Background
The piezoelectric ceramic is a novel functional material capable of realizing the interconversion between mechanical energy and electric energy, is widely applied to various devices such as sensors, drivers, transducers and the like, and relates to the fields of machinery, communication, precise control, electronics, medical treatment and the like. With the rapid development of modern society, the research methods and test characterization means of materials are greatly improved, and the research on the microstructure and macroscopic electrical properties of piezoelectric ceramics is deepened, so that the piezoelectric ceramics are greatly developed, and the development and application value of novel functional devices based on piezoelectric materials in the high-tech field are further promoted.
The present lead-based piezoelectric ceramic is made of lead zirconate titanate (Pb (Zr, Ti) O3PZT), lead magnesium niobate (Pb (Mg)1/3Nb2/3)O3PMN) and the like, and are widely used due to their excellent electrostrictive propertiesGeneral application (F.Li, L.jin, Z.Xu, S.Zhang, Electrostrictive effect in semiconductors: an apple to an innovative piezoelectric conductivity, appl.Phys.Rev.2014,1: 011103/1-21). However, lead is a toxic element, and in the preparation process of lead-based ceramics, the volatilization of lead causes serious pollution to the environment and can harm human health, and the research of lead-free piezoelectric materials in various countries in the world is very important. For example, the european union came out in 2003 through the RoHS act, japan through the "home electronics recycling act", and china also in 2006 through the "electronic information product production pollution control management method". Therefore, the development of environment-friendly lead-free piezoelectric materials to replace lead-based materials is a great concern for the strategy of sustainable development.
Sodium bismuth titanate ((Bi)
0.5Na
0.5)TiO
3BNT) is a relaxor ferroelectric with perovskite structure compounded at A site, and BNT ceramic has high Curie temperature (T)
c320 c) and ferroelectric properties (P)
r=38μC/cm
2) And has been widely studied by various national scholars. However, pure BNT ceramics have large coercive field at room temperature, high leakage current and difficult polarization, and the piezoelectric properties thereof cannot meet the requirements of practical applications. In order to improve the performance of ceramics, researchers in various countries have conducted intensive studies on various aspects such as system construction, microstructure, phase transition characteristics, and preparation process (d.q.xiao, j.g.wu, l.wu, j.g.zhu, p.yu, d.m.lin, y.w.liao, y.sun, investment on the composition design and properties test of property lead-ee piezoelectric ceramics, j.mater.sci.2009,44: 5408-. In recent years, researchers have found that by introducing a second or third element into a BNT-based ceramic to form a binary or ternary system, the ferroelectric-relaxor phase transition temperature can be controlled to be around room temperature, thereby inducing high electrostrictive strain in the BNT-based ceramic, and the strain value can be comparable to that of lead-based PZT ceramic, thus showing important application value (w.jo, r.dittm, m.acosta, j.zang, c.groh, e.sapper, k.wang, J).

Giant electric-field-induced strains in lead-free ceramics for actuator applications-status andPerproductive, J.Electroceram.2012,29: 71-93). However, there are only few reports in the literature on Bi element non-stoichiometric BNT based ceramics with high electrostrictive strain.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a non-stoichiometric sodium bismuth titanate-based ceramic with larger reversible strain response.
Another object of the present invention is to provide a method for preparing a non-stoichiometric sodium bismuth titanate-based ceramic.
Another object of the present invention is to provide the use of non-stoichiometric bismuth sodium titanate-based ceramics.
The purpose of the invention can be realized by the following technical scheme:
the bismuth sodium titanate-based ceramic with non-stoichiometric ratio has the raw material composition of 0.99Bi0.5+x(Na0.8K0.2)0.5TiO3-0.01SrTiO3Wherein x is 0 to 0.025, and preferably 0.025.
The preparation method of the non-stoichiometric bismuth titanate sodium-based ceramic comprises the following steps:
(1) selecting Bi with the purity of more than 99 percent2O3、Na2CO3、K2CO3、TiO2And SrCO3As a raw material for sodium bismuth titanate-based ceramics;
(2) according to 0.99Bi0.5+x(Na0.8K0.2)0.5TiO3-0.01SrTiO3Weighing raw materials according to the formula, and drying the raw materials after ball milling;
(3) pre-burning the dried raw materials at 800-900 ℃ for 3-6 h;
(4) performing secondary ball milling, drying and granulation on the pre-sintered powder, pressing the powder under the pressure of 50-100MPa to prepare a ceramic blank, performing gel removal at the temperature of 500-600 ℃, and preserving the heat for 8-12 h;
(5) sintering the green body after the glue is removed at 1140-1160 ℃ for 2-4 h; and naturally cooling to room temperature, thinning and polishing the sintered porcelain sample to obtain the non-stoichiometric bismuth sodium titanate-based ceramic.
And (3) adopting absolute ethyl alcohol and zirconia balls as ball milling media in the ball milling in the steps (2) and (4), wherein the mass ratio of the zirconia balls to the raw materials is 1.2: 1-1.5: 1, the mass ratio of the absolute ethyl alcohol to the raw materials is 1.5: 1-2.5: 1, the ball milling speed is controlled at 200-400r/min, and the ball milling time is 10-15 h.
And (4) adding 8 wt% of PVA into the powder in the step (4) before granulation, pressing to obtain a ceramic blank with the diameter of 10mm and the thickness of 0.8-1 mm, and controlling the heating rate at 1 ℃/min during rubber discharge.
The sintering temperature adopted in the step (5) is preferably 1150 ℃, and the temperature rise speed is controlled to be 3 ℃/min during sintering.
The non-stoichiometric sodium bismuth titanate-based ceramic is applied to piezoelectric sensors, drivers and high-precision displacement controllers.
Compared with the prior art, the production process is simple and repeatable, a nonpolar phase can be induced at a critical component with 0.025mol excess Bi by regulating the stoichiometric ratio of Bi elements, the nonpolar phase and a ferroelectric phase can be mutually transformed under the action of an electric field, and the reversible phase change generates high electrostrictive property. When the Bi exceeds 0.025mol, the content of the nonpolar phase is increased, a higher excitation electric field is required for inducing the ferroelectric phase, and the electrostriction value is reduced. The bismuth sodium titanate-based ceramic has better electrostrictive strain performance than a lead-based piezoelectric material at room temperature by regulating the Bi content, and the bismuth sodium titanate-based ceramic still has excellent strain performance at high temperature, can be applied to piezoelectric sensors, drivers and high-precision displacement controllers, and has important significance for replacing lead-based electrostrictive materials.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
Example 1
(1) According to 0.99Bi0.50+x(Na0.8K0.2)0.5TiO3-0.01SrTiO3Weighing raw materials according to the formula of Bi, Na, K, Ti and Sr in the x-0, mixing, carrying out primary ball milling for 12 hours to obtain raw material powder, drying, presintering at 850 ℃ for 4 hours to obtain presynthesized powder, and carrying out secondary ball milling for 12 hours on the presynthesized powder. Drying the abrasive, adding 8 wt% of PVA (polyvinyl alcohol) for granulation, then carrying out compression molding at 50-100MPa to obtain a wafer with the diameter of 10mm and the thickness of 0.8-1.0 mm, and carrying out degumming at 550 ℃ and sintering at 1150 ℃ for 3h to obtain the required ceramic material.
And thinning and polishing the sintered ceramic wafer to obtain a sheet with the thickness of 0.5mm, coating silver electrodes on the upper surface and the lower surface of the wafer, and testing the electrostrictive property.
Example 2
(1) According to 0.99Bi0.50+x(Na0.8K0.2)0.5TiO3-0.01SrTiO3Weighing raw materials according to a formula of Bi, Na, K, Ti and Sr in the x-0.01, mixing, performing primary ball milling for 12 hours to obtain raw material powder, drying, pre-sintering at 850 ℃ for 4 hours to obtain pre-synthesized powder, and performing secondary ball milling for 12 hours to obtain composite powder. Drying the composite powder, adding 8 wt% of PVA (polyvinyl alcohol) for granulation, then carrying out compression molding at 50-100MPa to obtain a wafer with the diameter of 10mm and the thickness of 0.8-1.0 mm, discharging glue at 550 ℃, and sintering at 1150 ℃ for 3 hours to obtain a ceramic sample.
And thinning and polishing the ceramic sample to obtain a sheet with the thickness of 0.5mm, coating silver electrodes on the upper surface and the lower surface of the sheet, and testing the electrostrictive strain performance.
Example 3
(1) According to 0.99Bi0.50+x(Na0.8K0.2)0.5TiO3-0.01SrTiO3And weighing raw materials according to the formula of Bi, Na, K, Ti and Sr in 0.02, mixing, and performing primary ball milling for 12 hours to obtain raw material powder. Presintering the dried powder for 4h at 850 ℃ to obtain presynthesized powder, and performing secondary ball milling on the presynthesized powder for 12 h. And (3) drying the abrasive, adding 8 wt% of PVA (polyvinyl alcohol) for granulation, then carrying out compression molding at 50-100MPa to obtain a wafer with the diameter of 10mm and the thickness of 0.8-1.0 mm, and carrying out degumming at 550 ℃ and sintering at 1150 ℃ for 3 hours to obtain a ceramic sample.
And thinning the sintered ceramic wafer to 0.5mm, polishing to obtain a bright surface, coating silver electrodes on the upper surface and the lower surface of the wafer, and testing the electrostrictive property.
Example 4
(1) According to 0.99Bi0.50+x(Na0.8K0.2)0.5TiO3-0.01SrTiO3Weighing raw materials according to a formula of Bi, Na, K, Ti and Sr in 0.025, mixing, carrying out primary ball milling for 12h to obtain raw material powder, drying, presintering at 850 ℃ for 4h to obtain presynthesized powder, and carrying out secondary ball milling for 12h to obtain composite powder. Drying the composite powder, adding 8 wt% of PVA (polyvinyl alcohol) for granulation, then carrying out compression molding at 50-100MPa to obtain a wafer with the diameter of 10mm and the thickness of 0.8-1.0 mm, discharging glue at 550 ℃, and sintering at 1150 ℃ for 3 hours to obtain a ceramic sample.
And thinning and polishing the ceramic sample to obtain a sheet with the thickness of 0.5mm, coating silver electrodes on the upper surface and the lower surface of the sheet, and testing the electrostrictive strain performance.
FIG. 1 is an XRD spectrum of non-stoichiometric sodium bismuth titanate-based ceramics prepared by the invention in examples 1-4, the prepared ceramics have a pure perovskite phase structure, no second phase is generated, and the components in examples 1-4 are all pseudo cubic phase structures.
FIG. 2 shows the hysteresis loops of the non-stoichiometric sodium bismuth titanate-based ceramics prepared according to the present invention in examples 1-4, and the hysteresis loops of the ceramics prepared in examples 1-3 are saturated and have normal ferroelectric characteristics. The ferroelectric hysteresis loop of the ceramic prepared in example 4 is in a beam waist shape and exhibits a non-polar phase characteristic.
FIG. 3 is an electrostrictive strain curve of the non-stoichiometric sodium bismuth titanate-based ceramics prepared in accordance with the present invention for examples 1-4, with a test electric field of 6kV/mm, 0.17% strain for the ceramics prepared in example 1, 0.19% strain for the ceramics prepared in example 2, 0.24% strain for the ceramics prepared in example 3, and up to 0.33% strain for the ceramics prepared in example 4, corresponding to a dynamic piezoelectric coefficient Smax/EmaxThe lead-free bismuth titanate lead-free ceramic has the maximum advantage that the lead-free bismuth titanate lead-free ceramic can achieve high electrical strain performance by regulating and controlling the stoichiometric ratio of Bi element, and is comparable to lead-based PZT ceramic.
Fig. 4 shows that the change of the electrostrictive strain value of the non-stoichiometric sodium bismuth titanate-based ceramic prepared in example 4 of the invention with temperature is small in the range of 20-120 ℃, and the electrostrictive strain can still reach 0.28% at a high temperature of 120 ℃, which indicates that the material has good temperature stability and can meet the requirements of practical application.
Example 5
The bismuth sodium titanate-based ceramic with non-stoichiometric ratio has the raw material composition of 0.99Bi0.5(Na0.8K0.2)0.5TiO3-0.01SrTiO3The preparation method of the non-stoichiometric bismuth sodium titanate-based ceramic comprises the following steps:
(1) selecting Bi with the purity of more than 99 percent2O3、Na2CO3、K2CO3、TiO2And SrCO3As a raw material for sodium bismuth titanate-based ceramics;
(2) according to 0.99Bi0.5(Na0.8K0.2)0.5TiO3-0.01SrTiO3Weighing raw materials, performing ball milling, and drying, wherein absolute ethyl alcohol and zirconia balls are used as ball milling media during ball milling, the mass ratio of the zirconia balls to the raw materials is 1.2:1, the mass ratio of the absolute ethyl alcohol to the raw materials is 1.5:1, the ball milling speed is controlled at 200r/min, and the ball milling time is 15 hours;
(3) pre-burning the dried raw materials at 800 ℃ for 6 h;
(4) performing secondary ball milling on the pre-sintered powder, wherein absolute ethyl alcohol and zirconia balls are used as ball milling media during ball milling, the mass ratio of the zirconia balls to the raw materials is 1.2:1, the mass ratio of the absolute ethyl alcohol to the raw materials is 1.5:1, the ball milling rotating speed is controlled at 200r/min, the ball milling time is 15 hours, then drying and granulating are performed, 8 wt% of PVA is added before granulation, the mixture is pressed into a ceramic blank with the diameter of 10mm and the thickness of 0.8mm under the pressure of 50MPa, glue discharging is performed at 500 ℃, the heating rate is controlled at 1 ℃/min during glue discharging, and the heat preservation is performed for 12 hours;
(5) and sintering the blank after the glue is removed at 1140 ℃ for 4h, controlling the heating rate to be 3 ℃/min during sintering, naturally cooling to room temperature, and thinning and polishing a sintered ceramic sample to obtain the non-stoichiometric bismuth sodium titanate-based ceramic. The method can be applied to piezoelectric sensors, drivers and high-precision displacement controllers.
Example 6
The bismuth sodium titanate-based ceramic with non-stoichiometric ratio has the raw material composition of 0.99Bi0.51(Na0.8K0.2)0.5TiO3-0.01SrTiO3The preparation method of the non-stoichiometric bismuth sodium titanate-based ceramic comprises the following steps:
(1) selecting Bi with the purity of more than 99 percent2O3、Na2CO3、K2CO3、TiO2And SrCO3As a raw material for sodium bismuth titanate-based ceramics;
(2) according to 0.99Bi0.51(Na0.8K0.2)0.5TiO3-0.01SrTiO3Weighing raw materials, performing ball milling, and drying, wherein absolute ethyl alcohol and zirconia balls are used as ball milling media during ball milling, the mass ratio of the zirconia balls to the raw materials is 1.3:1, the mass ratio of the absolute ethyl alcohol to the raw materials is 1.6:1, the ball milling speed is controlled at 300r/min, and the ball milling time is 18 hours;
(3) pre-burning the dried raw materials at 850 ℃ for 4 h;
(4) performing secondary ball milling on the pre-sintered powder, wherein absolute ethyl alcohol and zirconia balls are used as ball milling media during ball milling, the mass ratio of the zirconia balls to the raw materials is 1.3:1, the mass ratio of the absolute ethyl alcohol to the raw materials is 1.6:1, the ball milling rotating speed is controlled at 300r/min, the ball milling time is 18h, then drying and granulating are performed, 8 wt% of PVA is added before granulation, the mixture is pressed into a ceramic blank with the diameter of 10mm and the thickness of 0.9mm under the pressure of 80MPa, glue discharging is performed at 550 ℃, the heating rate is controlled at 1 ℃/min during glue discharging, and the heat preservation is performed for 10 h;
(5) and sintering the blank after the glue is removed at 1150 ℃ for 3h, controlling the heating rate at 3 ℃/min during sintering, naturally cooling to room temperature, and thinning and polishing a sintered ceramic sample to obtain the non-stoichiometric bismuth sodium titanate-based ceramic. The ceramic can be applied to piezoelectric sensors, drivers and high-precision displacement controllers.
Example 7
The bismuth sodium titanate-based ceramic with non-stoichiometric ratio has the raw material composition of 0.99Bi0.525(Na0.8K0.2)0.5TiO3-0.01SrTiO3The preparation method of the non-stoichiometric bismuth sodium titanate-based ceramic comprises the following steps:
(1) selecting Bi with the purity of more than 99 percent2O3、Na2CO3、K2CO3、TiO2And SrCO3As a raw material for sodium bismuth titanate-based ceramics;
(2) according to 0.99Bi0.525(Na0.8K0.2)0.5TiO3-0.01SrTiO3Weighing raw materials, performing ball milling, and drying, wherein absolute ethyl alcohol and zirconia balls are used as ball milling media during ball milling, the mass ratio of the zirconia balls to the raw materials is 1.5:1, the mass ratio of the absolute ethyl alcohol to the raw materials is 2.5:1, the ball milling speed is controlled at 400r/min, and the ball milling time is 10 hours;
(3) pre-burning the dried raw materials at 900 ℃ for 3 h;
(4) performing secondary ball milling on the pre-sintered powder, wherein absolute ethyl alcohol and zirconia balls are used as ball milling media during ball milling, the mass ratio of the zirconia balls to the raw materials is 1.5:1, the mass ratio of the absolute ethyl alcohol to the raw materials is 2.5:1, the ball milling rotating speed is controlled at 400r/min, the ball milling time is 10 hours, then drying and granulating are performed, 8 wt% of PVA is added before granulation, the mixture is pressed into a ceramic blank with the diameter of 10mm and the thickness of 1mm under the pressure of 100MPa, glue discharging is performed at 600 ℃, the heating rate is controlled at 1 ℃/min during glue discharging, and the heat preservation is performed for 8 hours;
(5) and sintering the blank after the glue is removed at 1140 ℃ for 2h, controlling the heating rate to be 3 ℃/min during sintering, naturally cooling to room temperature, and thinning and polishing a sintered ceramic sample to obtain the non-stoichiometric bismuth sodium titanate-based ceramic. The ceramic can be applied to piezoelectric sensors, drivers and high-precision displacement controllers.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.