A lead-free antiferroelectric ceramic, a preparation method and applications thereof

Abstract

The application relates to the field of antiferroelectric ceramic materials and discloses a lead-free antiferroelectric ceramic, a preparation method and application thereof. The chemical composition of the ceramic is (1-x-y)NaNbO3-xABO3-yLa2O3-zMnO2, wherein A is one of Ca, Sr and Ba, B is one of Hf, Zr, Sn and Ti, 0.1<=x<=0.2, 0.05<=y<=0.1 and 0.01<=z<=0.03. The ceramic is a sodium niobate-based antiferroelectric ceramic. The capacitance density of the ceramic increases with the increase of an applied electric field intensity (0-20 kV / mm). The maximum capacitance density change amplitude of a pulse capacitor element made of the ceramic is less than 8% with the increase of working temperature under alternating-current and direct-current coupling electric field (alternating-current electric field 8-10 kV / mm and direct-current electric field 18-20 kV / mm), and the temperature stability of the lead-free antiferroelectric ceramic is significantly increased.

Description

Technical Field

[0001] This invention relates to the field of antiferroelectric ceramic materials, and in particular to a lead-free antiferroelectric ceramic, its preparation method, and its application. Background Technology

[0002] Antiferroelectric ceramics are a class of functional ceramic materials with an antiferroelectric ordered structure and unique electroinduced phase transition properties. Their core characteristic is the ability to undergo a reversible antiferroelectric-ferroelectric phase transition under an electric field, thus exhibiting excellent energy storage and electrostrain properties, making them important for applications in pulsed power devices, energy storage, and actuators. Traditional antiferroelectric ceramics are mainly lead zirconate-based antiferroelectric ceramics. However, since lead zirconate-based antiferroelectric ceramics contain lead, they cause serious environmental problems. Therefore, those skilled in the art have disclosed a niobate-based lead-free antiferroelectric ceramic; for example, publication number CN114956817A discloses a high-energy-density sodium silver niobate-based lead-free antiferroelectric ceramic material and its preparation method.

[0003] Furthermore, lead zirconate-based antiferroelectric ceramics suffer from poor temperature stability due to their low Curie temperature and low AC voltage tolerance (0-1 kV / mm), making them unsuitable for high AC electric fields and high-temperature environments. Niobate-based lead-free antiferroelectric ceramics, on the other hand, possess a higher Curie temperature, allowing them to be used in high-temperature environments. Moreover, prior art CN118515482A discloses a sodium niobate-based dielectric ceramic whose capacitance decreases with increasing applied electric field (0~105 kV / cm), indicating a significant decrease in capacitance density under high voltage conditions. Therefore, further research is needed to obtain a sodium niobate-based dielectric ceramic that is both high-voltage and high-temperature resistant. Summary of the Invention

[0004] This invention provides a lead-free antiferroelectric ceramic, which is a sodium niobate-based antiferroelectric ceramic, and the capacitance density of the ceramic increases with the increase of the applied electric field strength.

[0005] The capacitor element made of sodium niobate-based antiferroelectric ceramic, when placed under an applied AC / DC coupled electric field (8~10 kV / mm AC field and 18~20 kV / mm DC field), shows that the maximum capacitance density of the ceramic changes by less than 8% with increasing operating temperature, and the temperature sensitivity of the lead-free antiferroelectric ceramic is significantly reduced.

[0006] The specific technical solution of this invention is as follows:

[0007] A lead-free antiferroelectric ceramic with the chemical composition (1-xy)NaNbO3-xABO3-yLa2O3-zMnO2, wherein A is one of Ca, Sr and Ba, B is one of Hf, Zr, Sn and Ti, and 0.1≤x≤0.2, 0.05≤y≤0.1, 0.01≤z≤0.03.

[0008] This invention provides a lead-free antiferroelectric ceramic with the chemical formula (1-xy)NaNbO3-xABO3-yLa2O3-zMnO2. The ceramic is doped with elements such as Ca, Sr, Ba, Hf, Zr, Sn and Ti. When an applied AC current of 0~20 kV / mm is applied, the capacitance density of the ceramic increases with the increase of the electric field strength.

[0009] A method for preparing the above-mentioned lead-free antiferroelectric ceramic includes the following steps: ball milling raw materials, ball milling material and anhydrous ethanol, drying, sieving and pre-firing the slurry after ball milling to prepare a pre-fired material; ball milling the pre-fired material, ball milling material and anhydrous ethanol, drying the slurry after ball milling to prepare a powder; pressing the powder into a green body, and calcining the green body to prepare the lead-free antiferroelectric ceramic.

[0010] As a preferred option, the pre-firing conditions are: temperature 900~1000 ℃, time 4~6 h.

[0011] Preferably, the mass ratio of the grinding ball, the raw material, and anhydrous ethanol is 1~3:1:3~5, and the grinding ball is zirconium oxide.

[0012] Preferably, the mass ratio of the ball milling material, the pre-calcined material, and anhydrous ethanol is 1~3:1:3~5, and the ball milling material is zirconium oxide.

[0013] Preferably, cold isostatic pressing is used for pressing.

[0014] Preferably, the calcination conditions include a temperature of 900~1100 ℃.

[0015] As a preferred option, the calcination conditions also include: pressure of 50~70 MPa and holding pressure for 1~2 h.

[0016] The present invention also provides a method for preparing the above-mentioned lead-free antiferroelectric ceramic, wherein the calcination method in the method adopts hot pressing calcination, which can improve the pressure resistance of the ceramic.

[0017] One application of the above-mentioned lead-free antiferroelectric ceramic in the preparation of pulse capacitors involves fabricating the lead-free antiferroelectric ceramic into a ceramic disc, setting electrode layers on both sides of the ceramic disc to form a pulse capacitor element, and placing the pulse capacitor element in an AC or DC electric field, wherein the AC electric field is 8~10 kV / mm, the DC electric field is 18~20 kV / mm, and the temperature is 25~140 ℃.

[0018] Preferably, the electrode layer is made of silver and has a thickness of 0.09~0.11 mm.

[0019] The present invention also provides the application of the above-mentioned lead-free antiferroelectric ceramic in the preparation of pulse capacitors. The present invention found that when the pulse capacitor element made of the above-mentioned lead-free antiferroelectric ceramic is placed under the conditions of an AC electric field (8~10 kV / mm) and an external bias DC electric field (18~20 kV / mm), the capacitance density change of the lead-free antiferroelectric ceramic at a temperature of 25~140 ℃ is further reduced to less than 8%, and the temperature sensitivity of the lead-free antiferroelectric ceramic is further reduced.

[0020] Compared with the prior art, this application has the following technical effects:

[0021] (1) The chemical formula of the lead-free antiferroelectric ceramic of the present invention is (1-xy)NaNbO3-xABO3-yLa2O3-zMnO2. The ceramic is a sodium niobate-based antiferroelectric ceramic. The capacitance density of the ceramic increases with the increase of the applied electric field strength (0~20 kV / mm).

[0022] (2) The pulse capacitor element made of lead-free antiferroelectric ceramic provided by the present invention, under AC-DC coupled electric field (AC electric field 8~10 kV / mm, DC electric field 18~20 kV / mm), the maximum capacitance density of the ceramic changes by less than 8% with the increase of working temperature. The temperature stability of lead-free antiferroelectric ceramic is significantly increased and the temperature sensitivity is significantly reduced. Attached Figure Description

[0023] Figure 1 This is a capacitance density graph of the lead-free antiferroelectric ceramic of Example 1 as a function of temperature.

[0024] Figure 2 The maximum capacitance density of the lead-free antiferroelectric ceramics in Examples 2 to 8 varies with temperature. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments.

[0026] To better understand the content of this invention, further explanation is provided below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of this invention.

[0027] Example 1:

[0028] A lead-free antiferroelectric ceramic includes the following steps:

[0029] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, zirconium dioxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. The slurry is dried in an oven at 120 ℃ and then passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 900 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0030] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0031] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 900 °C for 1 h to produce lead-free antiferroelectric ceramics.

[0032] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0033] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0034] (b) Test the capacitance density of the silver-plated ceramic disc under the working temperature of 0~140 ℃ and calculate the capacitance density.

[0035] Example 2:

[0036] A lead-free antiferroelectric ceramic includes the following steps:

[0037] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, zirconium dioxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. The slurry is dried in an oven at 120 ℃ and then passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 900 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0038] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0039] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 900 °C for 1 h to produce lead-free antiferroelectric ceramics.

[0040] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0041] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0042] (b) Apply an AC / DC coupled electric field (AC field 8 kV / mm, DC field 20 kV / mm) to the silver-plated ceramic disc, test the capacitance density of the silver-plated ceramic disc under the working temperature of 25℃, and calculate the maximum capacitance density.

[0043] Example 3:

[0044] A lead-free antiferroelectric ceramic includes the following steps:

[0045] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, zirconium dioxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. The slurry is dried in an oven at 120 ℃ and then passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 900 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0046] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0047] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 900 °C for 1 h to produce lead-free antiferroelectric ceramics.

[0048] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0049] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0050] (b) Apply an AC / DC coupled electric field (AC field 8 kV / mm, DC field 20 kV / mm) to the silver-plated ceramic disc, test the capacitance density of the silver-plated ceramic disc under the working temperature of 40 ℃, and calculate the maximum capacitance density.

[0051] Example 4:

[0052] A lead-free antiferroelectric ceramic includes the following steps:

[0053] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, zirconium dioxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. The slurry is dried in an oven at 120 ℃ and then passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 900 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0054] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0055] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 900 °C for 1 h to produce lead-free antiferroelectric ceramics.

[0056] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0057] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0058] (b) Apply an AC / DC coupled electric field (AC field 8 kV / mm, DC field 20 kV / mm) to the silver-plated ceramic disc, test the capacitance density of the silver-plated ceramic disc under the working temperature of 60 ℃, and calculate the maximum capacitance density.

[0059] Example 5:

[0060] A lead-free antiferroelectric ceramic includes the following steps:

[0061] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, zirconium dioxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. The slurry is dried in an oven at 120 ℃ and then passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 900 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0062] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0063] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 900 °C for 1 h to produce lead-free antiferroelectric ceramics.

[0064] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0065] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0066] (b) Apply an AC / DC coupled electric field (AC field 8 kV / mm, DC field 20 kV / mm) to the silver-plated ceramic disc, test the capacitance density of the silver-plated ceramic disc under the working temperature of 80 ℃, and calculate the maximum capacitance density.

[0067] Example 6:

[0068] A lead-free antiferroelectric ceramic includes the following steps:

[0069] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, zirconium dioxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. The slurry is dried in an oven at 120 ℃ and then passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 900 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0070] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0071] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 900 °C for 1 h to produce lead-free antiferroelectric ceramics.

[0072] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0073] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0074] (b) Apply an AC / DC coupled electric field (AC field 8 kV / mm, DC field 20 kV / mm) to the silver-plated ceramic disc, test the capacitance density of the silver-plated ceramic disc under the working temperature of 100 ℃, and calculate the maximum capacitance density.

[0075] Example 7:

[0076] A lead-free antiferroelectric ceramic includes the following steps:

[0077] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, zirconium dioxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. The slurry is dried in an oven at 120 ℃ and then passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 900 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0078] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0079] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 900 °C for 1 h to produce lead-free antiferroelectric ceramics.

[0080] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0081] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0082] (b) Apply an AC / DC coupled electric field (AC field 8 kV / mm, DC field 20 kV / mm) to the silver-plated ceramic disc, test the capacitance density of the silver-plated ceramic disc under the working temperature of 120 ℃, and calculate the maximum capacitance density.

[0083] Example 8:

[0084] A lead-free antiferroelectric ceramic includes the following steps:

[0085] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, zirconium dioxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. The slurry is dried in an oven at 120 ℃ and then passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 900 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0086] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0087] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 900 °C for 1 h to produce lead-free antiferroelectric ceramics.

[0088] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0089] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0090] (b) Apply an AC / DC coupled electric field (AC field 8 kV / mm, DC field 20 kV / mm) to the silver-plated ceramic disc, test the capacitance density of the silver-plated ceramic disc under the working temperature of 140 ℃, and calculate the maximum capacitance density.

[0091] Example 9:

[0092] A lead-free antiferroelectric ceramic includes the following steps:

[0093] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.8NaNbO3-0.1SrTiO3-0.08La2O3-0.02MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, titanium dioxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. After drying the slurry in an oven at 120 ℃, it is passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 920 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0094] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0095] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 950 °C for 1 h to produce lead-free antiferroelectric ceramics.

[0096] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0097] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0098] (b) Apply an AC / DC coupled electric field (AC field 10 kV / mm, DC field 20 kV / mm) to the silver-plated ceramic disc, test the capacitance density of the silver-plated ceramic disc under the working temperature of 25~140 ℃, and calculate the maximum capacitance density.

[0099] Example 10:

[0100] A lead-free antiferroelectric ceramic includes the following steps:

[0101] (1) Weigh the required raw materials according to the stoichiometric ratio of lead-free antiferroelectric ceramic 0.77NaNbO3-0.15SrHfO3-0.05La2O3-0.03MnO2. The raw materials are sodium carbonate, niobium pentoxide, strontium carbonate, hafnium oxide, lanthanum carbonate and manganese dioxide. Mix the above raw materials, ball milling material and anhydrous ethanol in a mass ratio of 1:2:4 and then ball mill to make a slurry. The ball milling process is 500 rpm for 36 h. After drying the slurry in an oven at 120 ℃, it is passed through a 200-mesh sieve to obtain powder. The powder is placed in a heat treatment furnace and heat-treated at 980 ℃ for 4 h. After cooling, it is ground to make pre-fired material.

[0102] (2) The pre-burned material, ball milling material and anhydrous ethanol are mixed in a mass ratio of 1:2:4 and then ball milled to make a slurry. The ball milling process is carried out at 500 rpm for 36 h. The slurry is then dried in an oven at 120 ℃ to make powder.

[0103] (3) The powder is subjected to isostatic pressing to form a cylindrical blank. The blank is then embedded in the master powder and kept in a hot pressing furnace with an external pressure of 60 MPa and a temperature of 1000 ℃ for 1 h to produce lead-free antiferroelectric ceramics.

[0104] An application of the above-mentioned lead-free antiferroelectric ceramic in the fabrication of a pulse capacitor includes the following steps:

[0105] (a) The above-mentioned lead-free antiferroelectric ceramic is polished into a ceramic disc of 0.3 mm according to the size requirements. Then, a silver layer of 0.1 ± 0.01 mm is plated on both sides of the ceramic raw material. Then, it is placed in a calcining furnace at 400 ℃ and calcined for 30 min to produce a silver-plated ceramic disc.

[0106] (b) Apply an AC / DC coupled electric field (AC field 8 kV / mm, DC field 18 kV / mm) to the silver-plated ceramic disc, test the capacitance density of the silver-plated ceramic disc under the working temperature of 25~140 ℃, and calculate the maximum capacitance density.

[0107] Examples 1 to 8 are lead-free antiferroelectric ceramics consisting of 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2. After testing the capacitance density of this ceramic under different conditions, it was found that when an applied AC electric field of 0~20 KV / mm is applied, the capacitance density of the ceramic increases with the increase of the electric field strength.

[0108] like Figure 1As shown, the capacitance density of the lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2 increases with increasing temperature under the condition of 0~140 ℃ without an external electric field. The increase in capacitance density reaches 10%, and the increasing trend is upward. This result indicates that it has high temperature stability.

[0109] like Figure 2 As shown, this invention also found that when the lead-free antiferroelectric ceramic 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2 is subjected to an external AC / DC coupled electric field (8 kV / mm AC field and 20 kV / mm DC field), under the operating temperature conditions of 25~140 ℃, the maximum capacitance density of the ceramic changes with increasing temperature, showing a fluctuating trend, and the change range of capacitance density is reduced to less than 5%. The temperature sensitivity of the ceramic is significantly reduced, and the high-temperature stability is significantly increased.

[0110] In addition, the present invention provides two types of lead-free antiferroelectric ceramics: 0.8NaNbO3-0.1SrTiO3-0.08La2O3-0.02MnO2 (Example 9) and 0.77NaNbO3-0.15SrHfO3-0.05La2O3-0.03MnO2 (Example 10), and the capacitance density of these two types of lead-free antiferroelectric ceramics was also tested. Test results showed that the capacitance density of the lead-free antiferroelectric ceramic 0.8NaNbO3-0.1SrTiO3-0.08La2O3-0.02MnO2 increased when an external AC electric field of 0~20 KV / mm was applied. The capacitance density of the lead-free antiferroelectric ceramic 0.77NaNbO3-0.15SrHfO3-0.05La2O3-0.03MnO2 also increased when an external AC electric field of 0~20 KV / mm was applied. The above results indicate that the lead-free antiferroelectric ceramics prepared in Examples 9 and 10 have the same characteristics as the ceramics prepared in Examples 1 to 8.

[0111] Furthermore, when AC / DC coupled electric fields were applied to the lead-free antiferroelectric ceramics of Examples 9 and 10, it was found that the ceramic of Example 9, under AC / DC coupled electric fields (10 kV / mm AC and 20 kV / mm DC) and operating temperatures of 25–140 °C, showed a fluctuating trend in maximum capacitance density with increasing temperature, with a change range of 8%. The ceramic of Example 10, under AC / DC coupled electric fields (8 kV / mm AC and 18 kV / mm DC) and operating temperatures of 25–140 °C, also showed a fluctuating trend in maximum capacitance density with increasing temperature, with a change range of 3%. These results indicate that compositional design can improve the temperature stability and maximum capacitance density under AC / DC coupling conditions of sodium niobate-based lead-free antiferroelectric ceramics.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for using a lead-free antiferroelectric ceramic in the manufacture of pulse capacitors, characterized in that, The lead-free antiferroelectric ceramic is made into a ceramic wafer, an electrode layer is arranged on the two sides of the ceramic wafer to make a pulse capacitor element, and the pulse capacitor element is used in an alternating current electric field and a direct current electric field, the alternating current electric field is 8-10 kV / mm, the direct current electric field is 18-20 kV / mm, and the temperature is 25-140 DEG C; the chemical composition of the lead-free antiferroelectric ceramic is: 0.84NaNbO3-0.1SrZrO3-0.05La2O3-0.01MnO2 or 0.8NaNbO3-0.1SrTiO3-0.08La2O3-0.02MnO2 or 0.77NaNbO3-0.15SrHfO3-0.05La2O3-0.03MnO2.

2. The method of using the lead-free antiferroelectric ceramic according to claim 1, characterized by, The preparation of the lead-free antiferroelectric ceramic comprises the following steps: ball milling raw materials, ball milling materials and anhydrous ethanol, drying the slurry after ball milling, screening and pre-burning the pre-burned material to make a pre-burned material; ball milling the pre-burned material, ball milling materials and anhydrous ethanol, drying the slurry after ball milling to make a powder material; pressing the powder material into a green body, and calcining the green body to make a lead-free antiferroelectric ceramic.

3. The use according to claim 2, characterized in that The pre-burning conditions are: temperature 900-1000 DEG C, time 4-6 h.

4. The method of claim 2 wherein the step of applying comprises, The mass ratio of the ball milling material, the raw material and the anhydrous ethanol is 1-3:1:3-5, and the ball milling material is zirconium oxide.

5. The method of claim 2 wherein the step of applying comprises, The mass ratio of the ball milling material, the pre-burned material and the anhydrous ethanol is 1-3:1:3-5, and the ball milling material is zirconium oxide.

6. The method of claim 2 wherein the step of applying comprises, Cold isostatic pressing is adopted for pressing.

7. The use according to claim 2, characterized in that, The calcining conditions include: temperature 900-1100 DEG C.

8. The use according to claim 2 or 7, characterized in that The calcining conditions also include: pressure 50-70 MPa, and pressure maintaining time 1-2 h.

9. The use according to claim 1, characterized in that The material of the electrode layer is silver, and the thickness of the electrode layer is 0.09-0.11 mm.

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