阅读说明：本技术 一种高压电高居里点铌酸钾钠-锑酸钾钠系无铅压电陶瓷及其制备方法 (High-voltage high-Curie-point potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramic and preparation method thereof ) 是由 吴波 于 2020-03-31 设计创作，主要内容包括：本发明公开了一种高压电高居里点铌酸钾钠-锑酸钾钠系无铅压电陶瓷及其制备方法,该无铅压电陶瓷由通式0.965[(1-x)K<Sub>0.54</Sub>Na<Sub>0.476</Sub>NbO<Sub>3</Sub>-xK<Sub>0.54</Sub>Na<Sub>0.476</Sub>SbO<Sub>3</Sub>]–0.01Bi<Sub>2</Sub>O<Sub>3</Sub>-0.0025Fe<Sub>2</Sub>O<Sub>3</Sub>-0.03ZrO<Sub>2</Sub>表示,式中0.01≤x≤0.03。本发明采用两步法经传统陶瓷制备技术制取该高压电高居里点铌酸钾钠-锑酸钾钠系无铅压电陶瓷,其晶粒大小夹杂,微观结构致密,四方相含量高达70％以上,同时具有良好的压电性能、温度稳定性以及较高的居里温度,在压电传感器领域具有广泛的适用性,且可用于高温传感领域。(The invention discloses a high-voltage high-Curie point potassium-sodium niobate-potassium-sodium antimonate leadless piezoelectric ceramic and a preparation method thereof, wherein the leadless piezoelectric ceramic is prepared by a general formula of 0.965[ (1-x) K) 0.54 Na 0.476 NbO 3 ‑xK 0.54 Na 0.476 SbO 3 ]–0.01Bi 2 O 3 ‑0.0025Fe 2 O 3 ‑0.03ZrO 2 Expressed in the formula, x is more than or equal to 0.01 and less than or equal to 0.03. The invention adopts a two-step method to prepare the high-voltage high-Curie-point potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramic by the traditional ceramic preparation technology, the high-voltage high-Curie-point potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramic has the advantages of crystal grain size inclusion, compact microstructure, high tetragonal phase content of more than 70 percent, good piezoelectric property, temperature stability and higher Curie temperature, and has wide application in the field of piezoelectric sensorsApplicability and can be used in the field of high-temperature sensing.)

1. A high-voltage high-Curie point potassium sodium niobate-potassium sodium antimonate series leadless piezoelectric ceramic is characterized in that the general formula of the leadless piezoelectric ceramic is as follows:

0.965[(1-x)K_0.54Na_0.476NbO₃-xK_0.54Na_0.476SbO₃]-0.01Bi₂O₃-0.0025Fe₂O₃-0.03ZrO₂in the general formula, x is: x is more than or equal to 0.01 and less than or equal to 0.03.

2. The high-voltage high-curie-point potassium-sodium niobate-potassium-sodium antimonate lead-free piezoelectric ceramic according to claim 1, wherein x in the formula is 0.03.

3. The method for preparing the high-voltage high-curie-point potassium-sodium niobate-potassium-sodium antimonate lead-free piezoelectric ceramic of claim 1 or 2, characterized by comprising the steps of:

(1) compounding with K₂CO₃、Na₂CO₃、Nb₂O₅、Sb₂O₃As a raw material, according to the general formula K_0.54Na_0.476NbO₃And K_0.54Na_0.476SbO₃The molar ratios determined by the chemical formula are respectively weighed and proportioned;

(2) pre-sintering, namely respectively grinding and drying the raw materials prepared in the step (1), and then respectively pre-sintering at 800-900 ℃ for 4-6 h for K_0.54Na_0.476NbO₃And K_0.54Na_0.476SbO₃Synthesizing;

(3) compounding with K_0.54Na_0.476NbO₃、K_0.54Na_0.476SbO₃、Bi₂O₃、Fe₂O₃、ZrO₂Weighing and proportioning raw materials according to a chemical formula determined by a set value of x in the general formula of the lead-free piezoelectric ceramic;

(4) pre-sintering, namely grinding and drying the raw materials prepared in the step (3), and then pre-sintering at 750-900 ℃ for 4-8 h to synthesize a niobate compound to obtain pre-sintered powder;

(5) molding, namely adding a polyvinyl alcohol aqueous solution with the mass concentration of 5-7% into the obtained pre-sintered powder for granulation, and pressing and molding the obtained granules by using a mold;

(6) calcining, namely sintering the ceramic blank subjected to compression molding at 1060-1080 ℃ for 2-6 h to obtain sintered ceramic;

(7) and (3) polarizing, namely plating an electrode on the obtained sintered ceramic, putting the sintered ceramic into silicon oil, applying a direct current electric field of 2-3 kV/mm for polarization, and polarizing for 15-30 min to obtain the high-voltage high-Curie point potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramic.

4. The method for preparing high-voltage high-curie-point potassium-sodium niobate-sodium potassium antimonate leadless piezoelectric ceramics according to claim 3, wherein the prepared raw materials in the steps (2) and (4) are ground by using absolute ethyl alcohol as a ball milling medium.

5. The method for preparing high-voltage high-curie-point potassium-sodium niobate-sodium potassium antimonate leadless piezoelectric ceramics according to claim 4, characterized in that the prepared raw materials in steps (2) and (4) are ground by a rolling ball milling method by using absolute ethyl alcohol as a ball milling medium.

Technical Field

The invention belongs to the field of lead-free piezoelectric ceramics, relates to preparation of perovskite type alkali metal niobate-based lead-free piezoelectric ceramics, and particularly relates to high-voltage high-Curie point potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramics and a preparation method thereof.

Background

The piezoelectric ceramics have excellent performances of ferroelectricity, piezoelectricity, dielectricity and the like, and have wide application in the aspects of detection, conversion and storage of information such as electricity, magnetism, light, sound, heat, force and the like, and have been deeply applied to various fields of national safety and national economy. However, most of the piezoelectric ceramics in the market at present are lead-based piezoelectric ceramics, lead oxide in the production raw materials is toxic, the content of the lead oxide is more than 60%, and lead is a heavy metal element and has extremely high toxicity, so that serious harm is brought to the environment and human health in large-scale production, use and waste processes. With the improvement of human consciousness on ecological environment protection and the requirement of social sustainable development strategy, many countries have issued relevant laws to limit the use of lead in electronic and electric products. Therefore, research and development of lead-free piezoelectric ceramics which are environment-friendly have become an urgent and significant research task.

Currently, in the research of lead-free piezoelectric ceramics, three types of lead-free piezoelectric ceramics having perovskite structures, i.e., barium titanate (BaTiO), have been developed₃: BT) series, sodium bismuth titanate (Bi)_0.5Na_0.5TiO₃: BNT) series and alkali metal niobate (K)_0.5Na_0.5NbO₃: KNN) system, which is widely studied because of its superior performance and the prospect of being fabricated using conventional fabrication processes that enable mass production. Among them, perovskite-type alkali metal niobate-based lead-free piezoelectric ceramics are attracting much attention due to their relatively high piezoelectric performance and curie temperature, and are considered to be one of lead-free piezoelectric ceramic systems that are most promising as a substitute for lead-based piezoelectric ceramics. The phase boundary construction mode is reported to be a more effective means for improving the piezoelectric performance of the KNN series ceramic, namely reducing the orthorhombic-tetragonal phase transition temperature T_O-TConstructing an orthogonal-tetragonal phase boundary around room temperature; increasing the trigonal-orthorhombic phase transition temperature T_R-OConstructing a three-way-orthogonal phase boundary in a room temperature area; simultaneously reducing the orthorhombic-tetragonal phase transition temperature T_O-TAnd increasing the trigonal-orthorhombic phase transition temperature T_R-OAnd building a trigonal-orthogonal-tetragonal or trigonal-tetragonal phase boundary near room temperature. The piezoelectric coefficient of the KNN ceramic prepared by the idea is improved to a certain extent, and particularly the piezoelectric coefficient can be greatly improved when a trigonal-orthogonal-tetragonal or trigonal-tetragonal phase boundary is constructed near room temperature. The KNN-based ceramics obtained in this way haveThe piezoelectric constant is high, but the increase of the piezoelectric constant is accompanied with the decrease of the Curie temperature, so that the application temperature zone is narrowed, and the application range is limited. Therefore, it becomes important how to obtain a KNN-based ceramic system having both high piezoelectric properties and high curie temperature.

Disclosure of Invention

Aiming at the technical problem that the conventional KNN series ceramic system is difficult to have high piezoelectric property and high Curie point temperature at the same time, the invention aims to provide the high-voltage high-Curie point potassium sodium niobate-potassium sodium antimonate series lead-free piezoelectric ceramic and the preparation method thereof.

The above object of the present invention can be achieved by a high-voltage high curie point potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramic having the following general formula:

0.965[(1-x)K_0.54Na_0.476NbO₃-xK_0.54Na_0.476SbO₃]-0.01Bi₂O₃-0.0025Fe₂O₃-0.03ZrO₂x in the general formula is: x is more than or equal to 0.01 and less than or equal to 0.03; preferably, x is 0.03.

The preparation method of the high-voltage high-Curie point potassium-sodium niobate-potassium-sodium antimonate lead-free piezoelectric ceramic provided by the invention adopts a two-step method to prepare the lead-free piezoelectric ceramic, namely, K is synthesized firstly_0.54Na_0.476NbO₃And K_0.54Na_0.476SbO₃Compound according to the general formula 0.965[ (1-x) K_0.54Na_0.476NbO₃-xK_0.54Na_0.476SbO₃]-0.01Bi₂O₃-0.0025Fe₂O₃-0.03ZrO₂Weighing and proportioning the materials according to a chemical formula determined by the set value of the medium x, and introducing Bi₂O₃、Fe₂O₃、Zr O₂The method specifically comprises the following steps:

(1) compounding with K₂CO₃、Na₂CO₃、Nb₂O₅、Sb₂O₃Is used as a raw material for preparing the high-purity,according to the general formula K_0.54Na_0.476NbO₃And K_0.54Na_0.476SbO₃The chemical formulas are respectively weighed and proportioned;

(2) pre-sintering, namely respectively grinding and drying the raw materials prepared in the step (1), and then respectively pre-sintering at 800-900 ℃ for 4-6 h for K_0.54Na_0.476NbO₃And K_0.54Na_0.476SbO₃Synthesizing;

(3) compounding with K_0.54Na_0.476NbO₃、K_0.54Na_0.476SbO₃、Bi₂O₃、Fe₂O₃、ZrO₂Weighing and proportioning raw materials according to a chemical formula determined by a set value of x in the general formula of the lead-free piezoelectric ceramic;

(4) pre-sintering, namely grinding and drying the raw materials prepared in the step (3), and then pre-sintering at 750-900 ℃ for 4-8 h to synthesize a niobate compound to obtain pre-sintered powder;

(5) molding, namely adding a polyvinyl alcohol aqueous solution with the mass concentration of 5-7% into the obtained pre-sintered powder for granulation, and pressing and molding the obtained granules by using a mold;

(6) calcining, namely sintering the ceramic blank subjected to compression molding at 1060-1080 ℃ for 2-6 h to obtain sintered ceramic;

(7) and (3) polarizing, namely plating an electrode on the obtained sintered ceramic, putting the sintered ceramic into silicon oil, applying a direct current electric field of 2-3 kV/mm for polarization, and polarizing for 15-30 min to obtain the high-voltage high-Curie point potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramic.

In the preparation method of the high-voltage high-curie-point potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramic, the raw materials prepared in the steps (2) and (4) are preferably ground by using absolute ethyl alcohol as a ball milling medium, and are further preferably ground by using a rolling ball milling method.

The inventor finds that K is added to perovskite KNN-based lead-free piezoelectric ceramics in the research of the piezoelectric ceramics_0.54Na_0.476SbO₃Can simultaneously reduce the orthorhombic-tetragonal phase transition temperature and increase the orthorhombic-orthorhombic phase transition temperature to be near the room temperature, but the Curie temperature of the systemThe temperature also follows K_0.54Na_0.476SbO₃The content is increased and greatly reduced. The inventor also found that Bi is added in the research₂O₃、Fe₂O₃、ZrO₂Its effect on the orthorhombic-tetragonal and orthorhombic transformation temperatures of the system and K_0.54Na_0.476SbO₃Similarly, but with less Curie temperature reduction for the system. The inventors have found that K can be adjusted by adjusting K_0.54Na_0.476SbO₃And Bi₂O₃、Fe₂O₃、ZrO₂The addition amount of the compound is increased, on one hand, the construction and optimization of a three-square phase boundary of a KNN system are realized, and the piezoelectric performance of the compound is improved; on the other hand, by introducing Bi₂O₃、Fe₂O₃、ZrO₂Reducing K when building a trigonal-tetragonal phase boundary_0.54Na_0.476SbO₃The content is controlled to keep higher Curie temperature, and the technical scheme of the invention is completed through repeated experiments.

Compared with the prior art, the high-voltage high-Curie point potassium-sodium niobate-potassium-sodium antimonate lead-free piezoelectric ceramic and the preparation method thereof provided by the invention have the following beneficial effects:

1. the potassium-sodium niobate-potassium-sodium antimonate lead-free piezoelectric ceramic provided by the invention has small and compact crystal grain size inclusion and compact microstructure, and K is introduced at the same time_0.54Na_0.476SbO₃And Bi₂O₃、Fe₂O₃、ZrO₂The construction and optimization of the trigonal-tetragonal phase boundary of the KNN system are realized, and the lead-free piezoelectric ceramic has good piezoelectric property, temperature stability, higher Curie temperature and piezoelectric constant d₃₃The maximum temperature can reach about 505pC/N, and the Curie temperature T_CThe temperature is kept above 285 ℃, the temperature application range of the ceramic is widened, the piezoelectric sensor has wide applicability in the field of piezoelectric sensors, and the piezoelectric sensor can be used in the field of high-temperature sensing.

2. The potassium-sodium niobate-potassium-sodium antimonate lead-free piezoelectric ceramic prepared by the invention benefits from Bi₂O₃、Fe₂O₃、ZrO₂The crystal grains are mixed, the microstructure is compact, and the electrical property is favorably improved; especially by Fe₂O₃The introduction of (2) can reduce the sintering temperature on one hand, and has great influence on the microstructure on the other hand, such as grains with large and small impurities, and improves the structural density;

3. the potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramic provided by the invention can be obtained by adopting industrial raw materials through the traditional ceramic preparation technology, has a low sintering temperature (1060-1080 ℃), and is easy to realize;

4. the preparation method of the potassium-sodium niobate-potassium-sodium antimonate lead-free piezoelectric ceramic provided by the invention has the advantages of mature process and simple flow, and is beneficial to industrial scale production.

Drawings

FIG. 1 is an X-ray diffraction pattern of the potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramics prepared in examples 1 to 4.

FIG. 2 shows the X-ray diffraction refinement pattern (a) and the phase content (b) of the sodium potassium niobate-sodium potassium antimonate lead-free piezoelectric ceramic prepared in example 4.

FIG. 3 is a scanning electron micrograph of the potassium sodium niobate-potassium sodium antimonate-based lead-free piezoelectric ceramic prepared in example 4.

FIG. 4 shows the electrical properties of the potassium sodium niobate-potassium sodium antimonate-based lead-free piezoelectric ceramics prepared in examples 1 to 4.

FIG. 5 shows the dielectric temperature diagram (a) and the phase diagram (b) of the potassium sodium niobate-potassium sodium antimonate lead-free piezoelectric ceramic prepared in examples 1 to 4.

FIG. 6 is a graph showing the change in piezoelectric properties with annealing temperature of the potassium sodium niobate-potassium sodium antimonate-based lead-free piezoelectric ceramic prepared in example 4.

FIG. 7 is a graph showing the uniaxial strain with temperature of the potassium sodium niobate-potassium sodium antimonate-based lead-free piezoelectric ceramic prepared in example 4.

The general formula of the lead-free piezoelectric ceramic is a general structure of potassium sodium niobate-potassium sodium antimonate series lead-free piezoelectric ceramic designed according to the raw material proportion.

Detailed Description

The technical solutions of the present invention will be described in detail and fully with reference to the accompanying drawings, which are used for describing the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.