Leadless piezoelectric ceramic and preparation method thereof
Technical Field
The invention relates to the technical field of piezoelectric ceramics, in particular to a lead-free piezoelectric material and a preparation method thereof.
Background
The piezoelectric material has positive and negative piezoelectric properties and can realize the interconversion between mechanical energy and electric energy, so the piezoelectric material is widely applied to high and new technical fields such as piezoelectric resonators, piezoelectric buzzers, piezoelectric filters, piezoelectric transformers, piezoelectric speakers, piezoelectric igniters, piezoelectric motors and the like as an important functional material.
At present, lead-based piezoelectric ceramics are the most widely used piezoelectric materials, but the content of lead oxide in the raw materials of lead-based piezoelectric ceramics is usually as high as more than 60%. As is well known, lead is a toxic substance, and is accumulated in the human body and not easy to be discharged, thereby causing serious harm to the human health. Meanwhile, the environment is very easily polluted in the production and use processes. Therefore, the research on the lead-free piezoelectric ceramic with high performance is of great significance.
Alkali metal niobate (K)0.5Na0.5NbO3: KNN) has a high curie temperature and a large electromechanical coupling coefficient, which is considered to be the most promising lead-free piezoelectric ceramic material to replace lead-based piezoelectric ceramics. However, the sintering temperature of the material is high, and the alkali metal raw material is easily volatilized at high-temperature sintering, so that the compactness and the piezoelectric property of the ceramic are reduced. Meanwhile, the temperature stability is also an important factor for limiting the wide application of the KNN-based lead-free piezoelectric ceramic, so that the sintering temperature of the KNN-based lead-free piezoelectric ceramic is reduced, and the improvement of the temperature stability is of great importance for the lead-free piezoelectric ceramic.
Disclosure of Invention
The invention aims to provide a novel technical scheme of lead-free piezoelectric ceramics.
According to a first aspect of the present invention, there is provided a lead-free piezoelectric ceramic. The ceramic is represented by the following chemical formula I:
(KaNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)x-Gy(I)
wherein x is more than or equal to 0 and less than or equal to 0.10, y is more than or equal to 0 and less than or equal to 2.0, a is more than 0 and less than or equal to 0.8, b is more than 0 and less than or equal to 0.8, c is more than or equal to 0 and less than or equal to 0.08, d is more than or equal to 0 and less than or equal to 0.08, e is more than or equal to 0 and less than or equal to 0.06, f is more than or equal to 0 and less than or,
wherein G is selected from one or a mixture of more of rare earth element oxides, CuO and ZnO,
wherein y is a compound (K) occupied by GaNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)xMole percent of (c).
Optionally, wherein 0. ltoreq. x.ltoreq.0.04, 0. ltoreq. y.ltoreq.1.5, 0.32. ltoreq. a.ltoreq.0.60, 0.40. ltoreq. b.ltoreq.0.68, and 0.6. ltoreq. a/b.ltoreq.1.3, 0. ltoreq. c.ltoreq.0.02, 0. ltoreq. d.ltoreq.0.02, 0. ltoreq. e.ltoreq.0.04, 0. ltoreq. f.ltoreq.0.02, 0. ltoreq. g.ltoreq.0.02.
Optionally, the oxide of the rare earth element is CeO2。
Optionally, the lead-free piezoelectric ceramic is of a perovskite structure.
According to a second aspect of the present invention, there is provided a method for producing a lead-free piezoelectric ceramic. The preparation method comprises the following steps:
s1, batching:
with K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3、ZrO2And G is a raw material, each raw material being according to the chemical formula (K)aNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)x-GyThe set values of a, b, c, d, e, f, g, j, x and y in the step (a) and (b) are weighed and proportioned,
wherein x is more than or equal to 0 and less than or equal to 0.10, y is more than or equal to 0 and less than or equal to 2.0, a is more than 0 and less than or equal to 0.8, b is more than 0 and less than or equal to 0.8, c is more than or equal to 0 and less than or equal to 0.08, d is more than or equal to 0 and less than or equal to 0.08, e is more than or equal to 0 and less than or equal to 0.06, f is more than or equal to 0 and less than or,
wherein G is selected from one or a mixture of more of rare earth element oxides, CuO and ZnO,
wherein y is a compound (K) occupied by GaNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)xMole percent of (c);
s2 preparation
S21, mixing K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3And ZrO2Pre-burning the mixture to obtain a first pre-burning powder material,
s22, adding G into the first pre-sintering powder, preparing into mixed powder,
s23, adding granulating agent into the mixed powder to form powder with good fluidity, preparing the powder into rough blank with set shape,
s24, carrying out glue discharging treatment on the rough blank,
s25, sintering the rough blank subjected to the glue removing treatment to obtain a ceramic element;
s3 polarization
And polarizing the ceramic element to obtain the lead-free piezoelectric ceramic device.
Optionally, in step S21, the method includes:
to K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3And ZrO2Adding absolute ethyl alcohol into the mixture, and carrying out primary mixed grinding;
drying the mixture after the first mixing and grinding;
and pre-burning the dried mixture to obtain first pre-burning powder.
Optionally, the first mixing and grinding time is 10-30 hours, the pre-sintering temperature is 850-.
Optionally, in step S22, the method includes: adding absolute ethyl alcohol into the first pre-sintering powder added with the G, and carrying out second mixed grinding;
and drying the powder after the second mixing and grinding to obtain mixed powder.
Optionally, in the step S23, the granulating agent is an aqueous solution of polyvinyl alcohol, and the mass concentration of the aqueous solution of polyvinyl alcohol is 4% to 12%.
Optionally, in the step S25, the sintering temperature is 920-1120 ℃, and the sintering time is 2-6 hours.
Optionally, in step S3, the method includes: plating electrodes on the ceramic element, and putting the ceramic element into silicon oil to apply direct current of 2-4kV/mm to carry out polarization for 15-30 minutes.
According to a third aspect of the present invention, there is provided a method for producing a lead-free piezoelectric ceramic. The preparation method comprises the following steps:
SS1, ingredients:
with K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3、ZrO2And G is a raw material, each raw material being according to the chemical formula (K)aNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)x-GyThe set values of a, b, c, d, e, f, g, j, x and y in the step (a) and (b) are weighed and proportioned,
wherein x is more than or equal to 0 and less than or equal to 0.10, y is more than or equal to 0 and less than or equal to 2.0, a is more than 0 and less than or equal to 0.8, b is more than 0 and less than or equal to 0.8, c is more than or equal to 0 and less than or equal to 0.08, d is more than or equal to 0 and less than or equal to 0.08, e is more than or equal to 0 and less than or equal to 0.06, f is more than or equal to 0 and less than or,
wherein G is selected from one or a mixture of more of rare earth element oxides, CuO and ZnO,
wherein y is a compound (K) occupied by GaNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)xMole percent of (c);
SS2 preparation
SS21, K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3、ZrO2And G to obtain a second calcined powder,
SS22, adding granulating agent into the second pre-sintering powder to form powder with good fluidity, preparing the powder into rough blank with set shape,
SS23, carrying out glue discharging treatment on the rough blank,
SS24, sintering the rough blank after the glue discharging treatment to obtain a ceramic element;
SS3, polarization
And polarizing the ceramic element to obtain the lead-free piezoelectric ceramic device.
Optionally, in the step of SS21, the presintering temperature is 850-900 ℃, and the presintering time is 3-8 hours.
Optionally, in the step of SS22, the granulating agent is an aqueous solution of polyvinyl alcohol, and the mass concentration of the aqueous solution of polyvinyl alcohol is 4-12%.
Optionally, in the step of SS24, the sintering temperature is 920-1120 ℃, and the sintering time is 2-6 hours.
Optionally, in the step of SS3, the method comprises: plating electrodes on the ceramic element, and putting the ceramic element into silicon oil to apply direct current of 2-4kV/mm to carry out polarization for 15-30 minutes.
The inventors of the present invention have found that in the prior art, alkali metal niobate (K)0.5Na0.5NbO3: KNN) has a higher curie temperature and a larger electromechanical coupling coefficient. However, the sintering temperature of the material is high, and the alkali metal raw material is easily volatilized at high-temperature sintering, resulting in a decrease in the compactness and piezoelectric properties of the ceramic. Therefore, the technical task to be achieved or the technical problems to be solved by the present invention are never thought or anticipated by those skilled in the art, and therefore the present invention is a new technical solution.
Detailed Description
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
According to one embodiment of the present invention, a lead-free piezoelectric ceramic is provided. The lead-free piezoelectric ceramic is represented by the following chemical formula I:
(KaNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)x-Gy(I)
wherein x is more than or equal to 0 and less than or equal to 0.10, y is more than or equal to 0 and less than or equal to 2.0, a is more than 0 and less than or equal to 0.8, b is more than 0 and less than or equal to 0.8, c is more than or equal to 0 and less than or equal to 0.08, d is more than or equal to 0 and less than or equal to 0.08, e is more than or equal to 0 and less than or equal to 0.06, f is more than or equal to 0 and less than or,
wherein G is selected from one or a mixture of more of rare earth element oxides, CuO and ZnO. During preparation, G is added into the raw materials as a sintering aid, so that the sintering temperature of the lead-free piezoelectric ceramic is obviously reduced, and the volatilization of alkali metal raw materials is reduced.
Wherein y is a compound (K) occupied by GaNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)xMole percent of (c).
G may be one or a mixture of more of rare earth oxide, CuO, and ZnO. Preferably, the oxide of a rare earth element is cerium oxide (CeO)2)。CeO2The doped compound I has more excellent piezoelectric performance.
y is in the range of 0-2.0, i.e. G is in the compound (K)aNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1- jCajZrO3)xThe mole percentage of (B) is 0-2.0%.
The lead-free piezoelectric ceramic provided by the invention has the characteristics of high piezoelectric constant d33, small fluctuation range of reverse piezoelectric coefficient d33 ﹡ in the temperature range from room temperature to 170 ℃, and high Curie temperature Tc.
In addition, the lead-free piezoelectric ceramic has high compactness.
In addition, the lead-free piezoelectric ceramic has wide applicability.
Preferably, the ranges for the individual parameters in formula I are 0. ltoreq. x.ltoreq.0.04, 0. ltoreq. y.ltoreq.1.5, 0.32. ltoreq. a.ltoreq.0.60, 0.40. ltoreq. b.ltoreq.0.68, and 0.6. ltoreq. a/b.ltoreq.1.3, 0. ltoreq. c.ltoreq.0.02, 0. ltoreq. d.ltoreq.0.02, 0. ltoreq. e.ltoreq.0.04, 0. ltoreq. f.ltoreq.0.02, 0. ltoreq. g.ltoreq.0.02, 0.
Within the value range, the lead-free piezoelectric ceramic has more excellent comprehensive performance, higher piezoelectric constant d33 and better stability of reverse piezoelectric coefficient d33 ﹡ at different temperatures.
Preferably, the lead-free piezoelectric ceramic is of a perovskite structure. The ceramic material with the structure has good piezoelectric effect.
According to another embodiment of the present invention, there is provided a method for preparing a lead-free piezoelectric ceramic, including the steps of:
s1, preparing the ingredients
With K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3、ZrO2And G is a starting material, each starting material according to formula I (K)aNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)x-GyThe set values of a, b, c, d, e, f, g, j, x and y in the step (a) and (b) are weighed and proportioned,
wherein x is more than or equal to 0 and less than or equal to 0.10, y is more than or equal to 0 and less than or equal to 2.0, a is more than 0 and less than or equal to 0.8, b is more than 0 and less than or equal to 0.8, c is more than or equal to 0 and less than or equal to 0.08, d is more than or equal to 0 and less than or equal to 0.08, e is more than or equal to 0 and less than or equal to 0.06, f is more than or equal to 0 and less than or,
wherein G is selected from one or a mixture of more of rare earth element oxides, CuO and ZnO,
wherein y is a compound (K) occupied by GaNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)xMole percent of (c).
Specifically, the raw materials are powder materials. And weighing and proportioning according to the proportional relation of each element in the chemical formula I. G can be one or more of rare earth element oxide, CuO and ZnO.
The sintering temperature of the lead-free piezoelectric ceramic is reduced by adding the sintering aid G, so that the volatilization of alkali metal under high-temperature sintering is greatly reduced, and the compactness and the piezoelectric property of the lead-free piezoelectric ceramic are improved.
The amount of each raw material can be set by those skilled in the art according to actual needs.
S2 preparation
S21, mixing K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3And ZrO2The mixture of (a) is subjected to pre-firing to obtain a first pre-fired powder.
For example, in this step, first, K is added2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3And ZrO2The mixture of (1) is added with absolute ethyl alcohol and is subjected to first mixed grinding. The addition of anhydrous ethanol can increase the viscosity of the raw materialThereby leading the first mixing and grinding to be more sufficient and leading the obtained powder to be more fine and uniform. The first mixing and grinding is carried out by adopting a ball milling method. Preferably, the first milling time is 10 to 30 hours. Further, the time for the first mixed grinding was 20 hours. During the mixing and grinding process, the powder becomes finer and more uniform.
And then, drying the mixture after the first mixing and grinding to remove the absolute ethyl alcohol.
And finally, pre-burning the dried mixture to obtain first pre-burning powder. The purpose of the pre-burning is: the solid phase chemical reaction of each raw material is sufficient and uniform, solid solution with fixed composition is generated, and a main crystal phase is formed; and carbon dioxide and moisture in the raw materials are removed, and the sintering shrinkage and deformation of the rough blank are reduced, so that the appearance size of the ceramic product is controlled.
Preferably, the pre-firing temperature is 850-. The pre-sintering time is 3-8 hours. Under the pre-sintering condition, the solid-phase chemical reaction of each raw material is more sufficient and uniform. Further, the burn-in time was 5 hours.
S22, adding G into the first pre-sintering powder, and preparing into mixed powder.
For example, in this step, the following steps are included: and adding absolute ethyl alcohol into the first pre-sintering powder added with the G, and carrying out second mixed grinding. In the same way, the addition of the absolute ethyl alcohol can increase the viscosity of the first pre-sintered powder, so that the second mixing and grinding is more sufficient, and the obtained first pre-sintered powder is finer and more uniform.
And drying the powder after the second mixing and grinding to obtain mixed powder. The anhydrous ethanol can be removed through drying, and adverse effects of the anhydrous ethanol on subsequent sintering are avoided. For example, the second mixing and milling also employs a ball milling method. Preferably, the time for the second mixing and milling is 20 hours. And the mixed powder is subjected to secondary mixing and grinding to obtain finer and more uniform mixed powder.
S23, adding a granulating agent into the mixed powder to form powder with good fluidity, and preparing the granulated powder into a rough blank with a set shape. For example, the blank is formed by a die pressing method, and the size of the obtained rough blank is phi 10 x 2 mm. The shape of the rough blank is prepared according to the structure of the piezoelectric sheet.
Preferably, the granulating agent is an aqueous solution of polyvinyl alcohol. The mass concentration of the aqueous solution of the polyvinyl alcohol is 4-12%. The granulating agent has the characteristics of high viscosity and small dosage.
And S24, carrying out glue discharging treatment on the rough blank. The purpose of the binder removal is to remove high molecular compounds such as polyvinyl alcohol and the like from the rough blank so as to avoid adverse effects on sintering. The high molecular compound contains a large amount of carbon, and when oxygen is insufficient, carbon monoxide having a strong reducibility is produced by combustion. Carbon monoxide is capable of reducing the oxides in the feedstock to metals or suboxides. The metal or suboxide affects the color, ceramic forming, platability and polarization of the ceramic.
In one example, pre-dumping is first performed with an organic solvent. Optionally, the pre-arranged gel is prepared by one of trichloroethylene, carbon tetrachloride, chloroform and acetone as an organic solvent.
Then, the rough blank after pre-degumming is subjected to degumming treatment at high temperature so as to completely remove organic matters such as polyvinyl alcohol and the like. The temperature of the glue discharging treatment is 500-700 ℃.
In another example, the preform is directly subjected to a degumming treatment at elevated temperature, in which way also high molecular compounds such as polyvinyl alcohol can be excluded.
And S25, sintering the rough blank after the glue discharging treatment to obtain the ceramic element. Sintering may be carried out in an atmospheric sintering furnace. Preferably, the sintering temperature is 920-1120 ℃, and the sintering time is 2-6 hours. The green compact is sintered under these conditions to finally form a perovskite-structured ceramic element. The ceramic element is represented by compound I. Spontaneous polarization exists in all directions in the crystal of the ceramic element, and no polarity is presented to the outside from the macroscopic view. The regions where the spontaneous polarizations are in the same direction are called electric domains.
S3 polarization
And polarizing the ceramic element to obtain the lead-free piezoelectric ceramic device. The electric domain of the ceramic element is polarized to change direction, that is, the spontaneous polarization of the electric domain is forced by polarization to be oriented, so that the ceramic element presents polarity.
Preferably, in this step, the method comprises: first, electrodes are plated on the ceramic element to facilitate polarization.
Then, the ceramic element is put into silicone oil and a direct current of 2-4kV/mm is applied to perform polarization for 15-30 minutes.
By polarization, the ceramic element becomes a piezoelectric ceramic device having piezoelectric properties.
In other examples, the ceramic element is directly polarized in an atmospheric environment, which also enables the ceramic element to have piezoelectric properties.
According to still another embodiment of the present invention, there is provided a method of manufacturing a lead-free piezoelectric ceramic. The method comprises the following steps:
SS1, and ingredients
With K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3、ZrO2And G is a raw material, each raw material being according to the chemical formula (K)aNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)x-GyThe set values of a, b, c, d, e, f, g, j, x and y in the step (a) and (b) are weighed and proportioned,
wherein x is more than or equal to 0 and less than or equal to 0.10, y is more than or equal to 0 and less than or equal to 2.0, a is more than 0 and less than or equal to 0.8, b is more than 0 and less than or equal to 0.8, c is more than or equal to 0 and less than or equal to 0.08, d is more than or equal to 0 and less than or equal to 0.08, e is more than or equal to 0 and less than or equal to 0.06, f is more than or equal to 0 and less than or,
wherein G is selected from one or a mixture of more of rare earth element oxides, CuO and ZnO,
wherein y is a compound (K) occupied by GaNabBicLidNb1-e-f-gSbeTifTagO3)(1-x)(Ba1-jCajZrO3)xMole percent of (c).
Specifically, the raw materials are powder materials. And weighing and proportioning according to the proportional relation of each element in the chemical formula I. G can be one or more of rare earth element oxide, CuO and ZnO. G is used as a sintering aid, and can obviously reduce the sintering temperature of the lead-free piezoelectric ceramic during preparation.
The amount of each raw material can be set by those skilled in the art according to actual needs.
SS2 preparation
SS21, K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、TiO2、Ta2O3、BaCO3、CaCO3、ZrO2And G to obtain a second calcined powder.
In this method, all raw materials are mixed and directly subjected to pre-firing to obtain a second pre-fired powder.
For example, absolute ethanol is added to a mixture of all the raw materials. And fully mixing and grinding the mixture by adopting a ball milling method. For example, the milling time is 20 hours to make the mixture finer and more uniform. After the milling, the mixture was first dried to remove the absolute ethanol. Then, the mixture was subjected to a burn-in. And pre-burning to finally obtain second pre-burning powder. The purpose of the burn-in is as described previously.
Preferably, in the step, the pre-sintering temperature is 850-900 ℃, and the pre-sintering time is 3-8 hours.
SS22, adding granulating agent into the second pre-sintering powder to form powder with good fluidity, and preparing the powder into rough blank with set shape.
Preferably, the granulating agent is an aqueous solution of polyvinyl alcohol, and the mass concentration of the aqueous solution of polyvinyl alcohol is 4-12%.
For example, the blank is formed by a die pressing method, and the size of the obtained rough blank is phi 10 x 2 mm.
SS23, and carrying out glue discharging treatment on the rough blank. The purpose of the glue removal is as described above.
In one example, pre-dumping is first performed with an organic solvent. Optionally, the organic solvent is one of trichloroethylene, carbon tetrachloride, chloroform and acetone.
Then, the rough blank after pre-degumming is subjected to degumming treatment at high temperature so as to completely remove organic matters such as polyvinyl alcohol and the like. The temperature of the glue discharging treatment is 500-700 ℃.
In another example, the green body is directly subjected to a degumming treatment at a high temperature, in which way organic substances such as polyvinyl alcohol can also be excluded.
And SS24, sintering the rough blank after the binder removal treatment to obtain the ceramic element. Sintering may be carried out in an atmospheric sintering furnace. Preferably, the sintering temperature is 920-1120 ℃, and the sintering time is 2-6 hours. Under such sintering conditions, a perovskite-structured ceramic element can be obtained. The ceramic element is represented by compound I. Spontaneous polarization exists in all directions in the crystal of the ceramic element, and no polarity is presented to the outside from the macroscopic view. Regions of the same spontaneous polarization are called electric domains.
SS3, polarization
And polarizing the ceramic element to obtain the lead-free piezoelectric ceramic device. The electric domain of the ceramic element is polarized to change direction, that is, the spontaneous polarization of the electric domain is forced by polarization to be oriented, so that the ceramic element presents polarity.
Preferably, in this step, the method comprises: first, electrodes are plated on the ceramic element to facilitate polarization.
Then, the ceramic element is put into silicone oil and a direct current of 2-4kV/mm is applied to perform polarization for 15-30 minutes.
By polarization, the ceramic element is referred to as a piezoelectric ceramic device having piezoelectric properties.
In other examples, the ceramic element is directly polarized in an atmospheric environment, which also enables the ceramic element to have piezoelectric properties.
In the preparation method provided by the invention, a perovskite structure with a composite A site is constructed by doping Bi and L i elements.
Further, by introducing Ba1-jCajZrO3The orthogonal-tetragonal phase transition temperature of the potassium-sodium bismuth niobate can be reduced to room temperature, so that the lead-free piezoelectric ceramic has good piezoelectric performance.
In addition, Sb is introduced to reduce the orthorhombic-tetragonal phase transition temperature of the potassium-sodium niobate to room temperature and simultaneously increase the trigonal-tetragonal phase transition temperature to room temperature, and finally, the ceramic with the novel trigonal-tetragonal phase boundary structure is obtained in a room temperature region, so that the temperature stability of the lead-free piezoelectric ceramic is improved.
In addition, the sintering temperature of the lead-free piezoelectric ceramic is lowered by the sintering aid G, so that the reduction of compactness and piezoelectric performance of the ceramic caused by volatilization of alkali metal raw materials under high-temperature sintering is reduced.
Example 1
Prepared by the chemical formula (K)0.48Na0.48Bi0.01Nb0.96Sb0.04O3)0.96(CaZrO3)0.04-(CeO2)yWherein y is 0.75.
The preparation method comprises the following steps:
s1-1, preparing the ingredients
To analytically pure K2CO3、Na2CO3、Bi2O3、Nb2O5、Sb2O3、CaCO3、ZrO2、CeO2The raw materials are weighed and proportioned according to the chemical formula of the corresponding formula.
S2-1 preparation
S21-1, mixing the raw materials (except CeO)2Externally), adding absolute ethyl alcohol, and carrying out primary mixed grinding for 20 hours;
drying the raw materials after the first mixed grinding;
and pre-burning the dried raw materials at 850 ℃ for 5 hours to obtain first pre-burned powder.
S22-1, adding CeO into the first pre-sintering powder2Carrying out secondary mixed grinding with absolute ethyl alcohol for 20 hours;
and drying the powder after the second mixing and grinding to obtain mixed powder.
S23-1, adding a polyvinyl alcohol aqueous solution with the mass concentration of 6% into the mixed powder for granulation, and performing compression molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
S24-1, carrying out degumming treatment on the rough blank at the temperature of 600 ℃.
S25-1, sintering the blank after the binder removal treatment at 1100 ℃ for 4h in an atmosphere sintering furnace to obtain the ceramic element.
S3-1, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil and applying direct current of 3kV/mm for polarization for 30 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was subjected to a performance test after being left to stand at normal temperature for 24 hours. The density of the product is 4.435g/cm3. The piezoelectric coefficient d33 was 220pC/N, and the reverse piezoelectric coefficient d33 ﹡ fluctuated by 7% in the temperature range of room temperature to 170 ℃. The dielectric loss tan was 0.03. The Curie temperature Tc was 414 ℃.
Example 2
Prepared by the chemical formula (K)0.48Na0.48Bi0.01Nb0.96Sb0.04O3)0.96(CaZrO3)0.04-(CeO2)yWherein y is 1.5.
The preparation method comprises the following steps:
s1-2, preparing the ingredients
To analytically pure K2CO3、Na2CO3、Bi2O3、Nb2O5、Sb2O3、CaCO3、ZrO2、CeO2The raw materials are weighed and proportioned according to the chemical formula of the corresponding formula.
S2-2 preparation
S21-2, mixing the raw materials (except CeO)2Externally), adding absolute ethyl alcohol, and carrying out primary mixed grinding for 20 hours;
drying the raw materials after the first mixed grinding;
and pre-burning the dried raw materials at 850 ℃ for 5 hours to obtain first pre-burned powder.
S22-2, adding CeO into the first pre-sintering powder2Carrying out secondary mixed grinding with absolute ethyl alcohol for 20 hours;
and drying the powder after the second mixing and grinding to obtain mixed powder.
S23-2, adding a polyvinyl alcohol aqueous solution with the mass concentration of 6% into the mixed powder for granulation, and performing compression molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
S24-2, firstly, pre-dumping the rough blank in carbon tetrachloride;
then, the binder removal treatment was performed at a temperature of 500 ℃.
And S25-2, sintering the blank subjected to the binder removal treatment at 1100 ℃ for 4h in an atmospheric sintering furnace to obtain the ceramic element.
S3-2, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil and applying direct current of 3kV/mm for polarization for 30 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was subjected to a performance test after being left to stand at normal temperature for 24 hours. The density of the product is 4.385g/cm3. The piezoelectric coefficient d33 is 168pC/N, and the reverse piezoelectric coefficient d33 ﹡ has a fluctuation of 9% in a temperature range from room temperature to 170 ℃. The dielectric loss tan was 0.04. The Curie temperature Tc was 395 ℃.
Example 3
Prepared by the chemical formula (K)0.48Na0.48Bi0.01Nb0.96Sb0.02Ti0.02O3)0.96(Ba0.5Ca0.5ZrO3)0.04-(CuO)yWherein y is 1.5.
The preparation method comprises the following steps:
s1-3, preparing the ingredients
To analytically pure K2CO3、Na2CO3、Bi2O3、Nb2O5、Sb2O3、TiO2、BaCO3、CaCO3、ZrO2And CuO is used as a raw material, and the raw material is weighed and mixed according to a chemical formula of a corresponding formula.
S2-3, preparation
S21-3, adding absolute ethyl alcohol into the prepared raw materials (except CuO), and carrying out first mixed grinding for 20 hours;
drying the raw materials after the first mixed grinding;
and pre-burning the dried raw materials at 800 ℃ for 5 hours to obtain first pre-burned powder.
S22-3, adding CuO and absolute ethyl alcohol into the first pre-sintered powder for secondary mixed grinding, wherein the mixed grinding time is 20 hours;
and drying the powder after the second mixing and grinding to obtain mixed powder.
S23-3, adding a polyvinyl alcohol aqueous solution with the mass concentration of 4% into the mixed powder for granulation, and performing compression molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
S24-3, firstly, pre-degumming the rough blank in chloroform;
then, the binder removal treatment was performed at a temperature of 700 ℃.
And S25-3, sintering the blank subjected to the binder removal treatment at 1020 ℃ for 4h in an atmospheric sintering furnace to obtain the ceramic element.
S3-3, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil, and applying direct current of 4kV/mm for polarization for 15 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was subjected to a performance test after being left to stand at normal temperature for 24 hours. The density of the product is 4.183g/cm3. The piezoelectric coefficient d33 is 264pC/N, and the reverse piezoelectric coefficient d33 ﹡ has a fluctuation of 10% in a temperature range from room temperature to 170 ℃. The dielectric loss tan was 0.03. The Curie temperature Tc was 380 ℃.
Example 4
Prepared by the chemical formula (K)0.48Na0.48Bi0.01Nb0.96Sb0.02Ta0.02O3)0.96(Ba0.5Ca0.5ZrO3)0.04-(ZnO)yWherein y is 1.5.
The preparation method comprises the following steps:
s1-4, preparing the ingredients
To analytically pure K2CO3、Na2CO3、Bi2O3、Nb2O5、Sb2O3、Ta2O3、BaCO3、CaCO3、ZrO2And ZnO is used as a raw material, and the materials are weighed according to the chemical formula of the corresponding formula.
S2-4, preparation
S21-4, adding absolute ethyl alcohol into the prepared raw materials (except ZnO), and carrying out primary mixed grinding for 20 hours;
drying the raw materials after the first mixed grinding;
and pre-burning the dried raw materials at 800 ℃ for 5 hours to obtain first pre-burned powder.
S22-4, adding ZnO and absolute ethyl alcohol into the first pre-sintering powder for secondary mixed grinding, wherein the mixed grinding time is 20 hours;
and drying the powder after the second mixing and grinding to obtain mixed powder.
S23-4, adding a polyvinyl alcohol aqueous solution with the mass concentration of 12% into the mixed powder for granulation, and performing compression molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
S24-4, firstly, pre-degumming the rough blank in chloroform;
then, the resist stripping treatment was performed at a temperature of 550 ℃.
And S25-4, sintering the blank subjected to the binder removal treatment at 920 ℃ for 6 hours in an atmospheric sintering furnace to obtain the ceramic element.
S3-4, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil and applying direct current of 2kV/mm for polarization for 30 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was subjected to a performance test after being left to stand at normal temperature for 24 hours. The density of the powder is 4.120g/cm3. The piezoelectric coefficient d33 is 264pC/N, and the reverse piezoelectric coefficient d33 ﹡ has a fluctuation of 8% in a temperature range from room temperature to 170 ℃. The dielectric loss tan was 0.04. The Curie temperature Tc was 395 ℃.
Example 5
Prepared by the chemical formula (K)0.46Na0.47Bi0.02Nb0.96Sb0.04O3)0.96(CaZrO3)0.04-(ZnO)yWherein y is 1.0.
The preparation method comprises the following steps:
s1-5, preparing the ingredients
To analytically pure K2CO3、Na2CO3、Bi2O3、Nb2O5、Sb2O3、CaCO3、ZrO2And ZnO is used as a raw material, and the materials are weighed according to the chemical formula of the corresponding formula.
S2-5, preparation
S21-5, adding absolute ethyl alcohol into the prepared raw materials (except ZnO), and carrying out primary mixed grinding for 20 hours;
drying the raw materials after the first mixed grinding;
and pre-burning the dried raw materials at 800 ℃ for 5 hours to obtain first pre-burned powder.
S22-5, adding ZnO and absolute ethyl alcohol into the first pre-sintered powder for secondary mixed grinding, wherein the mixed grinding time is 20 hours;
and drying the powder after the second mixing and grinding to obtain mixed powder.
S23-5, adding a polyvinyl alcohol aqueous solution with the mass concentration of 8% into the mixed powder for granulation, and performing compression molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
S24-5, firstly, pre-degumming the rough blank in chloroform;
then, the binder removal treatment was performed at a temperature of 660 ℃.
And S25-5, sintering the blank subjected to the binder removal treatment at 1120 ℃ for 2h in an atmospheric sintering furnace to obtain the ceramic element.
S3-5, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil and applying direct current of 2kV/mm for polarization for 30 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was subjected to a performance test after being left to stand at normal temperature for 24 hours. The density of the product is 4.260g/cm3. The piezoelectric coefficient d33 was 286pC/N, and the reverse piezoelectric coefficient d33 ﹡ fluctuated by 9% in the temperature range of room temperature to 170 ℃. The dielectric loss tan was 0.036. The Curie temperature Tc was 415 ℃.
Example 6
Prepared by the chemical formula (K)0.5Na0.5Nb0.96Sb0.04O3)0.96(Ba0.5Ca0.5ZrO3)0.04-(ZnO)yWherein y is 1.0.
The preparation method comprises the following steps:
s1-6, preparing the ingredients
To analytically pure K2CO3、Na2CO3、Nb2O5、Sb2O3、BaCO3、CaCO3、ZrO2And ZnO is used as a raw material, and the materials are weighed according to the chemical formula of the corresponding formula.
S2-6 preparation
S21-6, adding absolute ethyl alcohol into the prepared raw materials (except ZnO), and carrying out primary mixed grinding for 20 hours;
drying the raw materials after the first mixed grinding;
and pre-burning the dried raw materials at 800 ℃ for 5 hours to obtain first pre-burned powder.
S22-6, adding ZnO and absolute ethyl alcohol into the first pre-sintered powder for secondary mixed grinding, wherein the mixed grinding time is 20 hours;
and drying the powder after the second mixing and grinding to obtain mixed powder.
S23-6, adding a polyvinyl alcohol aqueous solution with the mass concentration of 12% into the mixed powder for granulation, and performing compression molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
S24-6, firstly, pre-degumming the rough blank in acetone;
then, the binder removal treatment was performed at a temperature of 700 ℃.
And S25-6, sintering the blank subjected to the binder removal treatment at 1020 ℃ for 2 hours in an atmospheric sintering furnace to obtain the ceramic element.
S3-6, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil and applying direct current of 3kV/mm for polarization for 30 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was subjected to a performance test after being left to stand at normal temperature for 24 hours. The density of the product is 4.260g/cm3. The piezoelectric coefficient d33 was 280pC/N, and the reverse piezoelectric coefficient d33 ﹡ fluctuated by 7% in the temperature range of room temperature to 170 ℃. The dielectric loss tan was 0.03. The Curie temperature Tc was 397 ℃.
Example 7
Prepared by the chemical formula (K)0.47Na0.47Bi0.01Li0.02Nb0.96Sb0.02Ta0.02O3)0.96(Ba0.5Ca0.5ZrO3)0.04-(ZnO)yWherein y is 1.0.
The preparation method comprises the following steps:
s1-7, preparing the ingredients
To analytically pure K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、Ta2O3、BaCO3、CaCO3、ZrO2And ZnO is used as a raw material, and the materials are weighed according to the chemical formula of the corresponding formula.
S2-7, preparation
S21-7, adding absolute ethyl alcohol into the prepared raw materials (except ZnO), and carrying out primary mixed grinding for 20 hours;
drying the raw materials after the first mixed grinding;
and pre-burning the dried raw materials at 800 ℃ for 5 hours to obtain first pre-burned powder.
S22-7, adding ZnO and absolute ethyl alcohol into the first pre-sintered powder, and performing secondary mixed grinding for 20 hours;
and drying the powder after the second mixing and grinding to obtain mixed powder.
S23-7, adding a polyvinyl alcohol aqueous solution with the mass concentration of 12% into the mixed powder for granulation, and performing compression molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
S24-7, firstly, pre-discharging glue from the rough blank in trichloroethylene;
then, the binder removal treatment was performed at a temperature of 620 ℃.
And S25-7, sintering the blank subjected to the binder removal treatment at 1020 ℃ for 4 hours in an atmospheric sintering furnace to obtain the ceramic element.
S3-7, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil and applying direct current of 2kV/mm for polarization for 30 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was subjected to a performance test after being left to stand at normal temperature for 24 hours. The density of the product is 4.220g/cm3. The piezoelectric coefficient d33 was 280pC/N, and the reverse piezoelectric coefficient d33 ﹡ fluctuated by 9% in the temperature range from room temperature to 170 ℃. The dielectric loss tan was 0.04. The Curie temperature Tc was 389 ℃.
Example 8
Prepared by the chemical formula (K)0.47Na0.47Bi0.01Li0.02Nb0.96Sb0.02Ta0.02O3)0.96(Ba0.5Ca0.5ZrO3)0.04-(ZnO)yWherein y is 1.0.
The preparation method comprises the following steps:
SS1-8, and ingredients
To analytically pure K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、Ta2O3、BaCO3、CaCO3、ZrO2And ZnO is used as a raw material, and the materials are weighed according to the chemical formula of the corresponding formula.
SS2-8, preparation
SS21-8, adding absolute ethyl alcohol into the prepared raw materials, and carrying out mixed grinding for 20 hours;
drying the mixed and ground raw materials;
and pre-burning the dried raw materials at 800 ℃ for 5 hours to obtain second pre-burned powder.
SS22-8, adding a polyvinyl alcohol aqueous solution with the mass concentration of 12% into the second pre-sintering powder for granulation, and performing compression molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
SS23-8, and performing gel discharging treatment at the temperature of 620 ℃.
SS24-8, sintering the blank after the binder removal treatment at 1020 ℃ for 4h in an atmosphere sintering furnace to obtain the ceramic element.
SS3-8, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil and applying direct current of 2kV/mm for polarization for 30 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was subjected to a performance test after being left to stand at normal temperature for 24 hours. The density of the powder is 4.120g/cm3. The piezoelectric coefficient d33 was 268pC/N, and the reverse piezoelectric coefficient d33 ﹡ fluctuated by 9% in the temperature range of room temperature to 170 ℃. The dielectric loss tan was 0.043. Curie temperature Tc of 399℃。
Example 9
Prepared by the chemical formula (K)0.47Na0.47Bi0.01Li0.02Nb0.96Sb0.02Ta0.02O3)0.96(Ba0.5Ca0.5ZrO3)0.04-(CuO)yWherein y is 1.0.
The preparation method comprises the following steps:
SS1-9, and ingredients
To analytically pure K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、Ta2O3、BaCO3、CaCO3、ZrO2And CuO is used as a raw material, and the raw material is weighed and mixed according to a chemical formula of a corresponding formula.
SS2-9 preparation
SS21-9, adding absolute ethyl alcohol into the prepared raw materials, and carrying out mixed grinding for 20 hours;
drying the mixed and ground raw materials;
and pre-burning the dried raw materials at 800 ℃ for 5 hours to obtain second pre-burned powder.
And SS22-9, adding a polyvinyl alcohol aqueous solution with the mass concentration of 8% into the second pre-sintered powder for granulation, and performing compression molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
SS23-9, and performing degumming treatment at 600 ℃.
SS24-9, sintering the blank after the binder removal treatment at 1020 ℃ for 4h in an atmospheric sintering furnace to obtain the ceramic element.
SS3-9, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil and applying direct current of 3kV/mm for polarization for 30 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was allowed to stand at normal temperature for 24 hours, and then subjected to a performance test. The density of the powder is 4.120g/cm3. The piezoelectric coefficient d33 is 258pC/N, and the reverse piezoelectric coefficient d33 ﹡ has a fluctuation of 10% in a temperature range from room temperature to 170 ℃. The dielectric loss tan was 0.04. The Curie temperature Tc was 379 ℃.
Example 10
Prepared by the chemical formula (K)0.47Na0.47Bi0.01Li0.02Nb0.96Sb0.02Ta0.02O3)0.96(Ba0.5Ca0.5ZrO3)0.04-(CeO2)yWherein y is 1.0.
The preparation method comprises the following steps:
SS1-10, compounding
To analytically pure K2CO3、Na2CO3、Bi2O3、Li2CO3、Nb2O5、Sb2O3、Ta2O3、BaCO3、CaCO3、ZrO2、CeO2The raw materials are weighed and proportioned according to the chemical formula of the corresponding formula.
SS2-10, preparation
SS21-10, adding absolute ethyl alcohol into the prepared raw materials, and carrying out mixed grinding for 20 hours;
drying the mixed and ground raw materials;
and pre-burning the dried raw materials at 800 ℃ for 5 hours to obtain second pre-burned powder.
SS22-10, adding a polyvinyl alcohol aqueous solution with the mass concentration of 12% into the second pre-sintering powder for granulation, and pressing and molding by using a mold to obtain a rough blank with phi 10 x 2 mm.
SS23-10, and performing degumming treatment at 700 ℃.
SS24-10, sintering the blank after the binder removal treatment at 1020 ℃ for 4h in an atmosphere sintering furnace to obtain the ceramic element.
SS3-10, polarization
Firstly, plating electrodes on a ceramic element; and then putting the piezoelectric ceramic into silicon oil and applying direct current of 2kV/mm for polarization for 30 minutes to obtain the lead-free piezoelectric ceramic device.
In this example, the obtained lead-free piezoelectric ceramic device was subjected to a performance test after being left to stand at normal temperature for 24 hours. The density of the product is 4.020g/cm3. The piezoelectric coefficient d33 was 240pC/N, and the reverse piezoelectric coefficient d33 ﹡ fluctuated by 9% in the temperature range of room temperature to 170 ℃. The dielectric loss tan is 0.041. The Curie temperature Tc was 385 ℃.
Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.