Wide-temperature stable high-dielectric low-loss ceramic capacitor dielectric material and preparation method and application thereof

Abstract

The invention belongs to a ceramic capacitor dielectric material, and particularly relates to a wide-temperature-range stable high-dielectric low-loss ceramic capacitor dielectric material and a preparation method and application thereof. The nominal chemical composition of the ceramic capacitor dielectric material is (Bi < 0.47 > Na < 0.47 > Ba < 0.06 >) < 1-x > Sr < x > Ti < 1-x > Fe < x > / 2 > Nb < x > / 2O3, wherein x is 0.10-0.18. The ceramic capacitor dielectric material is prepared by adopting Bi2O3, BaCO3, SrCO3, TiO2, Fe2O3, Nb2O5 and Na2CO3 as raw materials, is of a pure perovskite structure and has tetragonal phase and trigonal phase characteristic peaks, and a nano domain structure exists in ceramic crystal grains. The ceramic capacitor dielectric material has the advantages of wide temperature range stability, high dielectric constant, low dielectric loss and the like, and is suitable for preparing ceramic capacitors under high-temperature working conditions.

Description

Technical Field

[0001] The present invention belongs to the dielectric materials of ceramic capacitors, and particularly relates to a dielectric material for a wide-temperature stable high-dielectric-constant and low-loss ceramic capacitor, its manufacturing method and application. Background Art

[0002] As an important type of charge storage component, capacitors can effectively achieve various functions such as filtering, bypassing, coupling, decoupling, pulse discharging, DC blocking, and power regulation in electronic systems. Ceramic capacitors are capacitors with ceramic materials as dielectrics. They have a wide variety of types and significant differences in external dimensions. According to temperature coefficients and different dielectric constants, they can be divided into negative temperature coefficient, positive temperature coefficient, zero temperature coefficient, high dielectric constant, low dielectric constant, etc. In addition, there are classification methods of type I, type II, and type III. Among them, multilayer ceramic capacitors (MLCCs) are widely used in fields such as automotive electronics, consumer electronics, aerospace, and weaponry due to their high capacitance, small size, and good frequency, temperature, and withstand voltage characteristics. China is the country with the largest demand for MLCCs globally, accounting for more than 40% of the global demand; however, restricted by technical levels, the self-supply rate of domestic MLCCs is less than 10%. With the miniaturization, integration of electronic terminal products, and diversification of service environments, large capacitance, small size, resistance to high and low temperatures, high voltage, and high reliability are the main development trends of high-end MLCCs. This poses higher requirements for the dielectric properties of the key ceramic dielectric materials, which need to have a stable dielectric constant within a very wide temperature range. At the same time, to meet the requirements of large capacitance, high voltage resistance, and high reliability of capacitors, the ceramic dielectric materials should also have high dielectric constant and low dielectric loss.

[0003] The main ceramic material for commercial high-capacitance MLCCs is barium titanate (BaTiO 3 ), and the room-temperature dielectric constant of the commercial BaTiO 3 system is ε r ~2000, and the Curie temperature is T C ~120 °C. Such dielectric-temperature characteristics are difficult to meet the temperature stability requirements, and the temperature stability can be improved by modifying and constructing a "core-shell" structure, broadening the Curie peak, or moving the Curie temperature out of the working temperature range. However, currently, the working temperature of the commercially available X7R type MLCC on the market is -55 to 125 °C (room temperature ε r : 2000 - 3000, capacitance-temperature change rate ΔC / C 25 ℃ ≤ ±15%), and the advanced X9R type MLCC has a working temperature of -55 to 200 °C (room temperature ε r : 1000 - 1500). Limited by BaTiO3 With a relatively low Curie temperature and a sharp dielectric peak, it is difficult to break through the limits of higher and lower operating temperatures. Once outside the operating temperature range, the capacitance of MLCC devices decreases and the loss increases, and the temperature stability, withstand voltage characteristics, and reliability are all significantly reduced. Patent documents with application numbers CN200710048476.2 (CN101033132A), CN202210715016.5 (publication number CN115159977A), and CN202410373599.7 (publication number CN118530018A) have all disclosed ceramic capacitor dielectric materials based on BaTiO 3 , although the dielectric constant ε r is relatively high, but the high-temperature stability is poor and it cannot break through the 200 °C operating temperature range. The patent document with application number CN201910430453.0 (publication number CN110128132A) has disclosed a dielectric material for ultra-wide temperature multi-layer lead-free ceramic capacitors based on CaZrO 3 , with improved wide-temperature stability, but the dielectric constant is relatively low and does not exceed 840.

[0004] In some scenarios, electronic systems will face extreme high-temperature working conditions. For example, the aviation aircraft control system monitors the engine combustion state in real time. Related electronic devices need to be as close to the engine as possible and may need to withstand temperatures as high as 200–500 °C. The working temperatures of electronic devices in fields such as automotive electronics, oil drilling, SOI, or WBG semiconductor devices may also exceed 200 °C. Therefore, it is crucial to develop wide-temperature stable ceramic capacitors that can work in extreme high-temperature environments. Therefore, there is an urgent need to seek a new type of high-dielectric-constant and low-loss ceramic dielectric material system with wide-temperature stability and conduct performance optimization research to meet the application of ceramic capacitors in extreme environments. Summary of the Invention

[0005] In view of the above problems, the present invention provides a wide-temperature stable, high-dielectric-constant, and low-dielectric-loss ceramic capacitor dielectric material, its preparation method, and application. Specifically, it provides a wide-temperature stable, high-dielectric-constant, and low-dielectric-loss ceramic capacitor dielectric material, as well as the preparation method and application of this ceramic capacitor dielectric material.

[0006] First of all, the present invention provides a wide-temperature stable, high-dielectric-constant, and low-dielectric-loss ceramic capacitor dielectric material. The nominal chemical composition of the ceramic capacitor dielectric material is (Bi 0.47 Na 0.47 Ba 0.06 ) 1-x Sr x Ti 1-x Fe x / 2 Nb x / 2 O 3 , where xIt is 0.10 to 0.18.

[0007] The dielectric material of the ceramic capacitor uses Bi 2 O 3 , BaCO 3 , SrCO 3 , TiO 2 , Fe 2 O 3 , Nb 2 O 5 and Na 2 CO 3 as raw materials.

[0008] The X-ray diffraction pattern of the dielectric material of the ceramic capacitor shows a pure perovskite structure, with tetragonal and rhombohedral characteristic peaks; there is a nano-domain structure in the ceramic grains of the dielectric material of the ceramic capacitor.

[0009] Preferably, the x is 0.10 to 0.15; more preferably, the x is 0.12.

[0010] The relative dielectric constant of this ceramic capacitor dielectric material is maintained at 2500 to 3000 in the temperature range of 50 to 300 °C, the temperature coefficient of capacitance in the temperature range of 50 to 300 °C is less than 15%, and the dielectric loss in the temperature range of 80 to 300 °C is less than 0.02. It is a high-dielectric-constant and low-loss ceramic capacitor dielectric material with wide-temperature stability, suitable for preparing high-temperature-resistant ceramic capacitors.

[0011] Secondly, the present invention provides a preparation method for the foregoing dielectric material of the ceramic capacitor, including the following steps: S1 Na 2 CO 3 pretreatment: Na 2 CO 3 powder is dried at 200 °C for 3 h on a temperature-controlled magnetic stirrer as Na 2 CO 3 material; S2 Batching and first grinding: Batching is carried out according to the nominal chemical composition, and Bi 2 O 3 , BaCO 3 , SrCO 3 , TiO 2 , Fe 2 O 3 , Nb 2 O 5 and the Na 2 CO 3The raw materials are used as raw materials; the raw materials are put into a ball milling jar, zirconium oxide balls and anhydrous ethanol are used as ball milling media, and the raw materials are put into a planetary ball mill. After ball milling, the raw materials are dried and passed through a 150-mesh sieve to obtain a mixed material A; the mixed material A is heated to 850°C at a heating rate of 5°C / min in an air atmosphere, kept at this temperature for 5 hours, and then cooled with the furnace to obtain a pre-sintered powder; S3 Second grinding: the calcined powder obtained in step S2, anhydrous ethanol and zirconium oxide are poured into a ball milling jar, placed in a planetary ball mill, ball milled, dried and sieved through a 200-mesh sieve to obtain a mixed material B; S4 granulation and sintering: Add 3% polyvinyl butyral by mass to the mixed material B, grind it thoroughly until the powder is granular, and obtain granulated powder with uniform particles; take the granulated powder and press it into a cylindrical green body with a diameter of about 10mm under a pressure of 20Mpa for 5 minutes; place the green body in a crucible, bury it with pre-burned powder of the same composition, first heat it up to 500℃ at a rate of 1℃ / min for 3 hours to remove the binder, then heat it up to 1200℃ at a rate of 5℃ / min for 3 hours, and naturally cool it with the furnace to obtain ceramic materials. In addition to the cylindrical green body with a diameter of about 10mm, there are many choices in the shape or specification of the ceramic green body in this field, such as 8mm cylindrical green body, rectangular green body, etc.

[0012] Preferably, in step S2, the mass ratio of the raw material, anhydrous ethanol and zirconium oxide balls is 1:1:3.

[0013] Preferably, in step S2, the preparation conditions of the mixed material A are: ball milling at a rotation speed of 250 rpm for 18 hours, and then drying at 70° C. for 24 hours.

[0014] Preferably, in step S3, the mass ratio of the calcined powder, anhydrous ethanol and zirconium oxide is 15:20:45.

[0015] Preferably, in step S3, the preparation conditions of the mixed material B are: ball milling at a speed of 400 rpm for 12 hours, and then drying at 70° C. for 24 hours.

[0016] Finally, the present invention provides the use of the aforementioned ceramic capacitor dielectric material in the preparation of ceramic capacitors, especially in the preparation of ceramic capacitors for high temperature working conditions, for example, in the preparation of ceramic capacitors for aircraft control systems that monitor the engine combustion status in real time.

[0017] The ceramic capacitor dielectric material provided by the present invention does not contain Sr 2+ , Fe 3+ , Nb 5+ When the nominal chemical composition is Bi 0.47 Na 0.47 Ba 0.06 TiO 3 When Sr is added, the temperature stability of the dielectric constant is poor. 2+, Fe 3+ , Nb 5+ After that, Bi 3+ , Na + , Ba 2+ and Sr 2+ ions coexist in the A-site of the perovskite structure; Ti 4+ , Fe 3+ and Nb 5+ ions coexist in the B-site; Whether in the A-site or the B-site, cations with multiple valence states and different ionic radii coexist, resulting in a significant enhancement of the random field in the material, the long-range ferroelectric ordered structure is destroyed, a nano-domain structure appears, and the decrease in the size of the polar region and the reduction in the coupling degree significantly enhance the dielectric relaxation of the ceramic, which is reflected in the dielectric temperature spectrum as the broadening and depression of the dielectric peak. When x is 0.10 - 0.15, a high and flat dielectric constant platform is formed, and the high-temperature end of the metastable interval is extended to 300 °C.

[0018] The research finds that for the dielectric material of the ceramic capacitor of the present invention, the contents of Sr 2+ , Fe 3+ , Nb 5+ have an important influence on the dielectric constant, dielectric loss and their temperature stability of the dielectric material. When controlling x to be 0.10 - 0.15, it can unexpectedly exhibit excellent dielectric properties. Below the lower limit mentioned above, the dielectric constant at the low-temperature end decreases significantly while the dielectric loss is high, and the temperature stability of the dielectric properties is poor; while above the upper limit mentioned above, the dielectric constant at the high-temperature end decreases significantly while the dielectric loss is high, and the temperature stability of the dielectric properties is also poor.

[0019] Advantages of the present invention: The present invention provides a dielectric material for ceramic capacitors with excellent dielectric properties and temperature stability. Its relative dielectric constant is maintained at 2500 - 3000 in the temperature range of 50 - 300 °C, the temperature coefficient of capacitance is less than 15% in the temperature range of 50 - 300 °C, and the dielectric loss is less than 0.02 in the temperature range of 80 - 300 °C. It is a high-dielectric-constant and low-loss ceramic capacitor dielectric material with wide-temperature stability. Its high-temperature dielectric properties and temperature stability are significantly superior to commercial barium titanate-based dielectric ceramic materials, and it is suitable for use as a capacitor under high-temperature working conditions, such as a ceramic capacitor with a working temperature of 50 - 300 °C. Description of the drawings

[0020] Figure 1 is the XRD pattern and nano-domain structure of the ceramic in Example 1; Figure 2 is the dielectric temperature spectrum of the ceramic in Example 1 and the curve of the temperature coefficient of capacitance varying with temperature at 1 kHz; Figure 3Variation curve of DC resistivity of the ceramic in Example 1 with temperature; Figure 4 XRD pattern of the ceramic in Example 2; Figure 5 Dielectric temperature spectrum of the ceramic in Example 2 and variation curve of capacitance-temperature change rate with temperature at 1 kHz; Figure 6 XRD pattern of the ceramic in Example 3; Figure 7 Dielectric temperature spectrum of the ceramic in Example 3 and variation curve of capacitance-temperature change rate with temperature at 1 kHz; Figure 8 XRD pattern of the ceramic in Comparative Example 1; Figure 9 Dielectric temperature spectrum of the ceramic in Comparative Example 1 and variation curve of capacitance-temperature change rate with temperature at 1 kHz; Figure 10 XRD pattern of the ceramic in Comparative Example 2; Figure 11 Dielectric temperature spectrum of the ceramic in Comparative Example 2 and variation curve of capacitance-temperature change rate with temperature at 1 kHz. Detailed implementation manners

[0021] The following uses specific examples to illustrate the solutions and effects of the present invention. The examples are only used for the illustration and display of the present invention, rather than limiting the protection scope of the present invention. The present invention provides a ceramic capacitor dielectric material with a nominal chemical composition of (Bi 0.47 Na 0.47 Ba 0.06 ) 1-x Sr x Ti 1-x Fe x / 2 Nb x / 2 O 3 and its preparation method, and demonstrates its performance characteristics, where x is 0.10 - 0.15.

[0022] Example 1 A high-dielectric and low-loss ceramic capacitor dielectric material with wide-temperature stability and its preparation method This example provides a high-dielectric and low-loss ceramic capacitor dielectric material with a nominal chemical composition of Bi 0.4136 Na 0.4136 Ba 0.0528 Sr 0.12 Ti 0.88 Fe 0.06 Nb 0.06 O 3 , that is, x = 0.12 and its preparation method.

[0023] Preparation of the high-dielectric and low-loss ceramic capacitor dielectric material: (1)Na 2 CO 3 The powder was dried at 200 °C for 3 h on a temperature-controlled magnetic stirrer as Na 2 CO 3 materials; (2) According to the nominal chemical composition Bi 0.4136 Na 0.4136 Ba 0.0528 Sr 0.12 Ti 0.88 Fe 0.06 Nb 0.06 O 3 The ingredients were prepared by weighing Bi and 2 O 3 、BaCO 3 、SrCO 3 、TiO 2 , Fe 2 O 3 , Nb 2 O 5 and Na prepared in step (1) 2 CO 3 The material is used as raw material; the raw material is put into a ball mill, and zirconium oxide balls and anhydrous ethanol are used as ball milling media. The mass ratio of raw material, anhydrous ethanol and zirconium oxide balls is 1:1:3, and the raw material is put into a planetary ball mill, and the ball mill is at 250rpm for 18h. The ball mill is taken out, dried at 70℃ for 24h, and passed through a 150-mesh sieve to obtain a mixed material A. The mixed material A is heated to 850℃ at a heating rate of 5℃ / min in an air atmosphere, and the pre-burned powder is obtained after being kept warm for 5h. The pre-burned powder, anhydrous ethanol and zirconium oxide balls are taken at a mass ratio of 15:20:45, poured into a ball mill, put into a planetary ball mill, ball milled at 400rpm for 12h, and then dried at 70℃ for 24h, and passed through a 200-mesh sieve to obtain a mixed material B. 3% of polyvinyl butyral by mass is added to the mixed material B, and the powder is fully ground until it is granular to obtain a granulated powder with uniform particles. Take 0.3g of granulated powder and press it into a cylindrical green body with a diameter of about 10mm under a pressure of 20Mpa for 5 minutes. Place the green body in an alumina crucible and calcine it with pre-burned powder of the same composition. First, heat it up to 500℃ at a rate of 1℃ / min and keep it for 3 hours to remove the binder. Then heat it up to 1200℃ at a rate of 5℃ / min and keep it for 3 hours to sinter. Cool it naturally in the furnace to obtain Bi 0.4136 Na 0.4136 Ba 0.0528 Sr 0.12 Ti 0.88 Fe 0.06 Nb 0.06 O 3 Ceramic material.

[0024] Structural Characterization of Ceramic Materials: The crystal phase structure of ceramic materials was analyzed by X-ray diffraction (XRD). As shown in Figure 1 (a), it can be seen that the prepared ceramic material has a pure perovskite structure without impurity phases, proving that Sr 2+ , Fe 3+ , Nb 5+ have been solid-soluted into Bi 0.47 Na 0.47 Ba 0.06 TiO 3 . There are (131) R and (312) R peaks on the XRD pattern, which are characteristic peaks of the rhombohedral phase. At the same time, there is a (002) T peak, which is a characteristic peak of the tetragonal phase. The results of phase structure analysis prove the coexistence of the tetragonal phase and the rhombohedral phase in the ceramic material. The obtained ceramic material was tested by transmission electron microscopy (TEM). As shown in Figure 1 (b), it can be seen that there are randomly dispersed nano-domain structures in the ceramic grains. The nano-domain structure is a regional structure formed on the nano-scale. These structures play a key role in ferroelectric materials and can enhance the polarization intensity of the material through highly localized strong polar states, thereby affecting the energy storage density and efficiency of the material.

[0025] Electrical Property Characterization of Ceramic Materials: The sintered ceramic was polished to a thickness of 0.5 mm, and medium-temperature silver paste was coated on both sides. It was fired at 550 °C for 30 min to form silver electrodes for electrical property testing. The dielectric temperature spectrum was tested using a high-temperature impedance analyzer to measure the curves of the dielectric constant ε r and dielectric loss tan δ as functions of temperature and frequency. In this test, the test temperature range was 25 - 400 °C, and the test frequencies included 1 kHz, 10 kHz, and 100 kHz. Then, the capacitance-temperature change rate Δ C / C 150°C (capacitance at a certain temperature - capacitance at 150 °C) / capacitance at 150 °C) as a function of temperature was calculated using the measured dielectric temperature spectrum to evaluate the temperature stability of the ceramic dielectric capacitance.

[0026] Figure 2 show the dielectric temperature spectrum of the ceramic and the capacitance-temperature change rate Δ C / C 150°CAs the temperature changes, the dielectric temperature spectrum exhibits obvious broadening of the dielectric peak and frequency dispersion phenomena, demonstrating the existence of a diffuse phase transition with temperature in the ceramic. The standard room temperature dielectric constant at 1 kHz is 1955, the dielectric constant at 150 °C is as high as 2820, the dielectric loss is as low as 0.0095, and the temperature coefficient of capacitance Δ C / C 150°C is less than 15% in the temperature range of 50 - 300 °C, and the dielectric loss is less than 0.02 in the temperature range of 80 - 300 °C.

[0027] The temperature-dependent curve of the DC resistivity of the ceramic was obtained using a DC resistance tester. In this test, the temperature range was 25 - 400 °C. It can be seen that the room temperature resistivity is as high as 10 13 Ω•cm, and the resistivity is higher than 10 9 Ω•cm until 300 °C, demonstrating the excellent insulation performance of the ceramic.

[0028] Example 2 A dielectric material for a high-dielectric-constant and low-loss ceramic capacitor with wide-temperature stability and its preparation method Compared with Example 1, the only difference is that x = 0.10, that is, the nominal chemical composition is Bi 0.423 Na 0.4136 Ba 0.054 Sr 0.10 Ti 0.90 Fe 0.05 Nb 0.05 O 3 (The preparation method is the same as that in Example 1, and the performance measurement methods such as electrical property characterization are the same as those in Example 1).

[0029] The XRD pattern of the ceramic material, the dielectric temperature spectrum, and the temperature-dependent curve of the capacitance temperature coefficient at 1 kHz are shown in Figure 4 、 5 .

[0030] From the XRD results, it can be seen that the ceramic material prepared in this example is still a pure perovskite structure without the presence of impurity phases. In the ceramic, the rhombohedral phase and the tetragonal phase still coexist, but the lattice distortions of the rhombohedral and tetragonal phases are slightly higher than those of the ceramic material in Example 1.

[0031] From the dielectric temperature spectrum and the capacitance temperature coefficient curve, it can be seen that the standard room temperature dielectric constant of the ceramic material prepared in this example at 1 kHz is 2005, the dielectric constant at 150 °C is as high as 2820, the dielectric loss is 0.012, and the temperature coefficient of capacitance Δ C / C 150°C is less than 15% in the temperature range of 50 - 300 °C, and the dielectric loss is less than 0.02 in the temperature range of 90 - 320 °C.

[0032] Example 3 A dielectric material for a high-k and low-loss ceramic capacitor with wide-temperature stability and its preparation method Compared with Example 1, the difference is only that x = 0.15, that is, the nominal chemical composition is Bi 0.3995 Na 0.3995 Ba 0.051 Sr 0.1 5 Ti 0.85 Fe 0.075 Nb 0.075 O 3 (The preparation method is the same as that in Example 1, and the performance measurement methods such as electrical property characterization are the same as those in Example 1).

[0033] The XRD pattern, dielectric temperature spectrum, and the curve of capacitance-temperature change rate at 1 kHz as a function of temperature of this ceramic material are shown in Figure 6 、 7 .

[0034] It can be seen from the XRD results that the ceramic material prepared in this example is still a pure perovskite structure without the presence of impurity phases. In the ceramic, the rhombohedral phase and the tetragonal phase still coexist, but the lattice distortions of the rhombohedral and tetragonal phases are slightly lower than those of the ceramic material in Example 1. From the dielectric temperature spectrum and the capacitance-temperature change rate curve, it can be known that the standard room-temperature dielectric constant of this ceramic at 1 kHz is 1940, the dielectric constant at 150 °C is as high as 2615, the dielectric loss is as low as 0.008, and the capacitance-temperature change rate Δ C / C 150°C is less than 15% in the temperature range of 50 - 300 °C, and the dielectric loss is less than 0.02 in the temperature range of 75 - 290 °C.

[0035] Comparative Example 1 A dielectric material for a ceramic capacitor and its preparation method Compared with Example 1, the difference is that the nominal chemical composition is Bi 0.47 Na 0.47 Ba 0.06 TiO 3 , and the preparation method of this dielectric material for a ceramic capacitor is as follows: According to the nominal chemical composition Bi 0.47 Na 0.47 Ba 0.06 TiO 3 for batching, weigh the raw materials of Bi 2 O 3 , Na 2 CO 3 , BaCO 3 and TiO 2 respectively according to the molar ratio. The Na 2 CO 3The powder was dried at 200 °C for 3 h on a temperature-controlled magnetic stirrer before use. All the prepared raw materials were put into a ball milling jar, with zirconia balls and absolute ethanol as the ball milling media. The mass ratio of the raw materials, absolute ethanol and zirconia balls was 1:1:3. It was put into a planetary ball mill and ball milled at 250 rpm for 18 h. The ball milling jar was taken out, dried at 70 °C for 24 h, and sieved through a 150-mesh sieve to obtain the mixed material A. It was heated to 850 °C at a heating rate of 5 °C / min in an air atmosphere, held for 5 h and then cooled with the furnace to obtain the pre-sintered powder. The pre-sintered powder, absolute ethanol and zirconia balls were poured into the ball milling jar in a ratio of 15:20:45, put into a planetary ball mill, ball milled at 400 rpm for 12 h, then dried at 70 °C for 24 h, and sieved through a 200-mesh sieve to obtain the mixed material B. 3% by mass of polyvinyl butyral was added to the mixed material B and ground thoroughly until the powder was granular to obtain the granulated powder with uniform particles. 0.3 g of the granulated powder was taken and pressed into a cylindrical green body with a diameter of about 10 mm under a pressure of 20 Mpa for 5 min. The above green body was placed in an alumina crucible and buried and fired with the pre-sintered powder of the same components. First, it was heated to 500 °C at a heating rate of 1 °C / min and held for 3 h to remove the binder, then heated to 1200 °C at a heating rate of 5 °C / min and held for 3 h for sintering, and cooled naturally with the furnace to prepare the Bi 0.47 Na 0.47 Ba 0.06 TiO 3 ceramic material.

[0036] The crystal phase structure was analyzed by XRD, and the dielectric temperature spectrum was tested by a high-temperature impedance analyzer (the methods for measuring other properties such as electrical property characterization were the same as those in Example 1). The XRD pattern, dielectric temperature spectrum and the curve of capacitance-temperature change rate at 1 kHz of this ceramic material are shown in Figure 8 、 9 respectively.

[0037] It can be seen from the XRD results that the prepared ceramic material is still a pure perovskite structure without the presence of impurity phases. The rhombohedral phase and tetragonal phase still coexist in the ceramic, but the lattice distortions of the rhombohedral and tetragonal phases are significantly higher than those of the ceramic material in Example 1.

[0038] It can be seen from the dielectric temperature spectrum and the capacitance-temperature change rate curve that the standard room temperature dielectric constant of this ceramic at 1 kHz is 1535, the dielectric constant at 150 °C is 4233, the dielectric loss is as high as 0.034, the temperature range with a capacitance-temperature change rate less than 15% is only 120 - 203 °C, and the temperature range with a dielectric loss lower than 0.02 is 155 - 350 °C.

[0039] Comparative Example 2 A dielectric material for ceramic capacitors and its preparation method Compared with Example 1, the only difference is that x = 0.20, that is, the nominal chemical composition is Bi 0.376 Na0.376 Ba 0.048 Sr 0.20 Ti 0.80 Fe 0.10 Nb 0.10 O 3 (The preparation method is the same as that of Example 1, and the performance measurement methods such as electrical property characterization are the same as those of Example 1).

[0040] The XRD pattern, dielectric temperature spectrum, and the curve of the capacitance-temperature change rate at 1 kHz as a function of temperature of this ceramic material are shown in Figure 10 and 11 .

[0041] It can be seen from the XRD results that the prepared ceramic material is still a pure perovskite structure without the presence of impurity phases. In the ceramic, the rhombohedral phase and the tetragonal phase still coexist, but the lattice distortions of the rhombohedral and tetragonal phases are significantly lower than those of the ceramic material in Example 1.

[0042] It can be seen from the dielectric temperature spectrum and the capacitance-temperature change rate curve that the standard room temperature dielectric constant of this ceramic at 1 kHz is 1640, the dielectric constant at 150 °C is 2048, the dielectric loss is 0.0086, the temperature range with a capacitance-temperature change rate of less than 15% is only 25 - 250 °C, and the temperature range with a dielectric loss lower than 0.02 is 50 - 300 °C.

Claims

1. A wide temperature stable high dielectric low loss ceramic capacitor dielectric material, characterized in that: The nominal chemical composition of the ceramic capacitor dielectric material is (Bi 0.47 Na 0.47 Ba 0.06 ) 1-x Sr x Ti 1-x Fe x / 2 Nb x / 2 O3, where x It is 0.10~0.

18.

2. The ceramic capacitor dielectric material according to claim 1, characterized in that: The ceramic capacitor dielectric material is made of Bi2O3, BaCO3, SrCO3, TiO2, Fe2O3, Nb2O5 and Na2CO3 as raw materials.

3. The ceramic capacitor dielectric material according to claim 1, characterized in that: The X-ray diffraction spectrum of the ceramic capacitor dielectric material shows a pure perovskite structure with characteristic peaks of tetragonal phase and rhombohedral phase; and nano-domain structures exist in the ceramic grains of the ceramic capacitor dielectric material.

4. The ceramic capacitor dielectric material according to claim 1, characterized in that Said x It is 0.10~0.

15.

5. A method for preparing a ceramic capacitor dielectric material according to claim 1, characterized in that: The steps include: S1 Na2CO3 pretreatment: Na2CO3 powder was dried at 200℃ for 3h as Na2CO3 material; S2. Batching, first grinding: batching according to the nominal chemical composition, weighing Bi2O3, BaCO3, SrCO3, TiO2, Fe2O3, Nb2O5 and the Na2CO3 material prepared in step S1 as raw materials according to the chemical molar ratio of the metal atoms in the nominal chemical composition expression; putting the raw materials into a ball mill, using zirconium oxide balls and anhydrous ethanol as ball milling media, putting them into a planetary ball mill, drying after ball milling, and sieving with a 150-mesh sieve to obtain a mixed material A; heating the mixed material A to 850°C at a heating rate of 5°C / min in an air atmosphere, keeping the temperature for 5 hours, and then cooling with the furnace to obtain a pre-sintered powder; S3 Second grinding: the calcined powder obtained in step S2, anhydrous ethanol and zirconium oxide are poured into a ball milling jar, placed in a planetary ball mill, ball milled, dried and sieved through a 200-mesh sieve to obtain a mixed material B; S4 granulation and sintering: Add 3% by mass of polyvinyl butyral to the mixed material B, grind it thoroughly until the powder is granular to obtain granulated powder; take the granulated powder and press it into a green body at a pressure of 20Mpa for 5 minutes; place the green body in a crucible and bury it with pre-burned powder of the same composition, first increase the temperature at a rate of 1℃ / min to 500℃ and keep it for 3 hours to debind, then increase the temperature at a rate of 5℃ / min to 1200℃ and keep it for 3 hours to sinter, and cool it naturally in the furnace to obtain a ceramic material.

6. The method for preparing a ceramic capacitor dielectric material according to claim 5, characterized in that: In step S2, the mass ratio of the raw material, anhydrous ethanol and zirconium oxide balls is 1:1:

3.

7. The method for preparing a ceramic capacitor dielectric material according to claim 5, characterized in that: In step S2, the preparation conditions of the mixed material A are: ball milling at a rotation speed of 250 rpm for 18 hours, and then drying at 70° C. for 24 hours.

8. The method for preparing a ceramic capacitor dielectric material according to claim 5, characterized in that: In step S3, the mass ratio of the pre-calcined powder, anhydrous ethanol and zirconium oxide is 15:20:

45.

9. The method for preparing a ceramic capacitor dielectric material according to claim 5, characterized in that: In step S3, the preparation conditions of the mixed material B are: ball milling at a speed of 400 rpm for 12 hours, and then drying at 70° C. for 24 hours.

10. Use of the ceramic capacitor dielectric material according to any one of claims 1 to 4 or the ceramic capacitor dielectric material prepared by the preparation method according to any one of claims 5 to 9 in ceramic capacitors.

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