A barium strontium titanate-based solid-state electric caloric refrigeration lead-free multilayer ceramic material and a low-temperature synthesis preparation method thereof

Abstract

The application discloses a barium strontium titanate-based solid-state electric card refrigeration lead-free multilayer ceramic material and a low-temperature synthesis preparation method thereof, and mainly solves the problems of high sintering temperature, poor structural stability and low electric card performance of an electric card material prepared by using an existing technology. 0.7 Sr 0.3 ) (1‑x) A x Ti (1‑y) B y O3‑ z MO ceramic material, wherein A is an alkaline earth metal element introduced at a material A site, B is a transition metal element introduced at a material B site, M is a trace metal element doped outside, x, y and z are respectively doping amounts of A, B and M; and the inner electrode layer adopts an Ag / Pd alloy electrode. The application has low sintering temperature, good material structural stability, can effectively improve the electric card performance of the material, and is compatible with an existing multilayer ceramic preparation process, and can be used in heat management application scenarios such as microelectronic chips and wearable devices.

Description

Technical Field

[0001] This invention belongs to the field of solid-state refrigeration materials technology, and particularly relates to a lead-free multilayer ceramic material based on barium strontium titanate for solid-state electrothermal refrigeration and its low-temperature synthesis preparation method, which can be used in many thermal management applications such as microelectronic chips, wearable devices and electronic components. Background Technology

[0002] As electronic devices, power modules, and wearable devices become increasingly integrated, the problem of localized heat accumulation is becoming more prominent. Poor heat dissipation not only affects the stability of device performance but also significantly shortens its lifespan. Traditional gas compression refrigeration systems suffer from drawbacks such as large size, complex structure, and reliance on working fluid circulation; while magnetic cards, thermoelectric cooling, and adsorption refrigeration have been applied, they are usually limited by harsh conditions such as strong magnetic fields, large temperature differences, or special materials, and still face many challenges in achieving miniaturization, low power consumption, and environmental friendliness.

[0003] Solid-state cooling, utilizing the entropy and temperature changes of polar materials under an electric field to achieve heat transfer without the need for moving mechanical parts, represents a highly promising solution. Among these, Ba... 1-x Sr x TiO3 (BST) system, with its adjustable Curie temperature, lead-free environmental friendliness, and mature processing technology, is considered an ideal candidate material for achieving room-temperature electrocardiogram (ECG) cooling. However, traditional bulk BST ceramics are typically thick, requiring tens of kilovolts of high voltage to obtain a sufficient electric field, which is not conducive to integration and low-power applications. Mature multilayer ceramic technology can reduce the thickness of a single layer to the micrometer level, thereby achieving a high electric field at low voltage. Through reasonable composition design and low-temperature sintering processes, it is hoped that high-performance, low-operating-voltage BST multilayer ECG ceramics can be prepared, promoting their practical application. However, the sintering temperature of existing BST ceramics is relatively high, mostly above 1250℃, which easily leads to problems such as component volatilization, abnormal grain growth, and poor interlayer bonding, affecting ECG performance. Therefore, it is necessary to develop a method for preparing BST-based lead-free ECG ceramics that combines composition control, multilayer structure design, and low-temperature sintering, to achieve high density while improving its ECG effect and reliability.

[0004] Patent document CN113443910A discloses "a barium strontium titanate ceramic material adapted to base metal internal electrodes and its preparation method." This method introduces acceptor-donor composite doping into a barium strontium titanate matrix and sintersects it under a reducing atmosphere to achieve co-firing matching between the ceramic dielectric and base metal internal electrodes such as nickel, thereby obtaining a multilayer ceramic capacitor material with stable dielectric properties. While this method can solve the matching problem between the ceramic dielectric and the base metal internal electrodes to some extent and meet the application requirements of capacitors, its technical objectives mainly focus on dielectric stability and adaptability to reducing atmosphere sintering, with less attention paid to electrocardiographic cooling characteristics. Furthermore, its material system and sintering process are primarily designed for traditional MLCC dielectric materials, making it difficult to simultaneously accommodate the large polarization change characteristics required for the electrocardiographic effect.

[0005] In summary, existing preparation methods do not adequately address the electrocaloric effect and low-temperature dense sintering characteristics of the materials, making it difficult to simultaneously meet the comprehensive requirements of low sintering temperature, multilayer structural stability, and excellent electrocaloric cooling performance. Therefore, developing a simple process for preparing high-density, multilayer-structured, and excellent electrocaloric barium titanate-based lead-free multilayer ceramic materials at relatively low sintering temperatures, along with its preparation method, is a pressing technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the prior art by providing a lead-free multilayer ceramic material based on barium strontium titanate for solid electrocaloric refrigeration and its low-temperature synthesis preparation method, so as to simultaneously meet the comprehensive requirements of low sintering temperature, multilayer structure stability and excellent electrocaloric refrigeration performance.

[0007] The technical approach to achieving the objective of this invention is as follows: By rationally designing the chemical composition of barium strontium titanate (BST)-based ceramics, introducing various A-site and B-site doping methods as well as trace doping, and combining this with process steps such as pre-firing, tape casting, multilayer lamination, and low-temperature segmented sintering, a lead-free solid-state electro-cooling multilayer ceramic with high density, good interfacial bonding, and high overall electro-cooling performance is obtained at a relatively low sintering temperature of 800~1000 °C. This enables the material to not only possess excellent multilayer ceramic structural stability but also to be applied in the fields of solid-state electro-cooling and thermal management of electronic devices, thus expanding its application prospects.

[0008] Based on the above ideas, the technical solution of the present invention includes:

[0009] 1. A lead-free multilayer ceramic material based on barium strontium titanate solid-state electro-cooling, comprising alternating layers of dielectric and inner dielectric layers.

[0010] Electrode layer, characterized in that:

[0011] The dielectric layer adopts the general formula (Ba 0.7 Sr 0.3) (1-x) A x Ti (1-y) B y O3- z MO ceramic materials are used to improve the electrical performance of materials, where: A is an alkaline earth metal element introduced at site A of the material, B is a transition metal element introduced at site B of the material, M is a trace metal element externally doped, x is the doping amount at site A, y is the doping amount at site B, and z is the doping amount of trace external doping element.

[0012] The inner electrode layer is made of Ag / Pd alloy electrode to reduce sintering costs and improve material sintering compatibility.

[0013] Furthermore, the alkaline earth metal element introduced at the A site includes one or more of La, Ca, and Sm; the transition metal element introduced at the B site includes one or more of Mg, Mn, W, Cu, and Nb; and the externally doped trace metal element M includes one or more of Li, Bi, and Cd.

[0014] Furthermore, the doping amount x at site A ranges from 0.001 to 0.005; the doping amount y at site B ranges from...

[0015] The value is 0.001 to 0.05; the doping amount z of the trace external doping element M is 0.001 to 0.05.

[0016] 2. A low-temperature synthesis method for preparing a lead-free multilayer ceramic material based on barium strontium titanate solid-state electrocaloric refrigeration, characterized in that it comprises:

[0017] (1) According to the general formula (Ba 0.7 Sr 0.3 ) (1-x) A x Ti (1-y) B y O3- z The raw materials for MO are weighed and mixed according to their stoichiometric ratio, wherein 0.001 ≤ x ≤ 0.005, 0.001 ≤ y ≤ 0.05, and 0.001 ≤ z ≤ 0.05;

[0018] (2) The mixed powder obtained in (1) is added to alcohol and ball-milled for 6-8 hours, then dried. The dry powder is then sintered at 700-900 °C for 3-5 hours, cooled and ground into pre-sintered powder.

[0019] (3) After the pre-calcined powder is ball-milled for 10-20 h, it is wet-milled with organic solvent, dispersant, binder, plasticizer and polyvinyl alcohol to obtain the corresponding slurry;

[0020] (4) The ceramic slurry is made into a ceramic green tape with a thickness of 10~30 μm by casting or scraping process. Ag / Pd internal electrode slurry is printed on the ceramic green tape. Several layers of ceramic green tape with printed electrodes are stacked and laminated to obtain a molded blank.

[0021] (5) The shaped green blank is subjected to organic matter removal at 100~550 °C, pre-densification at 550~800 °C, sintering at 800~1000 °C, and then annealed and cooled to room temperature to obtain a sintered body of barium strontium titanate-based multilayer ceramic.

[0022] (6) Prepare metal electrodes at both ends of the multilayer ceramic and perform heat preservation treatment to obtain a lead-free solid-state electro-calorie multilayer ceramic based on barium strontium titanate.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] Firstly, this invention employs the general formula (Ba 0.7 Sr 0.3 ) (1-x) A x Ti (1-y) B y O3- z MO's ceramic material dielectric layer

[0025] By introducing A-site elements, B-site elements, and trace amounts of external oxides into the barium strontium titanate matrix for synergistic doping control, and combining this with a preparation process of pre-sintering—tape casting—multilayer lamination—low-temperature segmented sintering, dense sintering of ceramic materials can be achieved at a relatively low temperature of 800~1000 ℃. Compared to existing technologies for barium strontium titanate multilayer ceramics that generally require higher sintering temperatures, this invention effectively reduces the sintering temperature, minimizes element volatilization and abnormal grain growth, and facilitates the acquisition of multilayer ceramic structures with uniform grains and high density.

[0026] Secondly, this invention employs a tape-stack-laminar process to prepare a multilayer ceramic structure and utilizes synergistic doping of different elements to control the dielectric layer, enabling it to achieve a higher electric field strength at a lower operating voltage. This is beneficial for improving the electrocardiogram effect and reducing the device operating voltage. Meanwhile, since the electrode layer uses Ag / Pd as the internal electrode material, it can reduce the preparation cost and improve the sintering compatibility of the material. The process is simple, stable, and easy to scale up. Attached Figure Description

[0027] Figure 1 A schematic diagram of the structure of the lead-free multilayer ceramic material for strontium barium titanate-based solid-state electric card refrigeration in this invention;

[0028] Figure 2 A schematic diagram of the preparation process of the lead-free multilayer ceramic material for strontium barium titanate-based solid-state electro-calorie refrigeration in this invention;

[0029] Figure 3 Hysteresis loop test diagram of the multilayer ceramic sample of barium strontium titanate-based lead-free electronic card of the present invention;

[0030] Figure 4 The electrocardiogram of the barium strontium titanate-based lead-free multilayer ceramic sample at 360 V. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited to the scope shown in the embodiments. These embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. After reading this specification, those skilled in the art can make various modifications or equivalent substitutions to the present invention, and these modifications or equivalent substitutions also fall within the scope defined by the appended claims.

[0032] Reference Figure 1 The present invention relates to a lead-free multilayer ceramic material based on barium strontium titanate solid-state electro-cooling, comprising alternating layers of multilayer dielectric layers and an inner electrode layer.

[0033] Each of the multiple dielectric layers adopts the general formula (Ba 0.7 Sr 0.3 ) (1-x) A x Ti (1-y) B y O3- z MO is a ceramic material used to improve the electrochemical performance of the material. In this material, A is an alkaline earth metal element introduced at site A, B is a transition metal element introduced at site B, M is a trace metal element externally doped, x is the doping amount at site A, y is the doping amount at site B, and z is the doping amount of the trace external doping element.

[0034] The alkaline earth metal element introduced at site A includes one or more of La, Ca, and Sm;

[0035] The transition metal element introduced at the B site includes one or more of Mg, Mn, W, Cu, and Nb;

[0036] The externally doped trace metal element M includes one or more of Li, Bi, and Cd;

[0037] The doping amount x at site A ranges from 0.001 to 0.005.

[0038] The doping amount y at the B site ranges from 0.001 to 0.05.

[0039] The doping amount z of the trace external doping element M ranges from 0.001 to 0.05.

[0040] Each inner electrode layer in the multilayer inner electrode layer is made of Ag / Pd alloy electrode in a ratio of 10:90 to 40:60, in order to reduce sintering costs and improve the sintering compatibility of materials.

[0041] Reference Figure 2 This invention provides three embodiments for preparing lead-free multilayer ceramic materials for strontium barium titanate-based solid-state electro-cooling.

[0042] Example 1: A dielectric layer was prepared with the following formula: A is selected as La, doping amount x is 0.001, B is selected as Mn, doping amount y is 0.05, M is selected as Li, doping amount z is 0.01, and the thickness is 10 μm. The chemical formula is: (Ba 0.7 Sr 0.3 ) 0.98 La 0.02 Ti 0.95 Mn 0.05 A multilayer ceramic material with O3-0.05Li2O and an internal electrode Ag / Pd ratio of 20:80.

[0043] Step 1, Preparation of (Ba 0.7 Sr 0.3 ) 0.999 La 0.001 Ti 0.95 Mn 0.05 O3-0.01Li2O ceramic powder.

[0044] 1.1) According to the chemical formula (Ba 0.7 Sr 0.3 ) 0.999 La 0.001 Ti 0.95 Mn 0.05 O3-0.011Li2O is produced by weighing powder from high-purity raw materials (≥99.99%): BaCO3, SrCO3, TiO2, La2O3, MnO2 and Li2CO3;

[0045] 1.2) The powder and anhydrous ethanol were loaded into a zirconia ball mill jar at a ratio of 1:1.5 and ball milled for 6 hours. After drying, the mixed powder was obtained.

[0046] 1.3) The mixed powder was placed in an alumina crucible, heated to 700℃ in air atmosphere, held for 3 hours, and then cooled in the furnace to obtain (Ba 0.7 Sr 0.3 ) 0.999 La 0.001 Ti 0.95 Mn 0.05 O3-0.01Li2O ceramic powder.

[0047] Step 2, ball milling casting slurry.

[0048] will (Ba 0.7 Sr 0.3 ) 0.999 La 0.001 Ti 0.95 Mn 0.05 O3-0.01Li2O ceramic powder was lightly ground and sieved. An equal proportion of anhydrous ethanol, dispersant, plasticizer and 6 wt% PVA binder solution were added. The mixture was then placed in a ball mill jar and wet-milled for 10 h to obtain a uniform cast slurry.

[0049] Step 3, Preparation of (Ba 0.7 Sr 0.3 ) 0.999 La 0.001 Ti 0.95 Mn 0.05 O3-0.01Li2O multilayer ceramic material.

[0050] 3.1) Pour the casting slurry into the casting machine, adjust the doctor blade gap to prepare a ceramic green tape with a thickness of about 10 μm, print Ag / Pd internal electrode slurry on the ceramic green tape at a ratio of 20:80, and then press it into a multilayer ceramic green body in a cold isostatic press.

[0051] 3.2) The obtained multilayer ceramic green body was placed in a crucible and heated to 100 °C in air atmosphere, held for 2 h to remove organic matter; then heated to 550 °C and held for 2 h; then heated to 800 °C to complete densification sintering; finally annealed at 550 °C for 1.5 h. A sintered body of barium strontium titanate-based multilayer ceramic with a relative density greater than 95% and an average single-layer thickness of 10 μm was obtained.

[0052] 3.3) Silver electrodes were screen-printed at both ends of the multilayer ceramic sample, and then sintered and solidified at 650 °C for 10 min to obtain (Ba 0.7 Sr 0.3 ) 0.999 La 0.001 Ti 0.95 Mn 0.05 O3-0.05Li2O multilayer ceramic material.

[0053] Example 2: A dielectric layer was prepared with A selected as Ca, doping amount x as 0.005, B selected as Mg, doping amount y as 0.001, M selected as Bi, doping amount z as 0.03, and a thickness of 30 μm. The chemical formula was: (Ba 0.6 Sr 0.4 ) 0.995 Ca 0.005 Ti 0.999 Mg0.001 O3-0.03Bi2O3, a multilayer ceramic material with an internal electrode Ag / Pd ratio of 25:75.

[0054] Step 1, Preparation of (Ba 0.6 Sr 0.4 ) 0.995 Ca 0.005 Ti 0.999 Mg 0.001 O3-0.03Bi2O3 ceramic powder.

[0055] According to the chemical formula (Ba 0.6 Sr 0.4 ) 0.995 Ca 0.005 Ti 0.999 Mg 0.001 O3-0.03Bi2O3 was obtained by weighing powder from high-purity raw materials (≥99.99%): BaCO3, SrCO3, CaCO3, TiO2, MgO, and Bi2O3; then, the powder was mixed with anhydrous ethanol at a ratio of 1:3.5 and ball-milled in a zirconia ball mill jar for 8 hours, and dried to obtain a mixed powder; then, the mixed powder was placed in an alumina crucible and heated to 900℃ in air atmosphere, held at that temperature for 5 hours, and then cooled to room temperature to obtain (Ba 0.6 Sr 0.4 ) 0.995 Ca 0.005 Ti 0.999 Mg 0.001 O3-0.03Bi2O3 ceramic powder.

[0056] Step 2: Ball milling the casting slurry.

[0057] will (Ba 0.6 Sr 0.4 ) 0.995 Ca 0.005 Ti 0.999 Mg 0.001 O3-0.03Bi2O3 powder was lightly ground and sieved. An equal proportion of anhydrous ethanol, dispersant, plasticizer and 10 wt% PVA binder solution were added. The mixture was then placed in a ball mill jar and wet-milled for 20 h to obtain a uniform cast slurry.

[0058] Step 3, Preparation of (Ba 0.6 Sr 0.4 ) 0.995 Ca 0.005 Ti 0.999 Mg 0.001 O3-0.03Bi2O3 multilayer ceramic material.

[0059] The casting slurry is poured into the casting machine, and the doctor blade gap is adjusted to prepare a ceramic green tape with a thickness of about 30 μm. Ag / Pd internal electrode slurry is printed on the ceramic green tape, wherein the ratio of Ag to Pd is 25:75. Then, it is pressed into a multilayer ceramic green body in a cold isostatic press.

[0060] The obtained multilayer ceramic green body was placed in a crucible and heated to 550 °C in air atmosphere, held for 2 h to remove organic matter; then heated to 800 °C and held for 2 h; then heated to 1000 °C to complete densification sintering, and finally annealed at 750 °C for 2 h. A sintered body of barium strontium titanate-based multilayer ceramic with a relative density greater than 95% and an average single-layer thickness of 30 μm was obtained.

[0061] Silver electrodes were screen-printed at both ends of the multilayer ceramic sample, and then sintered and solidified at 650 °C for 10 min to obtain (Ba 0.6 Sr 0.4 ) 0.995 Ca 0.005 Ti 0.999 Mg 0.001 O3-0.03Bi2O3 multilayer ceramic material.

[0062] Example 3, in the preparation of the dielectric layer, A is selected as Sm, the doping amount x is 0.003, B is selected as W, the doping amount y is 0.035, M is selected as Cd, the doping amount z is 0.05, and the chemical formula is: (Ba 0.6 Sr 0.4 ) 0.997 Sm 0.003 Ti 0.965 W 0.035 A multilayer ceramic material with O3-0.05CdO and an internal electrode Ag / Pd ratio of 40:60.

[0063] Step A, prepare (Ba 0.6 Sr 0.4 ) 0.997 Sm 0.003 Ti 0.965 W 0.035 O3-0.05CdO ceramic powder.

[0064] A1) According to the chemical formula (Ba 0.6 Sr 0.4 ) 0.997 Sm 0.003 Ti 0.965 W 0.035 O3-0.05CdO is produced by weighing powder from high-purity raw materials (≥99.99%): BaCO3, SrCO3, Sm2O3, TiO2, WO3, and CdO.

[0065] A2) The powder in a ratio of 1:2 and anhydrous ethanol were placed in a zirconia ball mill jar and ball-milled for 7 h. After drying, the mixed powder was obtained.

[0066] A3) The obtained mixed powder was placed in an alumina crucible, heated to 800℃ in air atmosphere, held for 4 h, and then cooled in the furnace to obtain (Ba 0.6 Sr 0.4 ) 0.997 Sm 0.003 Ti 0.965 W 0.035 O3-0.05CdO powder.

[0067] Step B: Ball milling of casting slurry.

[0068] B1) will (Ba 0.6 Sr 0.4 ) 0.997 Sm 0.003 Ti 0.965 W 0.035 O3-0.05CdO powder was successively ground and sieved to obtain a mixed powder with uniform particle size;

[0069] B2) Add an equal proportion of anhydrous ethanol, dispersant, plasticizer and 8wt% PVA binder solution to the mixed powder with uniform particle size, load it into a ball mill jar and wet ball mill again for 8 h to obtain a uniform cast slurry.

[0070] Step C, prepare (Ba 0.6 Sr 0.4 ) 0.997 Sm 0.003 Ti 0.965 W 0.035 O3-0.05CdO multilayer ceramic material.

[0071] C1) Pour the casting slurry into the casting machine, adjust the doctor blade gap to prepare a ceramic green tape with a thickness of about 20 μm, and print Ag / Pd internal electrode slurry on the ceramic green tape at a ratio of 40:60. Then press it into a multi-layer ceramic green body in a cold isostatic press.

[0072] C2) Fabrication of multi-layered ceramic sintered bodies:

[0073] The obtained multilayer ceramic green body was placed in a crucible and heated to 550 °C in air atmosphere, and held for 2 h to remove organic matter; then heated to 800 °C and held for 2 h; then heated to 1000 °C to complete the densification sintering.

[0074] Finally, the mixture was annealed at 750℃ for 2 h. This yielded a sintered barium strontium titanate-based multilayer ceramic with a relative density greater than 95% and an average single-layer thickness of 20 μm.

[0075] C3) Silver electrodes were screen-printed at both ends of a multilayer ceramic sample, and then sintered and solidified at 650 °C for 10 min to obtain (Ba 0.6 Sr 0.4 ) 0.997 Sm 0.003 Ti 0.965 W 0.035 O3-0.05CdO multilayer ceramic material.

[0076] The effectiveness of this invention can be further illustrated by test results:

[0077] Test 1: A PE test was performed on Embodiment 1 of the present invention, and the results are as follows. Figure 3 As shown. From Figure 3 It can be seen that the multilayer ceramic sample of barium strontium titanate-based lead-free electric card has a polarization intensity of nearly 30 μC / cm under an electric field of 130 kV / cm. 2 .

[0078] Test 2: An electrical card effect test was performed on Embodiment 1 of the present invention, and the results are as follows. Figure 4 As shown, from Figure 4 It can be seen that the lead-free ceramic sample based on barium strontium titanate exhibits an electrocarding effect of 3 K cm / kV at a voltage of 360 V.

[0079] The above test results show that the material obtained by the present invention has excellent electrocardiographic effect.

[0080] The above descriptions are merely a few specific embodiments of the present invention and do not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and detail without departing from the principles and structure of the present invention. For example, in the above examples, the alkaline earth metal element A is selected from Ca, La, and Sm, but any combination thereof can also be selected; the transition metal element B is selected from W, Mg, and Mn, and any combination thereof can also be selected from Cu, Nb, and any combination thereof; the external dopant element M is selected from Cd, Bi, and Li, and any combination thereof can also be selected; the internal electrode is prepared by printing, but spraying and other methods can also be used. However, these modifications and changes based on the concept of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A lead-free multilayer ceramic material based on barium strontium titanate solid-state electro-cooling, comprising alternating dielectric layers and internal electrode layers, characterized in that: The dielectric layer adopts the general formula (Ba 0.7 Sr 0.3 ) (1-x) A x Ti (1-y) B y O3- z MO ceramic materials are used to improve the electrical performance of materials, where: A is an alkaline earth metal element introduced at the A site of the material, B is a transition metal element introduced at the B site of the material, M is a trace metal element externally doped, x is the doping amount at the A site, y is the doping amount at the B site, and z is the doping amount of the trace external doping element. The inner electrode layer is made of Ag / Pd alloy electrode to reduce sintering costs and improve the sintering compatibility of the material.

2. The material according to claim 1, characterized in that: The alkaline earth metal element introduced at site A includes one or more of La, Ca, and Sm. The transition metal element introduced at the B site includes one or more of Mg, Mn, W, Cu, and Nb. The externally doped trace metal element M includes one or more of Li, Bi, and Cd.

3. The material according to claim 1, characterized in that: The doping amount x at site A is between 0.001 and 0.

005. The doping amount y at the B site ranges from 0.001 to 0.

05. The doping amount z of the trace external doping element M is between 0.001 and 0.

05.

4. A low-temperature synthesis method for preparing a lead-free multilayer ceramic material based on barium strontium titanate solid-state electrocaloric refrigeration, characterized in that, include: (1) According to the general formula (Ba 0.7 Sr 0.3 ) (1-x) A x Ti (1-y) B y O3- z The raw materials for MO are weighed and mixed according to their stoichiometric ratio, wherein 0.001 ≤ x ≤ 0.005, 0.001 ≤ y ≤ 0.05, and 0.001 ≤ z ≤ 0.05; (2) The mixed powder obtained in (1) is added to alcohol and ball-milled for 6-8 hours, then dried. The dry powder is then sintered at 700-900 ℃ for 3-5 hours, cooled and ground into pre-sintered powder. (3) After the pre-calcined powder is ball-milled for 10-20 h, it is wet-milled with organic solvent, dispersant, binder, plasticizer and polyvinyl alcohol to obtain the corresponding slurry; (4) The ceramic slurry is made into a ceramic green tape with a thickness of 10~30 μm by casting or scraping process. Ag / Pd internal electrode slurry is printed on the ceramic green tape. Several layers of ceramic green tape with printed electrodes are stacked and laminated to obtain a molded blank. (5) The shaped green blank is subjected to organic matter removal at 100~550 °C, pre-densification at 550~800 °C, sintering at 800~1000 °C, and then annealed and cooled to room temperature to obtain a sintered body of barium strontium titanate-based multilayer ceramic. (6) Prepare metal electrodes at both ends of the multilayer ceramic and perform heat preservation treatment to obtain a lead-free solid-state electro-calorie multilayer ceramic based on barium strontium titanate.

5. The method according to claim 4, characterized in that: The raw materials weighed in (1) include BaCO3, SrCO3, Sm2O3, La2O3, CaCO3, CdO, TiO2, CuO, CdO, WO3, MnO2, Bi2O3 and Li2CO3.

6. The method according to claim 5, characterized in that: Different elements require different raw materials, among which: The raw materials required for alkaline earth metal element A are one or more of Sm2O3, La2O3, and CaCO3; The raw materials required for transition metal element B are one or more of MnO2, CuO, and WO3; The raw materials required for trace external doping element M are one or more of Li2CO3, Bi2O3, and CdO.

7. The method according to claim 4, characterized in that, The ratio of the mixed powder to the added alcohol in (2) is 1:(1.5~3.5).

8. The method according to claim 4, characterized in that: The organic solvent, dispersant, binder and plasticizer added in (3) are in the same proportion, and the mass fraction of polyvinyl alcohol added is 6~10 wt%.

9. The method according to claim 4, characterized in that, In step (4), Ag / Pd internal electrode paste is printed on the ceramic raw tape in a ratio of 10:90 to 40:

60.

10. The method according to claim 4, characterized in that, In step (5), the sintered preform is annealed at a temperature of 550-750 °C for 1.5-2 h.

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