A strontium titanate ceramic material, a grain boundary layer ceramic substrate, its preparation method and application

Abstract

This invention discloses a strontium titanate ceramic material, a grain boundary layer ceramic substrate, its preparation method, and its application. The invention involves mixing SrTiO3 powder with dopants, sintering, grinding, and sieving to obtain raw material A. The dopants are one or more selected from Nb2O5 powder, La2O3 powder, MgO powder, and Nd2O3 powder. SrTiO3 powder and glass powder are mixed, sintered, ground, and sieved to obtain raw material B. Raw material A, raw material B, an adhesive, and an organic solvent are mixed and molded to obtain a film. The film is then subjected to debinding and reduction sintering to obtain the strontium titanate ceramic material. The strontium titanate ceramic material of this invention possesses advantages such as increased grain size, uniform growth, and stable electrical properties, making it suitable for manufacturing high-performance ceramic capacitors and demonstrating broad application potential in the field of electronic components.

Description

Technical Field

[0001] This invention relates to the field of grain boundary layer ceramic materials technology, specifically to a strontium titanate ceramic material, a grain boundary layer ceramic substrate, its preparation method and application. Background Technology

[0002] Strontium titanate (SrTiO3) boundary layer ceramic capacitors (BLCCs) have advantages such as high apparent relative permittivity, excellent microwave characteristics, and high temperature stability, and are widely used in high-frequency bypass circuits and other electronic circuits.

[0003] The high dielectric constant of grain boundary layer ceramic capacitors mainly originates from their grain boundary effect. In actual samples, grain boundaries are formed by complex series and parallel connections of grain boundaries with different barrier properties. Considering that any type of grain boundary can provide a continuous channel for current transport, the electrical performance can be qualitatively interpreted as being formed by these different types of grain boundaries connected in parallel. Since interface effects play a decisive role in CP materials, there are two types of interfaces in the capacitor structure based on polycrystalline CP materials. One is the grain boundary, which is the insulation between semiconductor grains. Due to the Schottky barrier at the grain boundary, the capacitance of this interface is called the internal barrier layer capacitance (IBLC). The dielectric response originates from the interfacial polarization between the two particles. The dielectric constant measured based on the IBLC model can be expressed as:

[0004] ε≈ε b d / t

[0005] Where ε b Let d be the dielectric constant of the grain boundary layer, d be the grain size, and t be the thickness of the grain boundary layer. Therefore, increasing the grain size or decreasing the thickness of the grain boundary layer can effectively improve the effective dielectric constant of the grain boundary layer ceramic capacitor.

[0006] Because strontium titanate ceramics synthesized by solid-state method have high sintering temperatures, the grain size distribution after sintering often exhibits a bimodal pattern. In actual production and application, the dielectric constant is inconsistent. Therefore, in order to obtain strontium titanate ceramics with low loss, high dielectric properties, and reliable performance, it is necessary to optimize the sintering process of strontium titanate ceramics. By controlling the grain growth and growth status, high dielectric and low loss grain boundary layer ceramic capacitors can be obtained. Summary of the Invention

[0007] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the present invention aims to provide a strontium titanate ceramic material, a grain boundary layer ceramic substrate and its preparation method, so that the grown strontium titanate grains are uniform in size and have increased grain diameter.

[0008] Another objective of this invention is to provide a strontium titanate-based grain boundary layer capacitor with high dielectric constant, low loss, high reliability, and high capacitance consistency.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for preparing strontium titanate ceramic material includes the following steps:

[0011] (1) Mix SrTiO3 powder and dopant, calcine, grind and sieve to obtain raw material A; the dopant is one or more of Nb2O5 powder, La2O3 powder, MgO powder and Nd2O3 powder;

[0012] (2) Mix SrTiO3 powder and glass powder, calcine, grind and sieve to obtain raw material B;

[0013] (3) Mix raw material A, raw material B, adhesive and organic solvent, and mold them to obtain a film;

[0014] (4) The membrane is debonded and reduced and sintered to obtain strontium titanate ceramic material.

[0015] Preferably, the sieving in step (1) is through a 400-mesh to 1000-mesh sieve; the particle size of the raw material A is less than 13-40 μm;

[0016] Preferably, the molar ratio of the dopant to SrTiO3 in step (1) is (0.2-1):(99-99.8);

[0017] Preferably, the firing temperature in step (1) is 1200℃~1350℃, the heating rate is 2~5℃ / min, and the holding time is 2~5h.

[0018] Preferably, the glass powder in step (2) is one or more of the following glass materials produced by Asahi Glass Co., Ltd.: GA-13, GA-1, GA-4, and GA-9.

[0019] Preferably, the molar ratio of the glass powder to SrTiO3 in step (2) is (0.6-7):(93-99.4);

[0020] Preferably, the firing temperature in step (2) is 1200℃~1350℃, the heating rate is 2~5℃ / min, and the holding time is 2~5h;

[0021] Preferably, the sieving in step (2) is done through an 80-mesh to 200-mesh sieve, with a particle size of less than 75-180 μm.

[0022] Preferably, the adhesive in step (3) is polyvinyl alcohol; the organic solvent is xylene and anhydrous ethanol, and the mass ratio of xylene and anhydrous ethanol is (10-20):(10-20);

[0023] Preferably, the mass ratio of raw material A to raw material B in step (3) is (0.5-7.5):(50-60);

[0024] Preferably, the total amount of raw material A and raw material B in step (3) is in the mass ratio of the adhesive to (54-67.5):(3.0-5.0);

[0025] Preferably, the total ratio of the organic solvent to raw material A, raw material B, and adhesive in step (3) is (27.5-43):(57-72.5);

[0026] Preferably, the conditions for degreasing in step (4) are: heat preservation at 500-600℃ for 2-4 hours, and heating rate of (1-3)℃ / min;

[0027] Preferably, the reduction firing temperature in step (4) is 1300℃~1400℃, the holding time is 1~3h, and the heating rate is (1~5)℃ / min; the atmosphere for the reduction firing is a hydrogen atmosphere.

[0028] Preferably, the thickness of the strontium titanate ceramic material in step (4) is 0.2 to 0.4 mm.

[0029] The strontium titanate ceramic material prepared by the above preparation method.

[0030] A method for preparing a grain boundary layer ceramic substrate includes the following steps:

[0031] (a) The oxidant dispersion is coated onto the surface of the above-mentioned strontium titanate ceramic material to obtain a strontium titanate ceramic material with an oxide medium film attached.

[0032] (b) Under an oxygen atmosphere, the strontium titanate ceramic material with the oxide medium film attached is subjected to an oxidation heat treatment to obtain a grain boundary layer ceramic substrate.

[0033] Preferably, the oxidant in the oxidant dispersion in step (a) is B2O3-Bi2O3 glass, the mass ratio of B2O3 to Bi2O3 is 1:1 to 1.5, the solvent of the oxidant dispersion is one or more of terpineol, anhydrous ethanol and n-butanol; the mass ratio of the oxidant to the solvent in the oxidant dispersion is 1:(1 to 2); and the coating thickness of the oxidant dispersion is 1 to 10 μm.

[0034] Preferably, the oxidant dispersion is coated on one side surface of the strontium titanate ceramic material.

[0035] Preferably, the oxygen atmosphere in step (b) is a pure oxygen atmosphere; the flow rate of the oxygen atmosphere is (1-5) L / min; the temperature of the oxidation heat treatment is 800-1000℃, the time of the oxidation heat treatment is 1-3h, and the heating rate is 3-5℃ / min.

[0036] The above-described preparation method produces a grain boundary layer ceramic substrate.

[0037] The above-mentioned strontium titanate ceramic materials and grain boundary layer ceramic substrates are used in the fabrication of chip capacitors.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] (1) The present invention uses a rolling process to prepare ceramic materials, which is simple and easy to prepare.

[0040] (2) The grain size of the strontium titanate ceramic material prepared by the present invention has been significantly improved and is more uniform.

[0041] (3) The SrTiO3 grain boundary layer ceramic capacitor finally obtained by the present invention has the advantages of high dielectric constant and low dielectric loss. Attached Figure Description

[0042] Figure 1 The image shows the SEM image of the grains in the STO ceramic material in Comparative Example 1.

[0043] Figure 2 The image shows the SEM image of the grains in the STO ceramic material in Comparative Example 2.

[0044] Figure 3 The image shows the SEM image of the grains in the STO ceramic material in Comparative Example 3.

[0045] Figure 4 This is a SEM image of the grains in the strontium titanate ceramic material in Example 1. Detailed Implementation

[0046] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0047] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available products.

[0048] SrTiO3 was purchased from Maclean's, with a particle size of 5 μm; Nb2O5, La2O3, MgO, and Nd2O3 were purchased from Maclean's, with a particle size less than 10 μm; GA-1 (PbO·B2O3·SiO2), GA-4 (Na2O·B2O3·SiO2), GA-9 (PbO·B2O3·SiO2), and GA-13 (CaO·BaO·SiO2) glass materials were purchased from Asahi Glass, with a particle size of 100 μm; B2O3 material was purchased from Maclean's, with a particle size less than 100 μm. Bi2O3 glass material was purchased from Maclean's, with a particle size less than 100 μm.

[0049] Example 1

[0050] This embodiment provides a strontium titanate ceramic material and a grain boundary layer ceramic substrate, comprising the following raw materials:

[0051] Table 1 Raw material parameters for Example 1

[0052] Raw material A 99.4 0.6 0 0 0 Raw materials (mol%) <![CDATA[SrTiO3]]> GA-1 GA-4 GA-9 GA-13 Raw material B 98 2 0 0 0

[0053] (1) Prepare raw material A and raw material B.

[0054] According to the above formula, the components of raw material A are mixed and calcined at 1350℃ for 3 hours (heating rate 2℃ / min), then ground and sieved (400 mesh) to obtain raw material A (particle size less than 40μm). The components of raw material B are mixed and calcined at 1325℃ for 3 hours (heating rate 2℃ / min), then ground and sieved (80 mesh) to obtain raw material B (particle size less than 180μm).

[0055] (2) Mix raw material A and raw material B with polyvinyl alcohol and organic solvent, and then mold them to obtain a film.

[0056] The mass ratio of raw material A to raw material B is 6:60, and the mass ratio of the total amount of raw material A and raw material B to the mass of polyvinyl alcohol is 66:5. The organic solvent is xylene and anhydrous ethanol, and the mass ratio of xylene to anhydrous ethanol is 14.5:14.5. The mass ratio of the total amount of raw material A, raw material B, and polyvinyl alcohol to the mass of the organic solvent is 71:29.

[0057] (3) The diaphragm is subjected to a two-step process of debinding and reduction sintering to obtain a semiconductor grain ceramic substrate (thickness 0.2 mm). Figure 4 ).

[0058] The adhesive removal conditions were: holding at 600℃ for 2 hours, with a heating rate of 1℃ / min. The substrate reduction firing temperature was 1400℃, holding time was 3 hours, heating rate was 2.5℃ / min, and the atmosphere was hydrogen.

[0059] (4) The oxidant dispersion is coated on the surface of the semiconducting grain ceramic substrate to obtain a semiconducting grain ceramic substrate with an oxide medium film attached.

[0060] The oxidant in the oxidant dispersion is a B2O3-Bi2O3 glass material (B2O3 and Bi2O3 in a mass ratio of 1:1), and the solvent in the oxidant dispersion is anhydrous ethanol. The mass ratio of the oxidant to the solvent in the oxidant dispersion is 1:1. The oxidant and dispersion are uniformly coated on the surface (single-sided) of the strontium titanate ceramic prepared in the previous step, with a thickness of 10 μm.

[0061] (5) Under a pure oxygen atmosphere, the semiconductor grain ceramic substrate with the oxide dielectric film attached is subjected to oxidation heat treatment to form a grain boundary insulating layer, thereby obtaining a grain boundary layer ceramic substrate.

[0062] The flow rate of pure oxygen used in the pure oxygen atmosphere was 2 L / min, the temperature of the oxidation heat treatment was 1000℃, the time of the oxidation heat treatment was 1 h, and the heating rate was 3℃ / min. Finally, a grain boundary layer ceramic substrate was obtained.

[0063] Example 2

[0064] This embodiment provides a strontium titanate ceramic material and a grain boundary layer ceramic substrate, comprising the following raw materials:

[0065] Table 2 Raw material parameters for Example 2

[0066] Raw material A 99 0.6 0.4 0 0 Raw materials (mol%) <![CDATA[SrTiO3]]> GA-1 GA-4 GA-9 GA-13 Raw material B 96 2 2 0 0

[0067] (1) Prepare raw material A and raw material B.

[0068] According to the above formula, the components of raw material A are mixed and calcined at 1230℃ for 2 hours (heating rate 2℃ / min), then ground and sieved (400 mesh) to obtain raw material A (particle size less than 40μm). The components of raw material B are mixed and calcined at 1200℃ for 2 hours (heating rate 3℃ / min), then ground and sieved (80 mesh) to obtain raw material B (particle size less than 180μm).

[0069] (2) Mix raw material A and raw material B with polyvinyl alcohol and organic solvent, and then mold them to obtain a film.

[0070] The mass ratio of raw material A to raw material B is 4:52, and the mass ratio of the total amount of raw material A and raw material B to the mass of polyvinyl alcohol is 56:5. The organic solvent is xylene and anhydrous ethanol, and the mass ratio of xylene to anhydrous ethanol is 19.5:19.5. The mass ratio of the total amount of raw material A, raw material B, and polyvinyl alcohol to the mass of the organic solvent is 61:39.

[0071] (3) The membrane is subjected to a two-step process of debinding and reduction firing to obtain a semiconductor grain ceramic substrate (thickness 0.2 mm).

[0072] The adhesive removal conditions were: holding at 550℃ for 3 hours, with a heating rate of 3℃ / min. The substrate reduction firing temperature was 1350℃, holding time was 2.5 hours, heating rate was 3℃ / min, and the atmosphere was hydrogen.

[0073] (4) The oxidant dispersion is coated on the surface of the semiconducting grain ceramic substrate to obtain a semiconducting grain ceramic substrate with an oxide medium film attached.

[0074] The oxidant in the oxidant dispersion is a B2O3-Bi2O3 glass material (B2O3 and Bi2O3 in a mass ratio of 1:1), and the solvent is anhydrous ethanol. The mass ratio of the oxidant to the solvent in the oxidant dispersion is 1:1.5. The oxidant and dispersion are uniformly coated on the surface (single-sided) of the strontium titanate ceramic prepared in the previous step, with a thickness of 8 μm.

[0075] (5) Under a pure oxygen atmosphere, the semiconductor grain ceramic substrate with the oxide dielectric film attached is subjected to oxidation heat treatment to form a grain boundary insulating layer, thereby obtaining a grain boundary layer ceramic substrate.

[0076] The flow rate of pure oxygen used in the pure oxygen atmosphere was 3 L / min, the temperature of the oxidation heat treatment was 900℃, the time of the oxidation heat treatment was 3 h, and the heating rate was 4℃ / min. Finally, a grain boundary layer ceramic substrate was obtained.

[0077] Example 3

[0078] This embodiment provides a strontium titanate ceramic material and a grain boundary layer ceramic substrate, comprising the following raw materials:

[0079] Table 3 Raw material parameters for Example 3

[0080] Raw material A 99.1 0 0.4 0.5 0 Raw materials (mol%) <![CDATA[SrTiO3]]> GA-1 GA-4 GA-9 GA-13 Raw material B 98 0 0 0 2

[0081] (1) Prepare raw material A and raw material B.

[0082] According to the above formula, the components of raw material A are mixed and calcined at 1310℃ for 3 hours (heating rate 4℃ / min), then ground and sieved (400 mesh) to obtain raw material A (particle size less than 40μm). The components of raw material B are mixed and calcined at 1250℃ for 3 hours (heating rate 4℃ / min), then ground and sieved (80 mesh) to obtain raw material B (particle size less than 180μm).

[0083] (2) Mix raw material A and raw material B with polyvinyl alcohol and organic solvent, and then mold them to obtain a film.

[0084] The mass ratio of raw material A to raw material B is 5.5:55, and the mass ratio of the total amount of raw material A and raw material B to the mass ratio of polyvinyl alcohol is 60.5:5. The organic solvent is xylene and anhydrous ethanol, and the mass ratio of xylene to anhydrous ethanol is 17.25:17.25. The mass ratio of the total amount of raw material A, raw material B, and polyvinyl alcohol to the mass ratio of the organic solvent is 65.5:34.5.

[0085] (3) The membrane is subjected to a two-step process of debinding and reduction firing to obtain a semiconductor grain ceramic substrate (thickness 0.2 mm).

[0086] The adhesive removal conditions were: holding at 580℃ for 2 hours, with a heating rate of 2℃ / min. The substrate reduction firing temperature was 1375℃, holding time was 2 hours, heating rate was 4℃ / min, and the atmosphere was hydrogen.

[0087] (4) The oxidant dispersion is coated on the surface of the semiconducting grain ceramic substrate to obtain a semiconducting grain ceramic substrate with an oxide medium film attached.

[0088] The oxidant in the oxidant dispersion is a B2O3-Bi2O3 glass material (B2O3 and Bi2O3 in a mass ratio of 1:1), and the solvent in the oxidant dispersion is anhydrous ethanol. The mass ratio of the oxidant to the solvent in the oxidant dispersion is 1:1. The oxidant and dispersion are uniformly coated on the surface (single-sided) of the strontium titanate ceramic prepared in the previous step, with a thickness of 3 μm.

[0089] (5) Under a pure oxygen atmosphere, the semiconductor grain ceramic substrate with the oxide dielectric film attached is subjected to oxidation heat treatment to form a grain boundary insulating layer, thereby obtaining a grain boundary layer ceramic substrate.

[0090] The flow rate of pure oxygen used in the pure oxygen atmosphere was 5 L / min, the temperature of the oxidation heat treatment was 800℃, the time of the oxidation heat treatment was 2.5 h, and the heating rate was 5℃ / min. Finally, a grain boundary layer ceramic substrate was obtained.

[0091] Example 4

[0092] This embodiment provides a strontium titanate ceramic material and a grain boundary layer ceramic substrate, comprising the following raw materials:

[0093] Table 4 Raw material parameters for Example 4

[0094]

[0095]

[0096] (1) Prepare raw material A and raw material B.

[0097] According to the above formula, the components of raw material A are mixed and calcined at 1280℃ for 4 hours (heating rate 5℃ / min), then ground and sieved (400 mesh) to obtain raw material A (particle size less than 40μm). The components of raw material B are mixed and calcined at 1300℃ for 4 hours (heating rate 5℃ / min), then ground and sieved (80 mesh) to obtain raw material B (particle size less than 180μm).

[0098] (2) Mix raw material A and raw material B with polyvinyl alcohol and organic solvent, and then mold them to obtain a film.

[0099] The mass ratio of raw material A to raw material B is 6:50, and the mass ratio of the total amount of raw material A and raw material B to the mass ratio of polyvinyl alcohol is 56:4. The organic solvent is xylene and anhydrous ethanol, and the mass ratio of xylene to anhydrous ethanol is 20:20. The mass ratio of the total amount of raw material A, raw material B, and polyvinyl alcohol to the mass ratio of the organic solvent is 60:40.

[0100] (3) The membrane is subjected to a two-step process of debinding and reduction firing to obtain a semiconductor grain ceramic substrate (thickness 0.2 mm).

[0101] The adhesive removal conditions were: holding at 600℃ for 4 hours, with a heating rate of 3℃ / min. The substrate reduction firing temperature was 1385℃, holding time was 3 hours, heating rate was 3℃ / min, and the atmosphere was hydrogen.

[0102] (4) The oxidant dispersion is coated on the surface of the semiconducting grain ceramic substrate to obtain a semiconducting grain ceramic substrate with an oxide medium film attached.

[0103] The oxidant in the oxidant dispersion is a B2O3-Bi2O3 glass material (B2O3 and Bi2O3 in a mass ratio of 1:1), and the solvent is anhydrous ethanol. The mass ratio of oxidant to solvent in the oxidant dispersion is 1:1.2. The oxidant and dispersion are uniformly coated on the surface (single-sided) of the strontium titanate ceramic prepared in the previous step, with a thickness of 10 μm.

[0104] (5) Under a pure oxygen atmosphere, the semiconductor grain ceramic substrate with the oxide dielectric film attached is subjected to oxidation heat treatment to form a grain boundary insulating layer, thereby obtaining a grain boundary layer ceramic substrate.

[0105] The flow rate of pure oxygen used in the pure oxygen atmosphere was 1 L / min, the temperature of the oxidation heat treatment was 900℃, the time of the oxidation heat treatment was 2 h, and the heating rate was 3.5℃ / min. Finally, a grain boundary layer ceramic substrate was obtained.

[0106] Example 5

[0107] This embodiment provides a strontium titanate ceramic material and a grain boundary layer ceramic substrate, comprising the following raw materials:

[0108] Table 5 Raw material parameters for Example 5

[0109] Raw material A 99.7 0.3 0.5 0.2 0 Raw materials (mol%) <![CDATA[SrTiO3]]> GA-1 GA-4 GA-9 GA-13 Raw material B 93 1 2 2 2

[0110] (1) Prepare raw material A and raw material B.

[0111] According to the above formula, the components of raw material A are mixed and calcined at 1280℃ for 3 hours (heating rate 5℃ / min), then ground and sieved (400 mesh) to obtain raw material A (particle size less than 40μm). The components of raw material B are mixed and calcined at 1280℃ for 3 hours (heating rate 5℃ / min), then ground and sieved (80 mesh) to obtain raw material B (particle size less than 180μm).

[0112] (2) Mix raw material A and raw material B with polyvinyl alcohol and organic solvent, and then mold them to obtain a film.

[0113] The mass ratio of raw material A to raw material B is 5:50, and the mass ratio of the total amount of raw material A and raw material B to the mass ratio of polyvinyl alcohol is 55:5. The organic solvent is xylene and anhydrous ethanol, the mass ratio of xylene to anhydrous ethanol is 20:20, and the mass ratio of the total amount of raw material A, raw material B, and polyvinyl alcohol to the mass ratio of the organic solvent is 60:40.

[0114] (3) The membrane is subjected to a two-step process of debinding and reduction firing to obtain a semiconductor grain ceramic substrate (thickness 0.2 mm).

[0115] The adhesive removal conditions were: holding at 560℃ for 3 hours, with a heating rate of 2.5℃ / min. The substrate reduction firing temperature was 1325℃, holding time was 3 hours, heating rate was 3℃ / min, and the atmosphere was hydrogen.

[0116] (4) The oxidant dispersion is coated on the surface of the semiconducting grain ceramic substrate to obtain a semiconducting grain ceramic substrate with an oxide medium film attached.

[0117] The oxidant in the oxidant dispersion is a B2O3-Bi2O3 glass material (B2O3 and Bi2O3 in a mass ratio of 1:1), and the solvent in the oxidant dispersion is anhydrous ethanol. The mass ratio of the oxidant to the solvent in the oxidant dispersion is 1:1. The oxidant and dispersion are uniformly coated on the surface (single-sided) of the strontium titanate ceramic prepared in the previous step, with a thickness of 5 μm.

[0118] (5) Under a pure oxygen atmosphere, the semiconductor grain ceramic substrate with the oxide dielectric film attached is subjected to oxidation heat treatment to form a grain boundary insulating layer, thereby obtaining a grain boundary layer ceramic substrate.

[0119] The flow rate of pure oxygen used in the pure oxygen atmosphere was 2 L / min, the temperature of the oxidation heat treatment was 1000℃, the time of the oxidation heat treatment was 3 h, and the heating rate was 4.5℃ / min. Finally, a grain boundary layer ceramic substrate was obtained.

[0120] Table 6 Performance data of the grain boundary layer ceramic substrates prepared in Examples 1-5

[0121] K (1MHz) 21522 25816 24116 25250 23684 <![CDATA[Dielectric loss (×10 -4 )]]> 45 59 53 59 51 50V resistor (GΩ) 112 112 106 150 117 K-value difference rate ≤5.1％ ≤5.3％ ≤6.0％ ≤6.37％ ≤4.37％

[0122] The K-value difference rate in the embodiments of the present invention is ≤7%, while that of conventional processes is 15-20%, indicating that the grain boundary layer ceramic material of the present invention has excellent electrical properties. In addition, the obtained ceramic grain size (about 10 μm) is more uniform than that of strontium titanate ceramics produced by conventional processes (about 3 μm), which greatly improves the dielectric properties of the ceramic.

[0123] Comparative Example 1

[0124] Table 7 Raw material parameters for Comparative Example 1

[0125] Raw material C 98 0 0 0 2

[0126] (1) Preparation of raw material C

[0127] According to the above formula, the components of raw material C are mixed and calcined at 1200℃ for 3 hours (heating rate 5℃ / min), and then ground and sieved (80 mesh) to obtain raw material C (particle size less than 180μm).

[0128] (2) Mix raw material C with polyvinyl alcohol and organic solvent, and then mold it to obtain a film.

[0129] The mass ratio of raw material C to polyvinyl alcohol is 55:5. The organic solvent is xylene and anhydrous ethanol, with a mass ratio of xylene to anhydrous ethanol of 20:20. The mass ratio of the total amount of raw material C and polyvinyl alcohol to the mass ratio of the organic solvent is 60:40.

[0130] (3) The diaphragm is subjected to a two-step process of debinding and reduction sintering to obtain a semiconductor grain ceramic substrate (thickness 0.2 mm). Figure 1 ).

[0131] The adhesive removal conditions were: holding at 560℃ for 3 hours, with a heating rate of 2.5℃ / min. The substrate reduction firing temperature was 1325℃, holding time was 3 hours, heating rate was 3℃ / min, and the atmosphere was hydrogen.

[0132] (4) The oxidant dispersion is coated on the surface of the semiconducting grain ceramic substrate to obtain a semiconducting grain ceramic substrate with an oxide medium film attached.

[0133] The oxidant in the oxidant dispersion is a B2O3-Bi2O3 glass material (B2O3 and Bi2O3 in a mass ratio of 1:1), and the solvent in the oxidant dispersion is anhydrous ethanol. The mass ratio of the oxidant to the solvent in the oxidant dispersion is 1:1. The oxidant and dispersion are uniformly coated on the surface (single-sided) of the strontium titanate ceramic prepared in the previous step, with a thickness of 10 μm.

[0134] (5) Under a pure oxygen atmosphere, the semiconductor grain ceramic substrate with the oxide dielectric film attached is subjected to oxidation heat treatment to form a grain boundary insulating layer, thereby obtaining a grain boundary layer ceramic substrate.

[0135] The flow rate of pure oxygen used in the pure oxygen atmosphere was 2 L / min. The temperature of the oxidation heat treatment was 1000℃, the treatment time was 3 h, and the heating rate was 4.5℃ / min. Finally, a grain boundary layer ceramic substrate was obtained. The resulting ceramic grains lacked uniformity, with many grains smaller than 5 μm.

[0136] Table 8 shows the dielectric properties of Comparative Example 1. Compared with the previous example, Comparative Example 1 did not incorporate high-melting-point oxides into its strontium titanate ceramics. Instead, it used SrTiO3 doped with the glass phase to prepare the strontium titanate ceramic capacitor. Due to the uneven grain size, Comparative Example 1 had higher dielectric loss and lower resistance, resulting in a larger difference in K values.

[0137] Table 8 Performance data of the ceramic substrate at the grain boundary layer in Comparative Example 1

[0138] Comparative Example 1 29562 115 3.6 ≤21％

[0139] Comparative Example 2

[0140] Table 9 Raw material parameters for Comparative Example 2

[0141] Raw material D 99.0 0.3 0.5 0.2 0

[0142] (1) Preparation of raw material D.

[0143] According to the above formula, the components of raw material D are mixed and calcined at 1200℃ for 3 hours (heating rate 5℃ / min), and then ground and sieved (400 mesh) to obtain raw material D (particle size less than 40μm).

[0144] (2) Mix raw material D with polyvinyl alcohol and organic solvent, and mold to obtain a film.

[0145] The mass ratio of raw material D to polyvinyl alcohol is 52:5. The organic solvent is xylene and anhydrous ethanol, and the mass ratio of xylene to anhydrous ethanol is 21.5:21.5. The mass ratio of the total amount of raw material D and polyvinyl alcohol to the organic solvent is 57:43.

[0146] (3) The diaphragm is subjected to a two-step process of debinding and reduction sintering to obtain a semiconductor grain ceramic substrate (thickness 0.2 mm). Figure 2 ).

[0147] The adhesive removal conditions were: holding at 600℃ for 4 hours, with a heating rate of 3℃ / min. The substrate reduction firing temperature was 1385℃, holding time was 3 hours, heating rate was 3℃ / min, and the atmosphere was hydrogen.

[0148] (4) The oxidant dispersion is coated on the surface of the semiconducting grain ceramic substrate to obtain a semiconducting grain ceramic substrate with an oxide medium film attached.

[0149] The oxidant in the oxidant dispersion is a B2O3-Bi2O3 glass material (B2O3 to Bi2O3 mass ratio of 1:1), and the solvent in the oxidant dispersion is anhydrous ethanol. The mass ratio of oxidant to solvent in the oxidant dispersion is 1:1.2. The oxidant and dispersion are uniformly coated on the surface (single-sided) of the strontium titanate ceramic prepared in the previous step, with a thickness of 7 μm.

[0150] (5) Under a pure oxygen atmosphere, the semiconductor grain ceramic substrate with the oxide dielectric film attached is subjected to oxidation heat treatment to form a grain boundary insulating layer, thereby obtaining a grain boundary layer ceramic substrate.

[0151] The flow rate of pure oxygen used in the pure oxygen atmosphere was 1 L / min, the temperature of the oxidation heat treatment was 900℃, the time of the oxidation heat treatment was 2 h, and the heating rate was 3.5℃ / min. Finally, a grain boundary layer ceramic substrate was obtained.

[0152] In this comparative example, STO ceramics were prepared by pre-firing glass powder and oxide simultaneously, eliminating the need for preparing raw materials A and B. However, the resulting ceramic still exhibited uneven grain distribution. Table 10 shows the performance data of the ceramic substrate in Comparative Example 2.

[0153] Table 10 Performance data of the grain boundary layer ceramic substrate in Comparative Example 2

[0154] Comparative Example 1 22341 91 12 ≤16％

[0155] The dielectric loss is relatively high, the resistance is relatively low, and the K value difference rate is also relatively high due to the uneven grain distribution and small average grain size.

[0156] Comparative Example 3

[0157] (1) Mix pure strontium titanate with polyvinyl alcohol and organic solvent, and then mold to obtain a film.

[0158] The mass ratio of pure strontium titanate to polyvinyl alcohol is 55:5. The organic solvent is xylene and anhydrous ethanol, with a mass ratio of xylene to anhydrous ethanol of 20:20. The total mass ratio of strontium titanate and polyvinyl alcohol to the organic solvent is 60:40.

[0159] (2) The diaphragm is subjected to a two-step process of debinding and reduction sintering to obtain a semiconductor grain ceramic substrate (thickness 0.2 mm). Figure 3 ).

[0160] The adhesive removal conditions were: holding at 650℃ for 4 hours, with a heating rate of 2℃ / min. The substrate reduction firing temperature was 1400℃, holding time was 2.5 hours, heating rate was 2℃ / min, and the atmosphere was hydrogen.

[0161] (3) The oxidant dispersion is coated on the surface of the semiconducting grain ceramic substrate to obtain a semiconducting grain ceramic substrate with an oxide medium film attached.

[0162] The oxidant in the oxidant dispersion is a B2O3-Bi2O3 glass material (B2O3 and Bi2O3 in a mass ratio of 1:1), and the solvent in the oxidant dispersion is anhydrous ethanol. The mass ratio of the oxidant to the solvent in the oxidant dispersion is 1:1. The oxidant and dispersion are uniformly coated on the surface (single-sided) of the strontium titanate ceramic prepared in the previous step, with a thickness of 10 μm.

[0163] (4) Under a pure oxygen atmosphere, the semiconductor grain ceramic substrate with the oxide dielectric film attached is subjected to oxidation heat treatment to form a grain boundary insulating layer, thereby obtaining a grain boundary layer ceramic substrate.

[0164] The flow rate of pure oxygen used in the pure oxygen atmosphere was 3 L / min, the temperature of the oxidation heat treatment was 1000℃, the time of the oxidation heat treatment was 1 h, and the heating rate was 3℃ / min. Finally, a grain boundary layer ceramic substrate was obtained.

[0165] This comparative example uses pure SrTiO3 to prepare STO ceramics, eliminating the need for the preparation of raw materials A and B. However, the resulting ceramic grains are smaller, with an average particle size of 1 μm. Table 11 shows the performance data of the ceramic substrate in Comparative Example 2.

[0166] Table 11

[0167] Comparative Example 1 2480 207 125 ≤7％

[0168] As can be seen, without the addition of a glass phase, the dielectric constant K is lower due to the smaller grain size, resulting in higher losses.

[0169] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a strontium titanate ceramic material, characterized in that, Includes the following steps: (1) SrTiO3 powder and dopant are mixed, sintered, ground and sieved to obtain raw material A; the dopant is one or more of Nb2O5 powder, La2O3 powder, MgO powder and Nd2O3 powder; the molar ratio of the dopant to SrTiO3 is (0.2~1):(99~99.8); the sintering temperature is 1200℃~1350℃; (2) Mix SrTiO3 powder and glass powder, calcine, grind and sieve to obtain raw material B; the glass powder is one or more of GA-13, GA-1, GA-4 and GA-9 glass materials produced by Asahi Glass Co., Ltd.; the molar ratio of the glass powder to SrTiO3 is (0.6~7):(93~99.4); the calcination temperature is 1200℃~1350℃; (3) Mix raw material A, raw material B, adhesive and organic solvent, and mold to obtain a film; the mass ratio of raw material A to raw material B is (0.5~7.5):(50~60); (4) The membrane is debonded and reduced and sintered to obtain strontium titanate ceramic material; the reduction and sintering temperature is 1300℃~1400℃ and the atmosphere is hydrogen atmosphere.

2. The strontium titanate ceramic material prepared by the preparation method according to claim 1.

3. A method for preparing a ceramic substrate with a grain boundary layer, characterized in that, Includes the following steps: (a) The oxidant dispersion is coated onto the surface of the strontium titanate ceramic material according to claim 2 to obtain a strontium titanate ceramic material with an oxide medium film attached. (b) Under an oxygen atmosphere, the strontium titanate ceramic material with the oxide medium film attached is subjected to an oxidative heat treatment to obtain a grain boundary layer ceramic substrate.

4. The preparation method according to claim 3, characterized in that, In step (a), the oxidant in the oxidant dispersion is B2O3-Bi2O3 glass, the mass ratio of B2O3 to Bi2O3 is 1:1~1.5, the solvent of the oxidant dispersion is one or more of terpineol, anhydrous ethanol and n-butanol; the mass ratio of the oxidant to the solvent in the oxidant dispersion is 1:(1~2); the coating thickness of the oxidant dispersion is 1~10μm.

5. The preparation method according to claim 3, characterized in that, The oxygen atmosphere in step (b) is a pure oxygen atmosphere; the flow rate of the oxygen atmosphere is (1~5) L / min; the temperature of the oxidation heat treatment is 800~1000℃, the time of the oxidation heat treatment is 1~3h, and the heating rate is 3~5℃ / min.

6. A grain boundary layer ceramic substrate prepared by the preparation method according to any one of claims 3-5.

7. The application of the strontium titanate ceramic material of claim 2 and the grain boundary layer ceramic substrate of claim 6 in the preparation of chip capacitors.

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