-temperature electrical transport properties of the ceramics at 500 °C were also studied.

[0011] In DOI: 10.26599 / JAC.2023.9220754, Zimeng Hu et al. publicly published the paper "Enhanced piezoelectricity in Na and Ce co-doped CaBi4Ti4O 15 ceramics for high-temperature applications". On the premise of ensuring a relatively high Curie temperature, this paper increased the d 33 of CBT-based piezoelectric ceramics to 19.5 pC / N and explained the reason for the improvement of piezoelectric properties, but did not study the high-temperature resistivity.

[0012] However, the piezoelectric constant (d 33) is still relatively low, generally below 20 pC / N. At the same time, the resistivity of CBT ceramics decreases significantly at high temperatures. At 600 °C, the resistivity is only 7×10 5 Ω·cm. Therefore, on the premise of maintaining a high Curie temperature, improving the piezoelectric constant and high-temperature resistivity of CBT-based high-Curie temperature piezoelectric ceramic materials has become an important topic in the research field of high-temperature piezoelectric materials.

[0013] At present, there is no report on the preparation of Na, Nd co-doped CBT-based high-temperature piezoelectric ceramic materials Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 , (x = 0.03 - 0.12) and their microstructures, dielectric properties, piezoelectric properties and high-temperature resistivity. Summary of the Invention

[0014] To overcome the problems in the prior art that the piezoelectric constant and high-temperature resistivity of CBT-based piezoelectric ceramics are low and cannot be practically applied at high temperatures, the present invention proposes a Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material and its preparation method.

[0015] The Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material proposed by the present invention is characterized in that the chemical composition of the CaBi4Ti4O 15 piezoelectric ceramic material is Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 , where x = 0.03 to 0.12.

[0016] The raw materials for generating the Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 are CaCO3, Bi2O3, TiO2, NaCO3 and Nd2O3, and each of the raw materials is of analytical purity and the particle size is in the micron range.

[0017] The preparation process of the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material is as follows:

[0018] Step 1, batching:

[0019] According to Ca 1-x(Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 Weigh the initial raw materials CaCO3, SrCO3, BaCO3, PbO, Bi2O3 and TiO2 in stoichiometric ratios of the chemical formula;

[0020] Step 2, prepare the mixed powder:

[0021] Add anhydrous ethanol to the weighed initial raw materials, mix them and ball mill for 8 - 12 h to obtain a mixture. Dry the obtained mixture to obtain the mixed powder.

[0022] When preparing the mixed powder, the mass ratio of the anhydrous ethanol to the initial raw materials is 1:1. The drying temperature is 50 - 80 °C and the drying time is 12 h.

[0023] Step 3, prepare the pre-synthesized powder:

[0024] Place the obtained mixed powder in a pre-sintering furnace; pre-sinter the mixed powder to obtain the pre-synthesized powder.

[0025] When preparing the pre-synthesized powder, the pre-sintering temperature is 800 - 950 °C and the heat preservation time is 4 h; after the heat preservation ends, cool it to 500 °C at a rate of 5 - 10 °C / min and then cool it to room temperature with the furnace.

[0026] The heating rate of the pre-sintering furnace is 5 - 10 °C / min.

[0027] Step 4, ball mill:

[0028] Add anhydrous ethanol to the obtained pre-synthesized powder; ball mill for 8 - 12 h and then dry it to obtain the pre-synthesized powder.

[0029] The mass ratio of the anhydrous ethanol to the powder is 1:1.

[0030] Step 5, granulate and press:

[0031] Add PVA aqueous solution to the pre-synthesized powder after the second ball milling, and the mass ratio of the PVA aqueous solution to the pre-synthesized powder is 1:5; mix evenly and then screen to obtain fine particles. Place the obtained fine particles in a tablet press to press into a ceramic green body.

[0032] When granulating and pressing, the concentration of the PVA aqueous solution is 5 wt.%; the particle size of the fine particles is 50 - 100 mesh; the pressure of the pressing is 2 - 5 MPa.

[0033] Step 6, prepare the ceramic green body:

[0034] Place the ceramic green body in an alumina crucible; place the alumina crucible containing the ceramic green body in a box furnace to degrease the ceramic green body. After the heat preservation is completed, cool it to room temperature with the furnace to obtain a degreased ceramic green body.

[0035] When preparing the ceramic green body, the temperature of the box furnace is 600 - 700 °C, and the heat preservation time is 3 h; the heating rate of the box furnace is 2 - 5 °C / min.

[0036] Step 7, sintering:

[0037] Place the obtained ceramic green body in an alumina crucible and put it into a box furnace. Sinter the ceramic green body.

[0038] Take out the sintered ceramic green body, polish it to obtain a Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material.

[0039] During sintering, the temperature of the box furnace is 1050 - 1200 °C, and the heat preservation time is 2 - 4 h; the heating rate of the box furnace is 2 - 5 °C / min; after the heat preservation is completed, the box furnace cools down to 500 °C at a rate of 5 - 10 °C / min; then cool it to room temperature with the furnace. Obtain a Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material.

[0040] The purpose of the present invention is to provide a Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material and its preparation method, which has simple operation and low requirements for equipment. The obtained Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material has high piezoelectric constant and high-temperature resistivity on the premise of ensuring a relatively high Curie temperature. The present invention provides an effective way for synthesizing piezoelectric ceramic materials with high piezoelectric constant and high-temperature resistivity.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] The Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material obtained by the present invention has the chemical formula Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 , (x = 0.03 - 0.12).

[0043] The present invention uses two ions of Na + , Nd 3+ to replace Ca at the A-site in the CBT ceramic 2+The material composition design concept has successfully achieved double-ion doping at the A-site and obtained a single-phase solid solution ceramic. The piezoelectric constant of the doped ceramic has increased by nearly 4 times compared with pure CBT. Attached Figure 5 shows the piezoelectric constant of the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material obtained by the process of the present invention. The results show that the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material of the present invention can effectively improve the piezoelectric coefficient of the material. Specifically, the piezoelectric constant increases from 6 pC / N of pure CBT to the highest 24 pC / N. This is mainly because ions with different radii enter the same site, causing the ceramic oxygen octahedron to tilt along the direction of spontaneous polarization, increasing the spontaneous polarization intensity. At the same time, attached Figure 2 shows the Na, Nd co-doped CaBi4Ti4O 15 scanning electron microscope photos of the microstructure of the piezoelectric ceramic material obtained by the process of the present invention. It can be seen from the figure that the grain flake morphology inside the ceramic is obvious, the structure is dense, there are few pores in the sample microstructure, and as the doping amount of Na and Nd increases, the pores inside the ceramic sample gradually decrease, indicating that appropriate additives can improve the density of the ceramic. Moreover, as the doping amount increases, the grain size inside the ceramic increases. Larger grain sizes can reduce the number of grain boundaries and the stress between grains, thereby promoting the movement of domain walls under the electric field and having a positive impact on the piezoelectric properties.

[0044] Attached Figure 4 is the resistivity-temperature change curve of the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material obtained by the process of the present invention. The results show that the ceramic material obtained by the process of the present invention can effectively improve the resistivity of the material. Specifically, the high-temperature resistivity at 600 °C can increase from 7×10 5 Ω·cm of pure CBT to 5.6×10 6 Ω·cm, an increase of nearly an order of magnitude. This is mainly because there is stress near the grain boundaries, and the defect density in the grains increases as they approach these boundaries. The larger grains in the doped samples are related to the reduced average density of charge defects, thus increasing the resistivity of the CBT-based ceramics.

[0045] The Curie temperature is also an important physical parameter of piezoelectric materials. Attached Figure 3 is the dielectric constant and dielectric loss-temperature change curve of the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material obtained by the process of the present invention. It can be seen that the ceramic material obtained by the design concept of double doping of Na and Nd in the present invention has improved the piezoelectric properties and high-temperature resistivity of the ceramic while maintaining a high Curie temperature. The Curie temperature is specifically 751 °C - 769 °C, and as the doping amount increases, the dielectric loss of the ceramic decreases.

[0046] In summary, compared with the unmodified CaBi4Ti4O 15 piezoelectric ceramic material, the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material obtained in the present invention has a significant increase in piezoelectric constant and high-temperature resistivity while ensuring a high Curie temperature, making it have practical application value in the field of high-temperature piezoelectric sensors. Description of the Drawings

[0047] Figure 1 X-ray diffraction pattern of the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material prepared from CaCO3, Bi2O3, TiO2, NaCO3 and Nd2O3 in the present invention.

[0048] Figure 2 SEM and particle size statistical chart of the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material prepared from CaCO3, Bi2O3, TiO2, NaCO3 and Nd2O3 in the present invention. Figure 2 a is the SEM morphology of the surface of Ca 0.97 (Na 0.5 Nd 0.5 ) 0.03 Bi4Ti4O 15 ceramic, Figure 2 b is the SEM morphology of the surface of Ca 0.94 (Na 0.5 Nd 0.5 ) 0.06 Bi4Ti4O 15 ceramic, Figure 2 c is the SEM morphology of the surface of Ca 0.91 (Na 0.5 Nd 0.5 ) 0.09 Bi4Ti4O 15 ceramic, Figure 2 d is the SEM morphology of the surface of Ca 0.88 (Na 0.5 Nd 0.5 ) 0.12 Bi4Ti4O 15 ceramic, Figure 2 e is the particle size distribution statistical chart corresponding to different x values (x = 0.03 - 0.12) of Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 ceramic.

[0049] Figure 3Na, Nd co-doped CaBi4Ti4O made from CaCO3, Bi2O3, TiO2, NaCO3 and Nd2O3 according to the present invention 15 Dielectric temperature spectrum of the piezoelectric ceramic material Figure 3 a is the curve of the ceramic dielectric constant varying with temperature Figure 3 b is the curve of the ceramic dielectric loss varying with temperature

[0050] Figure 4 Na, Nd co-doped CaBi4Ti4O made from CaCO3, Bi2O3, TiO2, NaCO3 and Nd2O3 according to the present invention 15 Curve of the resistivity of the piezoelectric ceramic material varying with temperature

[0051] Figure 5 Na, Nd co-doped CaBi4Ti4O made from CaCO3, Bi2O3, TiO2, NaCO3 and Nd2O3 according to the present invention 15 Piezoelectric constants corresponding to different x values of the piezoelectric ceramic material

[0052] Figure 6 Flow chart of the present invention

[0053] In the figure: 1 is Ca 0.97 (Na 0.5 Nd 0.5 ) 0.03 Bi4Ti4O 15 X-ray diffraction pattern

[0054] 2 is Ca 0.94 (Na 0.5 Nd 0.5 ) 0.06 Bi4Ti4O 15 X-ray diffraction pattern

[0055] 3 is Ca 0.91 (Na 0.5 Nd 0.5 ) 0.09 Bi4Ti4O 15 X-ray diffraction pattern

[0056] 4 is Ca 0.88 (Na 0.5 Nd 0.5 ) 0.12 Bi4Ti4O 15 X-ray diffraction pattern

[0057] 5 is Ca 0.97 (Na 0.5 Nd 0.5 ) 0.03Bi4Ti4O 15 Curves of dielectric constant of Bi4Ti4O varying with temperature;

[0058] 6 is Ca 0.94 (Na 0.5 Nd 0.5 ) 0.06 Bi4Ti4O 15 Curves of dielectric constant of Bi4Ti4O varying with temperature;

[0059] 7 is Ca 0.91 (Na 0.5 Nd 0.5 ) 0.09 Bi4Ti4O 15 Curves of dielectric constant of Bi4Ti4O varying with temperature;

[0060] 8 is Ca 0.88 (Na 0.5 Nd 0.5 ) 0.12 Bi4Ti4O 15 Curves of dielectric constant of Bi4Ti4O varying with temperature;

[0061] 9 is Ca 0.97 (Na 0.5 Nd 0.5 ) 0.03 Bi4Ti4O 15 Curves of dielectric loss of Bi4Ti4O varying with temperature;

[0062] 10 is Ca 0.94 (Na 0.5 Nd 0.5 ) 0.06 Bi4Ti4O 15 Curves of dielectric loss of Bi4Ti4O varying with temperature;

[0063] 11 is Ca 0.91 (Na 0.5 Nd 0.5 ) 0.09 Bi4Ti4O 15 Curves of dielectric loss of Bi4Ti4O varying with temperature;

[0064] 12 is Ca 0.88 (Na 0.5 Nd 0.5 ) 0.12 Bi4Ti4O 15 Curves of dielectric loss of Bi4Ti4O varying with temperature;

[0065] 13 is Ca 0.97 (Na 0.5 Nd 0.5 ) 0.03 Bi4Ti4O 15The resistivity variation curve with temperature;

[0066] 14 is Ca 0.94 (Na 0.5 Nd 0.5 ) 0.06 Bi4Ti4O 15 The resistivity variation curve with temperature;

[0067] 15 is Ca 0.91 (Na 0.5 Nd 0.5 ) 0.09 Bi4Ti4O 15 The resistivity variation curve with temperature;

[0068] 16 is Ca 0.88 (Na 0.5 Nd 0.5 ) 0.12 Bi4Ti4O 15 The resistivity variation curve with temperature;

[0069] 17 is the average thickness of the thickness of the flaky grains;

[0070] 18 is the average particle size of the flaky grains. Specific embodiments

[0071] The present invention is a Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material and its preparation method, and its technical solution will be described in detail through six embodiments.

[0072] The reagents used in the embodiments of the present invention are all commercially available analytical pure products, and the manufacturers are all Sinopharm Chemical Reagent Co., Ltd., and the purity is > 99.9%.

[0073] The Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material proposed by the present invention has a chemical composition of Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 , where x = 0.03 - 0.12.

[0074] Table 1 Components and dosages of each embodiment

[0075]

[0076] The specific process for preparing the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material proposed by the present invention is as follows:

[0077] Step 1, batching:

[0078] Accurately weigh the initial raw materials CaCO3, SrCO3, BaCO3, PbO, Bi2O3 and TiO2 according to the stoichiometric ratio of the chemical formula Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 ; The dosages of the CaCO3, Bi2O3, TiO2, NaCO3 and Nd2O3 are obtained according to the value of x. In each embodiment of the present invention, the chemical formulas are respectively Ca

[0079] (Na 0.97 (Na 0.5 Nd 0.5 ) 0.03 Bi4Ti4O 15 Ca 0.94 (Na 0.5 Nd 0.5 ) 0.06 Bi4Ti4O 15 Ca 0.91 (Na 0.5 Nd 0.5 ) 0.09 Bi4Ti4O 15 Ca 0.88 (Na 0.5 Nd 0.5 ) 0.12 Bi4Ti4O 15 Ca 0.92 (Na 0.5 Nd 0.5 ) 0.08 Bi4Ti4O 15 Ca 0.9 (Na 0.5 Nd 0.5 ) 0.1 Bi4Ti4O 15 , and are obtained from the contents of each element in the chemical formula.

[0080] Step 2, preparing the mixed powder:

[0081] Add anhydrous ethanol to the initial raw materials weighed in Step 1, mix them and ball-mill for 8 - 12 h to obtain a mixture. The mass ratio of the anhydrous ethanol to the initial raw materials is 1:1. Put the obtained mixture into an oven and dry it at 50 - 80 °C for 12 h to obtain the mixed powder.

[0082] Table 2 Process parameters of each embodiment in Step 1

[0083]

[0084] Step 3, prepare the pre-synthesized powder:

[0085] Place the mixed powder obtained in Step 2 into a pre-sintering furnace. Heat the pre-sintering furnace to 800 - 950°C at a heating rate of 5 - 10°C / min and hold for 4 h to pre-sinter the mixed powder. After the holding is completed, cool it to 500°C at a rate of 5 - 10°C / min and then cool it to room temperature with the furnace to obtain the pre-synthesized powder.

[0086] Table 3 Process parameters of each example in Step 2

[0087]

[0088] Step 4, ball milling:

[0089] Add anhydrous ethanol to the pre-synthesized powder obtained in Step 3 and ball mill for 8 - 12 h. The mass ratio of the anhydrous ethanol to the powder is 1:1 to obtain a mixed material. Place the mixed material in an oven and dry it at 60 - 80°C for 12 h to obtain the pre-synthesized powder.

[0090] Table 4 Process parameters of each example in Step 4

[0091]

[0092] Step 5, granulation and tabletting:

[0093] Add a 5 wt.% aqueous PVA solution to the pre-synthesized powder after the secondary ball milling; the addition amount of the PVA aqueous solution and the mass of the pre-synthesized powder after the secondary ball milling is 1:5. Mix evenly, sieve, and take the particles with a mesh size of 50 - 100. Place the sieved particles in a tabletting machine and tablet at 2 - 5 MPa to obtain a ceramic green body.

[0094] Table 5 Process parameters of each example in Step 5

[0095]

[0096] Step 6, prepare the ceramic green body:

[0097] Place the alumina crucible containing the ceramic green body in a box furnace and heat the box furnace to 600 - 700°C at a heating rate of 2 - 5°C / min, hold for 3 h to remove the binder from the ceramic green body. After the holding is completed, cool it to room temperature with the furnace to obtain the ceramic green body after debinding.

[0098] Table 6 Process parameters of each example in Step 6

[0099]

[0100] Step 7, Sintering:

[0101] Place the obtained green ceramic body in an alumina crucible and put it into a box furnace. Heat the box furnace to 1050 - 1200 °C at a heating rate of 2 - 5 °C / min and hold for 2 - 4 h to sinter the green ceramic body. After the holding is completed, cool it to 500 °C at a rate of 5 - 10 °C / min and then cool it to room temperature with the furnace.

[0102] Table 7 Process parameters of each example in Step 7

[0103]

[0104] Take out the sintered green ceramic body, grind and polish it to obtain the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material Ca 0.97 (Na 0.5 Nd 0.5 ) 0.03 Bi4Ti4O 15 .

[0105] The phase structure determination of the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material obtained by the present invention:

[0106] Perform phase analysis of the piezoelectric ceramic material using X-ray diffraction. The instrument used is the X’Pert PRO diffractometer of the Dutch Analytical Instrument Company. Its scanning angle range is 2θ = 20 - 90°, the scanning speed is 5° / min, and the step size is 0.01°. The obtained ceramic diffraction results are as Figure 1 .

[0107] The determination of the microstructure and element distribution of the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material:

[0108] Observe the Na, Nd co-doped CaBi4Ti4O 15 piezoelectric ceramic material Ca 0.97 (Na 0.5 Nd 0.5 ) 0.03 Bi4Ti4O 15 , Ca 0.94 (Na 0.5 Nd 0.5 ) 0.06 Bi4Ti4O 15 , Ca 0.91 (Na 0.5 Nd 0.5 ) 0.09 Bi4Ti4O15 , Ca 0.88 (Na 0.5 Nd 0.5 ) 0.12 Bi4Ti4O 15 Microscopic morphology of the surface of the ceramic sample after grinding, polishing and thermal corrosion.

[0109] CaBi4Ti4O co-doped with Na and Nd 15 Measurement of the resistivity of the piezoelectric ceramic material:

[0110] Connect a Changzhou Tonghui TH2683 insulation resistance tester to a high-temperature box furnace to directly measure the resistance value R of the material at different temperatures. According to the calculation formula of resistivity ρ = RS / l, the resistivity ρ is obtained, where S is the electrode area of the sample and l is the thickness of the sample. The size of the sample is Φ12mm × lmm, and the electrode area is 50.26mm 2

[0111] CaBi4Ti4O co-doped with Na and Nd 15 Measurement of the dielectric temperature spectrum of the piezoelectric ceramic material:

[0112] Use an Agilent E4980A digital bridge from the United States and a DMS-2000 high and low temperature dielectric temperature spectrum measurement system from Wuhan Bilibo Co., Ltd. to test the capacitance value C and dielectric loss tanδ of the sample, and the heating rate is 3°C / min.

[0113] CaBi4Ti4O co-doped with Na and Nd 15 Measurement of the piezoelectric constant of the piezoelectric ceramic material:

[0114] Before testing the piezoelectric properties, the sample needs to be poled. The poling process is as follows: Grind the ceramic wafer and clean it ultrasonically. After coating the surface with silver, place it in silicone oil at 150°C and apply an electric field of 8 kV / mm for 20 min for poling. After the poled sample is left standing for 24 h, use a JZ-4AN type d 33 Quasi-static tester to test the piezoelectric constant of the ceramic sample.

[0115] CaBi4Ti4O co-doped with Na and Nd 15 The dielectric properties, piezoelectric properties and resistivity of the piezoelectric ceramic material are listed in Table 8.

[0116] Table 8 CaBi4Ti4O co-doped with Na and Nd 15 Electrical properties of the piezoelectric ceramic material

[0117] Curie temperature / °C <![CDATA[Piezoelectric constant / pC·N -1 > Resistivity / Ω·cm (600 °C) Dielectric loss (600 °C) x＝0.03 769 13 <![CDATA[2.1×10 6 > 0.2472 x＝0.06 767 21 <![CDATA[5×10 6 > 0.0807 x＝0.09 763 24 <![CDATA[5.6×10 6 > 0.0491 x＝0.12 751 16 <![CDATA[5.1×10 6 > 0.0088

Claims

1. A Na and Nd co-doped CaBi4Ti4O 15 A piezoelectric ceramic material, characterized in that CaBi4Ti4O 15 The chemical composition of piezoelectric ceramic materials is Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 , where x = 0.03~0.

12.

2. The Na- and Nd-co-doped CaBi4Ti4O as claimed in claim 1 15 A piezoelectric ceramic material, characterized in that Generate the Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 The raw materials are CaCO3, Bi2O3, TiO2, NaCO3 and Nd2O3, all of which are analytically pure and have a particle size of micron level.

3. The Na- and Nd-co-doped CaBi4Ti4O as claimed in claim 1 15 A method for preparing a piezoelectric ceramic material, characterized in that: The specific process is: Step 1, Ingredients: According to Ca 1-x (Na 0.5 Nd 0.5 ) x Bi4Ti4O 15 Weigh the initial raw materials CaCO3, SrCO3, BaCO3, PbO, Bi2O3 and TiO2 in the stoichiometric ratio of the chemical formula; Step 2, preparing mixed powder: Add anhydrous ethanol to the weighed initial raw materials, mix, and then ball-mill for 8 to 12 hours to obtain a mixture; dry the obtained mixture to obtain a mixed powder; Step 3, preparing pre-synthesized powder: Placing the obtained mixed powder in a pre-sintering furnace; pre-sintering the mixed powder to obtain pre-synthesized powder; Step 4, ball milling: Adding anhydrous ethanol to the obtained pre-synthesized powder; ball milling for 8 to 12 hours and then drying to obtain the pre-synthesized powder; Step 5, granulation and tableting: Adding a PVA aqueous solution to the pre-synthesized powder obtained after secondary ball milling, and the mass ratio of the PVA aqueous solution to the pre-synthesized powder is 1:5; mixing evenly and sieving to obtain microparticles; placing the obtained microparticles in a tablet press to obtain a ceramic body; Step 6, preparing a ceramic body: The ceramic body is placed in an alumina crucible; the alumina crucible containing the ceramic body is placed in a box furnace to debind the ceramic body; after the heat preservation is completed, the ceramic body is cooled to room temperature in the furnace to obtain a debinded ceramic body; Step 7, sintering: The obtained ceramic green body is placed in an alumina crucible and placed in a box furnace; and the ceramic green body is sintered; The sintered ceramic body was taken out and polished to obtain Na and Nd co-doped CaBi4Ti4O 15 Piezoelectric ceramic materials.

4. The preparation method according to claim 3, characterized in that: When preparing the mixed powder, the mass ratio of the anhydrous ethanol to the initial raw material is 1:1; the drying temperature is 50-80° C., and the drying time is 12 hours.

5. The preparation method according to claim 3, characterized in that: When preparing the pre-synthesized powder, the pre-sintering temperature is 800-950° C., and the holding time is 4 hours; after the holding time is completed, the temperature is lowered to 500° C. at a rate of 5-10° C. / min, and then cooled to room temperature along with the furnace.

6. The preparation method according to claim 5, characterized in that: The heating rate of the pre-firing furnace is 5-10°C / min.

7. The preparation method according to claim 3, characterized in that: During ball milling, the mass ratio of the anhydrous ethanol to the powder is 1:

1.

8. The preparation method according to claim 3, characterized in that: During granulation and tableting, the concentration of the PVA aqueous solution is 5wt.%, the particle size of the microparticles is 50-100 meshes, and the tableting pressure is 2-5MPa.

9. The preparation method according to claim 3, characterized in that: When preparing the ceramic green body, the temperature of the box-type furnace is 600-700° C. and the temperature is kept for 3 hours; the heating rate of the box-type furnace is 2-5° C. / min.

10. The preparation method according to claim 3, characterized in that: During sintering, the temperature of the box furnace is 1050-1200°C, and the insulation time is 2-4h; the heating rate of the box furnace is 2-5°C / min; after the insulation is completed, the box furnace is cooled to 500°C at a rate of 5-10°C / min; and cooled to room temperature along with the furnace.

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