Calcium bismuth titanate-based ferroelectric ceramic material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of ferroelectric ceramic manufacturing, in particular to a calcium bismuth titanate based ferroelectric ceramic material and a preparation method and application thereof. The chemical formula of the calcium bismuth titanate-based ferroelectric ceramic material is CaBi4-xRxTi4O15-yMnO2, R is one or more of lanthanide rare earth elements, in the formula, x is more than 0 and less than or equal to 0.2, and y is more than or equal to 0.1 wt% and less than or equal to 0.5 wt%. The calcium bismuth titanate-based ferroelectric ceramic material disclosed by the invention has the original ferroelectric, piezoelectric and dielectric properties, also has a photoluminescence characteristic, and belongs to a novel multifunctional material. The ceramic material has excellent photoelectric properties, and has wide application prospects in the fields of photoelectric integration, micro electro mechanical system, photoelectric sensing, LED technology and the like.

Description

Technical Field

[0001] This invention relates to the field of ferroelectric ceramic manufacturing technology, and in particular to a bismuth calcium titanate-based ferroelectric ceramic material, its preparation method, and its application. Background Technology

[0002] Multiferroic materials are an important field of ceramic materials. They have attracted widespread attention from researchers because they possess two or more properties such as ferromagnetism or antiferromagnetism, ferroelectricity and ferroelasticity. They have wide applications in photovoltaics, sensors, memory, optics and electronics.

[0003] Bismuth layered ferroelectrics possess advantages such as low dielectric constant, high Curie temperature, and good resistance to polarization fatigue, making them a promising candidate for high-temperature piezoelectric and non-volatile memory applications. The general chemical formula for bismuth layered ferroelectrics is (Bi₂O₂). 2+ (A m-1 B m O 3m+1 ) 2− In this system, A represents monovalent, divalent, or trivalent ions with larger ionic radii, while B represents tetravalent or pentavalent ions with smaller ionic radii. The integer m ranges from 2 to 5. CaBi₄Ti₄O 15 (Hereinafter referred to as CBT) is a typical Aurivillius ferroelectric material with m=4, where the A site is formed by Ca 2+ and Bi 3+ Ionic composition, with Ti at the B site 4+ Ion occupation. The original CBT is reported to have a fairly high Curie point (T0). C Its high temperature (790℃) and excellent ferroelectric properties make it one of the most noteworthy ferroelectric materials.

[0004] However, the performance development and modification of CBT materials are still not perfect. Since the A-site and B-site of CBT materials have different chemical valence states, the doping sites are limited by the high and low valence of the doping elements. Although existing technologies can dop CBT materials by single A-site or B-site doping, single doping is difficult to completely solve the need to improve ferroelectric and piezoelectric properties.

[0005] Therefore, there is still a lack of research on composite doping of CBT materials to comprehensively improve the ferroelectric and piezoelectric properties of bismuth calcium titanate-based ferroelectric ceramics. Summary of the Invention

[0006] This invention provides a bismuth calcium titanate-based ferroelectric ceramic material, its preparation method, and its applications. The aim is to achieve synergistic effects by combining rare earth ions and Mn ions to realize A / B site composite doping. This reduces the impact of oxygen vacancies and other defects on the ceramic material's properties, improving resistivity and polarization intensity. Furthermore, it refines the grain size and homogenizes the ceramic microstructure. This is beneficial for comprehensively improving the ferroelectric and piezoelectric properties of bismuth calcium titanate-based ferroelectric ceramics.

[0007] To achieve the above objectives, the present invention provides a bismuth calcium titanate-based ferroelectric ceramic material, wherein the chemical formula of the bismuth calcium titanate-based ferroelectric ceramic material is CaBi. 4-x R x Ti4O 15 -yMnO2, where R is one or more of the lanthanide rare earth elements, and 0 < x ≤ 0.2, 0.1 wt% ≤ y ≤ 0.5 wt%.

[0008] Based on the doping location, CBT systems can be classified into A-site doping, B-site doping, A / B-site composite doping, and additive modification. A-site doping primarily uses lanthanide rare earth elements (such as La). 3+ Ce 3+ Pr 3+ 、Nd 3+ 、Sm 3+ Dy 3+ A total of 17 elements (including [elements not specified]) were used to dope and replace Bi at the A site of BLSF ceramic materials. 3+ Ions, due to Bi 3+ Ions are highly volatile during high-temperature sintering, forming oxygen vacancies and affecting the electrical properties of ceramics. Therefore, this doping substitution method can effectively reduce Bi content. 3+ The volatilization of oxygen vacancies reduces the formation of oxygen vacancies, thereby improving electrical properties to varying degrees. Bore doping is another effective method to improve the electrical properties of ceramics. Elements or composite elements with ionic radii similar to those at the bore site are selected, such as Mo, W, Nb, Ta, V, Nb / Mn, Ta / Mn, W / Cr, and Nb / Mg. Bore doping has a relatively small effect on the Curie temperature, but it can significantly improve ferroelectric and piezoelectric properties.

[0009] Due to manganese ions (Mn 2+ Mn 3+ and Mn 4+The multivalent nature of ions allows for changes in ionic valence states that can compensate for charge loss and reduce the concentration of oxygen vacancies in the ceramic, thereby increasing the ceramic microstructure density and reducing charge carrier movement, thus refining the grain size. Meanwhile, Bi volatilization is a common problem in BLSF materials during high sintering temperatures (typically above 800 °C), which may induce Bi vacancies. Manganese ions exhibit different valence states at different temperatures (generally decreasing at high temperatures), with Mn ions exhibiting Mn... 3+ and Mn 2+ Isochemical state, and preferentially Mn 3+ Valence state, ion size and T i4+ Therefore, Mn ions readily enter the B site to substitute for Ti. 4+ (Ti) 4+ :ri = 0.605 Å, Mn 4+ :ri=0.53 Å, Mn 3+ :ri = 0.58 Å, Mn 2+ :ri = 0.96 Å), and this substitution does not lead to large lattice distortion; Mn under high sintering temperature conditions 4+ Ions reduced to Mn 3+ or Mn 2+ Reduced Mn ions can capture weakly bonded electrons to reduce leakage losses, thereby improving polarization behavior and enhancing piezoelectric properties.

[0010] The bismuth titanate calcium-based ferroelectric ceramic material provided by this invention has the chemical formula CaBi. 4-x R x Ti4O 15 The material is doped with both rare earth elements and MnO2. Rare earth ions act as A-site dopant, while Mn ions act as B-site dopant after the introduction of MnO2, achieving A / B site composite doping. This synergistic effect increases the distortion of oxygen octahedrons and improves domain orientation, thus enhancing the electrical properties of the ceramic. This not only combines the advantages of individual A-site doping and individual B-site doping, but also improves the piezoelectric activity, remanent polarization, and fatigue resistance of the material, as well as the resistivity, without significantly reducing the Curie temperature Tc.

[0011] Furthermore, the CBT ceramic selected in this invention has a four-layer bismuth layered structure and contains a large amount of Bi. 3+ The Curie temperature (Tc) of CBT ceramics is approximately 790 °C. However, A-site doping typically leads to a decrease in the Curie temperature. CBT ceramics, which inherently have a high Curie temperature, can maintain a high Curie temperature while improving piezoelectric properties, and they also contain a large amount of Bi. 3+ The characteristics of ions also necessitate doping modification to achieve better doping effects.

[0012] Preferably, R is one or more of Sm, Y, Eu, Nd, Ce or La;

[0013] The bismuth calcium titanate-based ferroelectric ceramic material uses layered bismuth calcium titanate as a matrix and is doped with rare earth elements and MnO2; wherein rare earth elements are doped at the A site in the layered bismuth calcium titanate, and Mn ions are doped at the B site in the layered bismuth calcium titanate.

[0014] Under the same technical concept, the present invention also provides a method for preparing the aforementioned bismuth titanate calcium-based ferroelectric ceramic material, comprising the following steps:

[0015] (1) Ingredients: Weigh and mix calcium carbonate, bismuth oxide, titanium oxide and rare earth element source to obtain mixed powder;

[0016] (2) First ball milling: The mixed powder from step (1) is ball milled once;

[0017] (3) Drying and pre-firing: The mixed slurry after ball milling in step (2) is dried and ground, and then compacted and pre-firing. The pre-firing is heated to 600-850 ℃ at a heating rate of 5-10 ℃ / min and kept at this temperature for 0.5-4h.

[0018] (4) Secondary ball milling: Cool the powder after pre-calcination in step (3), add manganese oxide and perform secondary ball milling;

[0019] (5) Drying and granulation: The mixed slurry after the second ball milling in step (4) is dried and ground. The obtained powder is granulated by adding PVA solution and 0.1-0.4 mL / g anhydrous ethanol and then sieved.

[0020] (6) Pressing and sintering: Press the sieved powder in step (5) into a ceramic green body, remove the binder from the green body and sinter it to obtain a bismuth calcium titanate-based ferroelectric ceramic material.

[0021] The preparation method of bismuth calcium titanate ferroelectric ceramic material is a solid-state reaction. One or more lanthanide rare earth elements are added to the bismuth calcium titanate ceramic material matrix for A-site doping, and 0.2 wt% MnO2 is added during two-ball milling for modification treatment to obtain bismuth calcium titanate ceramic with better ferroelectric properties.

[0022] In the sintering process, MnO2 not only acts as a dopant but also as a sintering aid. On one hand, MnO2 can coat ceramic grains, controlling excessively rapid and large grain growth, achieving grain refinement and size homogenization. Appropriate coating phases contribute to the densification of the ceramic structure. On the other hand, trace doping can replace a small number of lattice site atoms, inducing lattice distortion, affecting grain growth, and increasing the resistivity of piezoelectric materials. High-resistivity ceramics can be subjected to highly polarized electric fields, resulting in more complete polarization of ferroelectric ceramics. Simultaneously, lattice distortion also increases crystal asymmetry, reduces the coercive field, makes domain rotation easier, enhances spontaneous polarization, and increases remanent polarization intensity, thus comprehensively improving both ferroelectric and piezoelectric properties.

[0023] Meanwhile, rare earth ion doping replaced Bi. 3+ Ions, reducing Bi 3+ The volatilization of rare earth ions reduces the formation of oxygen vacancies; the combined effect of rare earth ions and MnO2 makes grain growth more controllable during sintering, reduces sintering porosity, and achieves grain refinement and ceramic microstructure homogenization. The reduced internal porosity of the ceramic makes it more compact. Compacted ceramics have relatively fewer internal defects and can withstand higher breakdown field strengths, which is beneficial for obtaining excellent electrical properties.

[0024] On the other hand, the two-stage sintering process of pre-firing and formal sintering designed in this application, in conjunction with the doping process, has the following objectives: (1) To control volatilization and stabilize the composition. Manganese oxide is relatively unstable at high temperatures. If it is added during the first high-temperature pre-firing, a large amount of manganese will be lost during the long holding process, which will not achieve the effect and significance of introducing the element; (2) To give full play to the "sintering aid" role of manganese. Manganese oxide is a very effective sintering aid, especially in electronic ceramics. It can form a liquid phase at a relatively low temperature and greatly promote the densification of ceramics through the liquid phase sintering mechanism. This effect is best achieved in the second sintering (final firing) after the ceramic particles have been initially formed (after pre-firing).

[0025] Preferably, the rare earth element source in step (1) is one or more of the oxides or nitrates of lanthanide rare earth elements; the content ratio of calcium carbonate, bismuth oxide, titanium oxide and rare earth element source is based on the chemical formula CaBi 4- x R x Ti4O 15 -yMnO2, 0<x≤0.2 are used for design;

[0026] Preferably, in steps (2) and (4), the first and second ball milling uses zirconia balls as the ball milling medium and anhydrous ethanol is added. The volume ratio of zirconia balls to raw materials is 1-2:1, and the volume ratio of zirconia balls to ethanol is 1:1-2. The ball milling time is 2-12 hours, and the rotation speed is 200-500 rpm.

[0027] Preferably, the drying and grinding in steps (3) and (5) involves pouring the mixed slurry into a petri dish and drying it in a constant temperature oven for 6-24 hours to remove anhydrous ethanol, and then grinding the resulting powder into powder in a mortar; the compaction and pre-firing in step (3) involves compaction and sealing in an alumina crucible and pre-firing in a muffle furnace.

[0028] Preferably, in step (4), the addition of manganese oxide for secondary ball milling is performed, and the mass of the added manganese oxide is 0.1-0.5 wt% of the mass of the pre-calcined powder.

[0029] Preferably, the granulation in step (5) specifically includes: weighing the dried and ground powder, adding a 5-8 wt% PVA solution at a ratio of 0.05-0.20 mL per gram of powder, and adding 0.1-0.4 mL / g of anhydrous ethanol, mixing evenly in a mortar; the sieving is performed using an 80-mesh sieve. The ethanol content may have a certain impact on the granulation result, and the quality of granulation is directly related to the dense sintering of ceramics, thus affecting the performance of ceramics.

[0030] Preferably, the pressing in step (6) specifically includes: taking the sieved powder from step (5) and holding it under a pressure of 50-200 MPa for 1-5 minutes to press it into a ceramic green body with a thickness of 10-14 mm;

[0031] The debinding process specifically includes: placing the ceramic green body in an alumina crucible and then into a muffle furnace, filling and sealing it with the sieved powder from step (5), raising the temperature at a rate of 1-2℃ / min, raising it to 500-700℃ and holding it for 1-4 hours to remove the organic binder.

[0032] Preferably, the sintering in step (6) specifically includes: after debinding, continuing to heat up at a rate of 5-10℃ / min, raising the temperature to 900-1200℃, and holding for 1-2 hours to obtain bismuth calcium titanate-based ferroelectric ceramic material.

[0033] Under the same technical concept, the present invention also provides an application of the bismuth calcium titanate-based ferroelectric ceramic material or the bismuth calcium titanate-based ferroelectric ceramic material prepared by the preparation method, wherein the bismuth calcium titanate-based ferroelectric ceramic material is polished to a thickness of 0.4-0.7 mm, ultrasonically cleaned with ethanol and dried, screen-printed with silver electrodes, and then fired with silver to obtain the finished ferroelectric ceramic product.

[0034] The above-described solution of the present invention has the following beneficial effects:

[0035] (1) The bismuth-calcium titanate-based ferroelectric ceramic material of the present invention, while possessing the original ferroelectric, piezoelectric and dielectric properties, also exhibits photoluminescence properties, making it a novel multifunctional material. This ceramic material has excellent photoelectric properties and has broad application prospects in optoelectronic integration, microelectromechanical systems, optoelectronic sensing, LED technology and other fields;

[0036] (2) The bismuth calcium titanate-based ferroelectric ceramic material of the present invention achieves dual doping of rare earth elements and MnO2. Based on the temperature properties and element content characteristics of CBT, rare earth ions are designed as A-site doping. After the introduction of MnO2, Mn ions can be used as B-site doping to achieve A / B-site composite doping, which has a synergistic effect, increases the distortion of oxygen octahedrons, improves domain orientation, and can better improve the electrical performance of ceramics.

[0037] (3) In the preparation method of the bismuth calcium titanate-based ferroelectric ceramic material of the present invention, double doping and step-by-step grinding, pre-sintering and sintering were carried out to achieve double doping modification. MnO2 not only acts as a doping additive during the sintering process, but also plays the role of sintering aid. It can coat the ceramic grains, control the grains to grow too fast and too large, and achieve grain refinement and size homogenization. The trace doping of MnO2 and rare earth elements can replace a small number of lattice site atoms, induce lattice distortion, affect grain growth, increase the resistivity of piezoelectric materials, reduce the internal porosity of ceramics, make ceramics more compact, and benefit the acquisition of excellent electrical properties. Attached Figure Description

[0038] Figure 1 The image shows the XRD pattern of the calcium titanate-based ferroelectric ceramic material doped with rare earth element Y in Example 1 of this invention.

[0039] Figure 2 The image shows the XRD pattern of the calcium titanate-based ferroelectric ceramic material doped with Eu as a rare earth element in Example 2 of this invention.

[0040] Figure 3 The images show SEM images of the undoped CBT material and the bismuth calcium titanate-based ferroelectric ceramic material doped with rare earth elements Eu and Y in Examples 1 and 2 of this invention; where (a) is the undoped CBT material, (b) is the bismuth calcium titanate-based ferroelectric ceramic material doped with rare earth element Eu, and (c) is the bismuth calcium titanate-based ferroelectric ceramic material doped with rare earth element Y.

[0041] Figure 4 The hysteresis loop at room temperature of the bismuth titanate calcium-based ferroelectric ceramic material doped with rare earth element Y in Example 1 of this invention;

[0042] Figure 5 This is the hysteresis loop at room temperature of the bismuth titanate calcium-based ferroelectric ceramic material doped with Eu as a rare earth element in Example 2 of the present invention. Detailed Implementation

[0043] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0044] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a locking connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] Example 1:

[0048] The stoichiometric formula for calcium bismuth titanate-based ferroelectric ceramics is: CaBi 4-x Y x Ti4O 15 -yMnO2, where x = 0.09, y = 0.2 wt%, this material is Y / Mn doped modified bismuth titanate (CaBi4Ti4O2). 15 Ferroelectric ceramics. Using layered bismuth calcium titanate as the matrix, Y element is doped at the A-site in the layered bismuth calcium titanate, and Mn ions are doped at the B-site in the layered bismuth calcium titanate. Figure 1 The image shows the XRD pattern of the calcium titanate-based ferroelectric ceramic material doped with rare earth element Y in Example 1 of this invention.

[0049] The preparation process of this bismuth titanate calcium-based ferroelectric ceramic material is as follows:

[0050] Step 1, according to the stoichiometric formula: CaBi 4-x Y x Ti4O 15 -yMnO2, where x = 0.09, various raw materials (calcium carbonate CaCO3, bismuth oxide Bi2O3, titanium oxide TiO2, and yttrium nitrate hexahydrate Y(NO3)3·6H2O added as shown in Table 1) were weighed and placed in a polytetrafluoroethylene ball mill jar. Anhydrous ethanol was used as the dispersion medium, with a volume ratio of ethanol to raw materials of 2:1. The volume ratio of zirconia balls to raw materials was 1:1. The mixture was ball-milled for 6 hours using a planetary mill at a speed of 350 rpm. The slurry was poured into a petri dish and placed in a constant temperature oven at 80℃ for 6 hours to remove anhydrous ethanol. The resulting powder was ground into powder in a mortar and then placed in an alumina crucible and sealed in a muffle furnace for pre-calcination. The temperature was increased to 850℃ at a heating rate of 5-10℃ / min and held for 2 hours to obtain pre-sintered powder.

[0051] Step 2: Cool the pre-sintered powder and place it together with 0.2 wt% MnO2 in a polytetrafluoroethylene ball mill jar for a second ball milling. The ball milling parameters are the same as the first ball milling. Take out the ball milled material and dry it. The drying parameters are the same as the first time. Add 8 wt% PVA aqueous solution as a binder. The mass of PVA aqueous solution is 10% of the total mass. At the same time, add 0.2 mL / g ethanol and mix it evenly in a mortar. After passing it through an 80-mesh sieve, press the resulting powder into a green embryo with a diameter of 13 mm under a pressure of 100 MPa for 2 min.

[0052] Step 3: Place the green blank in an alumina crucible and put it into a muffle furnace. Increase the temperature to 600℃ at 2℃ / min and hold for 2 hours to remove PVA. Then continue to heat the green blank at a rate of 5-10℃ / min and sinter at 1100℃ for 2 hours to obtain bismuth calcium titanate-based ferroelectric ceramic material.

[0053] Step 4: Polish both sides of the sintered bismuth calcium titanate-based ferroelectric ceramic material to a thickness of 0.5 mm, ultrasonically clean with ethanol and dry, screen print silver electrodes, and then sinter the electrodes at 900℃ for 20 min to obtain the finished ferroelectric ceramic product.

[0054] The ferroelectric properties of the bismuth calcium titanate-based ferroelectric ceramic material obtained in this embodiment are as follows: Ps = 10.59 μC / cm 2 Pr = 1.38 μC / cm 2 .

[0055] Example 2

[0056] The stoichiometric formula for calcium bismuth titanate-based ferroelectric ceramics is: CaBi 4-x Eux Ti4O 15 -yMnO2, where x = 0.09, y = 0.2 wt%, this material is Eu / Mn doped modified bismuth titanate (CaBi4Ti4O2). 15 Ferroelectric ceramics. Using layered bismuth calcium titanate as the matrix, Eu is doped at the A-site in the layered bismuth calcium titanate, and Mn ions are doped at the B-site in the layered bismuth calcium titanate. Figure 2 The image shows the XRD pattern of the calcium titanate-based ferroelectric ceramic material doped with Eu as a rare earth element in Example 2 of this invention.

[0057] The preparation process of this bismuth titanate calcium-based ferroelectric ceramic material is as follows:

[0058] Step 1, according to the stoichiometric formula: CaBi 4-x Eu x Ti4O 15 -yMnO2, where x=0.09, y=0.2 wt%, various raw materials (calcium carbonate CaCO3, bismuth oxide Bi2O3, titanium oxide TiO2, europium nitrate hexahydrate Eu(NO3)3·6H2O added as shown in Table 1) were weighed and placed in a polytetrafluoroethylene ball mill jar. Anhydrous ethanol was used as the dispersion medium, with a volume ratio of ethanol to raw materials of 2:1. The volume ratio of zirconia balls to raw materials was 1:1. The mixture was ball-milled for 6 hours using a planetary mill at a speed of 350 rpm. The slurry was poured into a petri dish and placed in a constant temperature oven at 80℃ for 6 hours to remove anhydrous ethanol. The resulting powder was ground into powder in a mortar and then placed in an alumina crucible and sealed in a muffle furnace for pre-calcination. The temperature was increased to 850℃ at a heating rate of 5-10℃ / min and held for 2 hours to obtain pre-sintered powder.

[0059] Step 2: Cool the pre-sintered powder and place it together with 0.2% of its mass of MnO2 into a polytetrafluoroethylene ball mill jar for a second ball milling. The ball milling parameters are the same as the first ball milling. Take out the ball milled material and dry it. The drying parameters are the same as the first time. Add 8 wt% PVA aqueous solution as a binder. The mass of PVA aqueous solution is 10% of the total mass. At the same time, add 0.2 mL / g ethanol and mix it evenly in a mortar. After passing it through an 80-mesh sieve, press it into a green embryo with a diameter of 13 mm under a pressure of 100 MPa for 2 min.

[0060] Step 3: Place the green blank in an alumina crucible and put it into a muffle furnace. Increase the temperature to 600℃ at 2℃ / min and hold for 2 hours to remove PVA. Then continue to heat the green blank at a rate of 5-10℃ / min and sinter at 1100℃ for 2 hours to obtain bismuth calcium titanate-based ferroelectric ceramic material.

[0061] Step 4: The sintered bismuth calcium titanate-based ferroelectric ceramic material is polished on both sides to a thickness of 0.5 mm, ultrasonically cleaned with ethanol, dried, and then silver electrodes are screen-printed. The electrodes are then sintered at 900℃ for 20 minutes to obtain the finished ferroelectric ceramic product. The ferroelectric properties of the bismuth calcium titanate-based ferroelectric ceramic material obtained in this example are as follows: Ps = 13.1 μC / cm². 2 Pr = 3.47 μC / cm 2 .

[0062] Figure 3 The images show SEM images of the undoped CBT material and the bismuth titanate calcium-based ferroelectric ceramic material doped with rare earth elements Eu and Y in Examples 1 and 2 of this invention. Figure 4 The hysteresis loop at room temperature of the bismuth titanate calcium-based ferroelectric ceramic material doped with rare earth element Y in Example 1 of this invention; Figure 5 This is the hysteresis loop at room temperature of the bismuth titanate calcium-based ferroelectric ceramic material doped with Eu as a rare earth element in Example 2 of the present invention.

[0063] Example 3

[0064] The stoichiometric formula for calcium bismuth titanate-based ferroelectric ceramics is: CaBi 4-x Y x Ti4O 15 -yMnO2, where x = 0.09, y = 0.5 wt%, this material is pure phase bismuth titanate (CaBi4Ti4O) 15 Ferroelectric ceramics. Using layered bismuth calcium titanate as the matrix, Y element is doped at the A-site in the layered bismuth calcium titanate, and Mn ions are doped at the B-site in the layered bismuth calcium titanate.

[0065] The preparation process of this bismuth titanate calcium-based ferroelectric ceramic material is as follows:

[0066] Step 1, according to the stoichiometric formula: CaBi 4-x Y x Ti4O 15-yMnO2, where x=0.09, y=0.5 wt%, various raw materials (calcium carbonate CaCO3, bismuth oxide Bi2O3, titanium oxide TiO2 and yttrium nitrate hexahydrate Y(NO3)3·6H2O added as shown in Table 1) were weighed and placed in a polytetrafluoroethylene ball mill jar. Anhydrous ethanol was used as the dispersion medium, with a volume ratio of ethanol to raw materials of 2:1. The volume ratio of zirconia balls to raw materials was 1:1. The mixture was ball-milled for 6 hours using a planetary mill at a speed of 350 rpm. The slurry was poured into a petri dish and placed in a constant temperature oven at 80℃ for 6 hours to remove anhydrous ethanol. The resulting powder was ground into powder in a mortar and then placed in an alumina crucible and sealed in a muffle furnace for pre-calcination. The temperature was increased to 850℃ at a heating rate of 5-10℃ / min and held for 2 hours to obtain pre-sintered powder.

[0067] Step 2: Cool the pre-sintered powder and place it together with 0.2 wt% MnO2 in a polytetrafluoroethylene ball mill jar for a second ball milling. The ball milling parameters are the same as the first ball milling. Take out the ball milled material and dry it. The drying parameters are the same as the first time. Add 8 wt% PVA aqueous solution as a binder. The mass of PVA aqueous solution is 10% of the total mass. At the same time, add 0.2 mL / g ethanol and mix it evenly in a mortar. After passing it through an 80-mesh sieve, press the resulting powder into a green embryo with a diameter of 13 mm under a pressure of 100 MPa for 2 min.

[0068] Step 3: Place the green blank in an alumina crucible and put it into a muffle furnace. Increase the temperature to 600℃ at 2℃ / min and hold for 2 hours to remove PVA. Then continue to heat the green blank at a rate of 5-10℃ / min and sinter at 1100℃ for 2 hours to obtain bismuth calcium titanate-based ferroelectric ceramic material.

[0069] Step 4: The sintered bismuth calcium titanate-based ferroelectric ceramic material is polished on both sides to a thickness of 0.5 mm, ultrasonically cleaned with ethanol, dried, and then silver electrodes are screen-printed. The electrodes are then sintered at 900℃ for 20 minutes to obtain the finished ferroelectric ceramic product. The ferroelectric properties of the bismuth calcium titanate-based ferroelectric ceramic material obtained in this example are as follows: Ps = 10.31 μC / cm². 2 Pr = 1.26 μC / cm 2 .

[0070] Example 4

[0071] The stoichiometric formula for calcium bismuth titanate-based ferroelectric ceramics is: CaBi 4-x Eu x Ti4O 15 -yMnO2, where x = 0.15, y = 0.2 wt%, this material is Eu / Mn doped modified bismuth titanate (CaBi4Ti4O2). 15Ferroelectric ceramics. Using layered bismuth calcium titanate as the matrix, Eu is doped at the A-site in the layered bismuth calcium titanate, and Mn ions are doped at the B-site in the layered bismuth calcium titanate.

[0072] The preparation process of this bismuth titanate calcium-based ferroelectric ceramic material is as follows:

[0073] Step 1, according to the stoichiometric formula: CaBi 4-x Eu x Ti4O 15 -yMnO2, where x=0.15, y=0.2 wt%, various raw materials (calcium carbonate CaCO3, bismuth oxide Bi2O3, titanium oxide TiO2, europium nitrate hexahydrate Eu(NO3)3·6H2O added as shown in Table 1) were weighed and placed in a polytetrafluoroethylene ball mill jar. Anhydrous ethanol was used as the dispersion medium, with a volume ratio of ethanol to raw materials of 2:1. The volume ratio of zirconia balls to raw materials was 1:1. The mixture was ball-milled for 6 hours using a planetary mill at a speed of 350 rpm. The slurry was poured into a petri dish and placed in a constant temperature oven at 80℃ for 6 hours to remove anhydrous ethanol. The resulting powder was ground into powder in a mortar and then placed in an alumina crucible and sealed in a muffle furnace for pre-calcination. The temperature was increased to 850℃ at a heating rate of 5-10℃ / min and held for 2 hours to obtain pre-sintered powder.

[0074] Step 2: Cool the pre-sintered powder and place it together with 0.2 wt% MnO2 in a polytetrafluoroethylene ball mill jar for a second ball milling. The ball milling parameters are the same as the first ball milling. Take out the ball milled material and dry it. The drying parameters are the same as the first time. Add 8 wt% PVA aqueous solution as a binder. The mass of PVA aqueous solution is 10% of the total mass. At the same time, add 0.2 mL / g ethanol and mix it evenly in a mortar. After passing it through an 80-mesh sieve, press the resulting powder into a green embryo with a diameter of 13 mm under a pressure of 100 MPa for 2 min.

[0075] Step 3: Place the green blank in an alumina crucible and put it into a muffle furnace. Increase the temperature to 600℃ at 2℃ / min and hold for 2 hours to remove PVA. Then continue to heat the green blank at a rate of 5-10℃ / min and sinter at 1100℃ for 2 hours to obtain bismuth calcium titanate-based ferroelectric ceramic material.

[0076] Step 4: The sintered bismuth calcium titanate-based ferroelectric ceramic material is polished on both sides to a thickness of 0.5 mm, ultrasonically cleaned with ethanol, dried, and then silver electrodes are screen-printed. The electrodes are then sintered at 900℃ for 20 minutes to obtain the finished ferroelectric ceramic product. The ferroelectric properties of the bismuth calcium titanate-based ferroelectric ceramic material obtained in this example are as follows: Ps = 11.64 μC / cm 2 Pr = 2.69 μC / cm 2 .

[0077] Example 5

[0078] The stoichiometric formula for calcium bismuth titanate-based ferroelectric ceramics is: CaBi 4-x Ce x Ti4O 15 -yMnO2, where x = 0.09, y = 0.2 wt%, this material is Ce / Mn doped modified bismuth titanate (CaBi4Ti4O2). 15 Ferroelectric ceramics. Using layered bismuth calcium titanate as the matrix, Ce is doped at the A-site in the layered bismuth calcium titanate, and Mn ions are doped at the B-site in the layered bismuth calcium titanate.

[0079] The preparation process of this bismuth titanate calcium-based ferroelectric ceramic material is as follows:

[0080] Step 1, according to the stoichiometric formula: CaBi 4-x Ce x Ti4O 15 -yMnO2, where x=0.09, y=0.2 wt%, various raw materials (calcium carbonate CaCO3, bismuth oxide Bi2O3, titanium oxide TiO2, cerium nitrate hexahydrate Ce(NO3)3·6H2O added as shown in Table 1) were weighed and placed in a polytetrafluoroethylene ball mill jar. Anhydrous ethanol was used as the dispersion medium, with a volume ratio of ethanol to raw materials of 2:1. The volume ratio of zirconia balls to raw materials was 1:1. The mixture was ball-milled for 6 hours using a planetary mill at a speed of 350 rpm. The slurry was poured into a petri dish and dried in a constant temperature oven at 80℃ for 6 hours to remove anhydrous ethanol. The resulting powder was ground into powder in a mortar and then placed in an alumina crucible and sealed in a muffle furnace for pre-calcination. The temperature was increased to 850℃ at a heating rate of 5-10℃ / min and held for 2 hours to obtain pre-sintered powder.

[0081] Step 2: Cool the pre-sintered powder and place it together with 0.2 wt% MnO2 in a polytetrafluoroethylene ball mill jar for a second ball milling. The ball milling parameters are the same as the first ball milling. Take out the ball milled material and dry it. The drying parameters are the same as the first time. Add 8 wt% PVA aqueous solution as a binder. The mass of PVA aqueous solution is 10% of the total mass. At the same time, add 0.2 mL / g ethanol and mix it evenly in a mortar. After passing it through an 80-mesh sieve, press the resulting powder into a green embryo with a diameter of 13 mm under a pressure of 100 MPa for 2 min.

[0082] Step 3: Place the green blank in an alumina crucible and put it into a muffle furnace. Increase the temperature to 600℃ at 2℃ / min and hold for 2 hours to remove PVA. Then continue to heat the green blank at a rate of 5-10℃ / min and sinter at 1100℃ for 2 hours to obtain bismuth calcium titanate-based ferroelectric ceramic material.

[0083] Step 4: The sintered bismuth calcium titanate-based ferroelectric ceramic material is polished on both sides to a thickness of 0.5 mm, ultrasonically cleaned with ethanol, dried, and then silver electrodes are screen-printed. The electrodes are then sintered at 900℃ for 20 minutes to obtain the finished ferroelectric ceramic product. The ferroelectric properties of the bismuth calcium titanate-based ferroelectric ceramic material obtained in this example are as follows: Ps = 12.3 μC / cm². 2 Pr = 2.3 μC / cm 2 .

[0084] Comparative Example 1

[0085] The difference from Example 1 is that the doping amount of yttrium nitrate hexahydrate Y(NO3)3·6H2O in Example 1 is replaced by 6.0 mmol instead of 1.8 mmol, and the bismuth oxide content is replaced by 37.0 mmol instead of 39.1 mmol. The chemical formula is CaBi. 4- x Y x Ti4O 15 -yMnO2, where x = 0.3, y = 0.2 wt%, and other steps and parameters are the same as in Example 1.

[0086] Comparative Example 2

[0087] The difference from Example 2 is that the ethanol content in the granulation and tableting process of Example 2 is replaced by 0.05 mL / g instead of 0.2 mL / g. All other steps and parameters are the same as in Example 2.

[0088] Comparative Example 3

[0089] The difference from Example 2 is that yttrium nitrate hexahydrate Y(NO3)3·6H2O and manganese dioxide were not added in Comparative Example 1, and the bismuth oxide content was replaced from 39.1 mmol to 40 mmol. All other steps and parameters were the same as in Example 1.

[0090] Comparative Example 4

[0091] The difference from Example 2 is that no manganese dioxide was added in Comparative Example 4, while the other steps and parameters are the same as in Example 2.

[0092] The ferroelectric ceramics prepared in Examples 1-5 and Comparative Examples 1-4 were used as samples for performance testing. The relative density of the ceramics was calculated based on the bulk density determined according to GB / T 25995-2010 and X-ray diffraction data. The polarization intensity was tested using a Polyk PK-DIS2020 ferroelectric analyzer, and the testing standard was GB / T 6426-1999. The test results are shown in Table 1 below.

[0093] Table 1. Performance test results of bismuth titanate-calcium ferroelectric ceramic materials prepared in Examples 1-5 and Comparative Examples 1-4.

[0094]

Claims

1. A bismuth calcium titanate-based ferroelectric ceramic material, characterized in that, The chemical formula of the calcium bismuth titanate-based ferroelectric ceramic material is CaBi. 4-x R x Ti4O 15 -yMnO2, where R is one or more of the lanthanide rare earth elements, and 0 < x ≤ 0.2, 0.1 wt% ≤ y ≤ 0.5 wt%.

2. The bismuth calcium titanate-based ferroelectric ceramic material as described in claim 1, characterized in that, R is one or more of Sm, Y, Eu, Nd, Ce or La; The bismuth calcium titanate-based ferroelectric ceramic material uses layered bismuth calcium titanate as a matrix and is doped with rare earth elements and MnO2; wherein rare earth elements are doped at the A site in the layered bismuth calcium titanate, and Mn ions are doped at the B site in the layered bismuth calcium titanate.

3. A method for preparing a bismuth calcium titanate-based ferroelectric ceramic material as described in any one of claims 1-2, characterized in that, Includes the following steps: (1) Ingredients: Weigh and mix calcium carbonate, bismuth oxide, titanium oxide and rare earth element source to obtain mixed powder; (2) First ball milling: The mixed powder from step (1) is ball milled once; (3) Drying and pre-firing: The mixed slurry after ball milling in step (2) is dried and ground, and then compacted and pre-firing. The pre-firing is heated to 600-850 ℃ at a heating rate of 5-10 ℃ / min and kept at this temperature for 0.5-4h. (4) Secondary ball milling: Cool the powder after pre-calcination in step (3), add manganese oxide and perform secondary ball milling; (5) Drying and granulation: The mixed slurry after the second ball milling in step (4) is dried and ground. The obtained powder is granulated by adding PVA solution and 0.1-0.4 mL / g anhydrous ethanol and then sieved. (6) Pressing and sintering: Press the sieved powder in step (5) into a ceramic green body, remove the binder from the green body and sinter it to obtain a bismuth calcium titanate-based ferroelectric ceramic material.

4. The preparation method according to claim 3, characterized in that, The rare earth element source mentioned in step (1) is one or more of the oxides or nitrates of lanthanide rare earth elements; the content ratio of calcium carbonate, bismuth oxide, titanium oxide and rare earth element source is based on the chemical formula CaBi 4-x R x Ti4O 15 -yMnO2, 0<x≤0.2 are used for design; In steps (2) and (4), the first and second ball milling uses zirconia balls as the ball milling medium and anhydrous ethanol is added. The volume ratio of zirconia balls to raw materials is 1-2:1, and the volume ratio of zirconia balls to ethanol is 1:1-2. The ball milling time is 2-12 hours and the rotation speed is 200-500 rpm.

5. The preparation method according to claim 3, characterized in that, The drying and grinding described in steps (3) and (5) involves pouring the mixed slurry into a petri dish and drying it in a constant temperature oven for 6-24 hours to remove anhydrous ethanol. The resulting powder is then ground into powder in a mortar. The compaction and pre-firing described in step (3) involves compaction and sealing in an alumina crucible and pre-firing in a muffle furnace.

6. The preparation method according to claim 3, characterized in that, In step (4), manganese oxide is added for secondary ball milling, and the mass of the added manganese oxide is 0.1-0.5 wt% of the mass of the pre-calcined powder.

7. The preparation method according to claim 3, characterized in that, The granulation in step (5) specifically includes: weighing the dried and ground powder, adding a 5-8 wt% PVA solution at a ratio of 0.05-0.20 mL per gram of powder, and adding 0.1-0.4 mL / g of anhydrous ethanol, and mixing them evenly in a mortar; the sieving is performed using an 80-mesh sieve.

8. The preparation method according to claim 3, characterized in that, The pressing in step (6) specifically includes: taking the sieved powder from step (5) and holding it under a pressure of 50-200 MPa for 1-5 minutes, pressing it into a ceramic green body with a thickness of 10-14 mm; The debinding process specifically includes: placing the ceramic green body in an alumina crucible and then into a muffle furnace, filling and sealing it with the sieved powder from step (5), raising the temperature at a rate of 1-2℃ / min, raising it to 500-700℃ and holding it for 1-4 hours to remove the organic binder.

9. The preparation method according to claim 3, characterized in that, The sintering process in step (6) specifically includes: after removing the binder, continuing to raise the temperature at a rate of 5-10℃ / min until the temperature reaches 900-1200℃, and holding the temperature for 1-2 hours to obtain bismuth calcium titanate-based ferroelectric ceramic material.

10. The application of a bismuth calcium titanate-based ferroelectric ceramic material as described in any one of claims 1-2 or a bismuth calcium titanate-based ferroelectric ceramic material prepared by the preparation method as described in any one of claims 3-9, characterized in that, The bismuth titanate calcium-based ferroelectric ceramic material is polished to a thickness of 0.4-0.7 mm, ultrasonically cleaned with ethanol, dried, screen-printed with silver electrodes, and then fired to obtain the finished ferroelectric ceramic product.

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