A wide temperature stable high dielectric low loss ceramic capacitor dielectric material and its preparation method and application

Abstract

The present invention relates to ceramic capacitor dielectric materials, and specifically to a wide temperature stable high dielectric low loss ceramic capacitor dielectric material and its preparation method and application. 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, of which x The dielectric constant is 0.10-0.18. This ceramic capacitor dielectric material is made from Bi2O3, BaCO3, SrCO3, TiO2, Fe2O3, Nb2O5, and Na2CO3. It exhibits a pure perovskite structure, characterized by characteristic peaks of both tetragonal and rhombohedral phases, and nanodomains within the ceramic grains. This ceramic capacitor dielectric material offers advantages such as wide temperature stability, high dielectric constant, and low dielectric loss, making it suitable for the manufacture of ceramic capacitors operating under high-temperature conditions.

Description

Technical Field

[0001] The present invention relates to ceramic capacitor dielectric materials, and in particular to a wide-temperature stable high-dielectric-low-loss ceramic capacitor dielectric material, a preparation method and an application thereof. Background Art

[0002] Capacitors, as an important charge storage component, effectively perform various functions in electronic systems, including filtering, bypassing, coupling, decoupling, pulse discharge, DC blocking, and power regulation. Ceramic capacitors use ceramic materials as their dielectric material. They come in a wide variety of types, with a wide range of dimensions. Based on their temperature coefficient and dielectric constant, they can be categorized as negative, positive, zero, high, and low dielectric constant. Furthermore, they are classified as Type I, Type II, and Type III. Multilayer ceramic capacitors (MLCCs) are widely used in automotive electronics, consumer electronics, aerospace, and weaponry due to their high capacitance, compact size, and excellent frequency, temperature, and voltage resistance. my country leads the world in MLCC demand, accounting for over 40% of global demand. However, due to technological limitations, the domestically produced MLCC supply rate is less than 10%. With the miniaturization and integration of electronic end products and the diversification of their service environments, high capacity, small size, high and low temperature resistance, high voltage resistance, and high reliability are the main development trends for high-end MLCCs. This puts higher demands on the dielectric properties of key ceramic dielectric materials, requiring them to have a stable dielectric constant over an extremely wide temperature range. At the same time, in order to meet the large capacity, high voltage resistance and high reliability requirements of capacitors, ceramic dielectric materials should also have both high dielectric constant and low dielectric loss.

[0003] The main ceramic material of commercial high-capacity MLCC is barium titanate (BaTiO3). The room temperature dielectric constant of commercial BaTiO3 system is ε r ~2000, Curie temperature T C ~120℃, this medium temperature characteristic is difficult to meet the temperature stability requirements. The temperature stability can be improved by modifying the "core-shell" structure, broadening the Curie peak or moving the Curie temperature out of the working temperature range. However, the operating temperature of the X7R type MLCC currently in large-scale commercial use on the market is -55~125℃ (room temperature). ε r : 2000~3000, temperature change rate ΔC / C 25 ℃ ≤ ±15%), the operating temperature of the advanced X9R MLCC is -55~200℃ (room temperature ε r: 1000~1500), limited by the low Curie temperature and sharp dielectric peak of BaTiO3, it is difficult to break through the higher and lower operating temperature limits. Once the operating temperature range is exceeded, the capacity of the MLCC device decreases, the loss increases, and the temperature stability, voltage resistance and reliability are significantly reduced. Patent documents with application numbers CN200710048476.2 (CN101033132A), CN202210715016.5 (publication number CN115159977A), and CN202410373599.7 (publication number CN118530018A) all disclose ceramic capacitor dielectric materials based on BaTiO3. Although the dielectric constant ε r The high-temperature stability is relatively high, but it is poor and cannot exceed the operating temperature range of 200°C. Patent document CN201910430453.0 (publication number CN110128132A) discloses a CaZrO3-based ultra-wide-temperature multilayer lead-free ceramic capacitor dielectric material with improved stability over a wide temperature range, but the dielectric constant is limited and does not exceed 840.

[0004] In certain scenarios, electronic systems may face extreme high-temperature conditions. For example, aircraft control systems monitor the engine combustion status in real time, and related electronic devices need to be as close to the engine as possible, and may need to withstand high temperatures of 200–500°C. The operating temperature 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 operate in high-temperature extreme environments. Therefore, there is an urgent need to seek new high-dielectric, low-loss ceramic dielectric material systems that are stable over a wide temperature range, and to conduct performance optimization research to meet the application of ceramic capacitors in extreme environments. Summary of the Invention

[0005] To address the above issues, the present invention provides a wide-temperature stable, high-k, low-loss ceramic capacitor dielectric material, as well as a preparation method and application. Specifically, it provides a wide-temperature stable, high-k, low-loss ceramic capacitor dielectric material, as well as a preparation method and application of the ceramic capacitor dielectric material.

[0006] First, the present invention provides a ceramic capacitor dielectric material that is stable over a wide temperature range, has a high dielectric constant, and has low dielectric loss. 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.

[0007] The ceramic capacitor dielectric material is made of Bi2O3, BaCO3, SrCO3, TiO2, Fe2O3, Nb2O5 and Na2CO3 as raw materials.

[0008] The X-ray diffraction spectrum of the ceramic capacitor dielectric material shows a pure perovskite structure with characteristic peaks of tetragonal and rhombohedral phases; and nano-domain structures exist in the ceramic grains of the ceramic capacitor dielectric material.

[0009] Preferably, the x is 0.10~0.15; further preferably, x is 0.12.

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

[0011] Secondly, the present invention provides a method for preparing the aforementioned ceramic capacitor dielectric material, comprising the following steps:

[0012] S1 Na2CO3 pretreatment: Na2CO3 powder was dried on a temperature-controlled magnetic stirrer at 200 °C for 3 h to prepare Na2CO3 material;

[0013] S2. Batching and first grinding: Batching is performed according to the nominal chemical composition, and Bi2O3, BaCO3, SrCO3, TiO2, Fe2O3, Nb2O5, and the Na2CO3 material prepared in step S1 are weighed as raw materials according to the stoichiometric ratio of the metal atoms in the nominal chemical composition expression; the raw materials are placed in a ball mill, and zirconia balls and anhydrous ethanol are used as ball milling media. The raw materials are placed in a planetary ball mill, and after ball milling, they are dried and passed through a 150-mesh sieve to obtain a mixed material A; the mixed material A is heated to 850°C in an air atmosphere at a heating rate of 5°C / min, kept at this temperature for 5 hours, and then cooled in the furnace to obtain a calcined powder;

[0014] S3 Second grinding: The calcined powder obtained in step S2 is poured into a ball mill jar with anhydrous ethanol and zirconium oxide, and then placed in a planetary ball mill. After ball milling, the mixture is dried and passed through a 200-mesh sieve to obtain a mixed material B;

[0015] S4 Granulation and Sintering: Add 3% by mass of polyvinyl butyral to the mixed material B and grind thoroughly until the powder is granular to obtain uniform granular powder. Take the granulated powder and press it into a cylindrical green body with a diameter of approximately 10 mm at a pressure of 20 MPa for 5 minutes. Place the green body in a crucible and calcine it with pre-calcined powder of the same composition. First, increase the temperature at a rate of 1°C / min to 500°C and hold it for 3 hours to remove the binder. Then increase the temperature at a rate of 5°C / min to 1200°C and hold it for 3 hours. Sinter and cool naturally in the furnace to obtain the ceramic material. In addition to the cylindrical green body with a diameter of approximately 10 mm, the shape or specifications of the ceramic green body can be selected from a variety of options in the art, such as 8 mm cylindrical green bodies, rectangular green bodies, etc.

[0016] Preferably, in step S2, the mass ratio of the raw material, anhydrous ethanol and zirconia balls is 1:1:3.

[0017] Preferably, in step S2, the preparation conditions of the mixed material A are: ball milling at a speed of 250 rpm for 18 hours, and then drying at 70° C. for 24 hours.

[0018] Preferably, in step S3, the mass ratio of the calcined powder, anhydrous ethanol and zirconium oxide is 15:20:45.

[0019] 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.

[0020] Finally, the present invention provides applications of the aforementioned ceramic capacitor dielectric material in the preparation of ceramic capacitors, particularly in the preparation of ceramic capacitors for use in high-temperature operating conditions. For example, ceramic capacitors for aircraft control systems that monitor engine combustion status in real time can be used.

[0021] 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 When TiO3 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+ Ion coexistence; Ti in B site 4+ 、Fe 3+ and Nb 5+Ion coexistence: Whether at the A or B site, the coexistence of cations with different valence states and ionic radii leads to a significant enhancement of the random field in the material, the destruction of the long-range ferroelectric ordered structure, the emergence of nanodomain structure, the decrease in the size of the polar region and the reduction in the degree of coupling, which significantly enhances the dielectric relaxation of the ceramic, which is reflected in the broadening and depression of the dielectric peak in the dielectric temperature spectrum. x When the dielectric constant is 0.10-0.15, a high and flat dielectric constant platform is formed, extending the high temperature end of the metastable range to 300℃.

[0022] The research found that the ceramic capacitor dielectric material of the present invention, Sr 2+ 、Fe 3+ 、Nb 5+ The content of the dielectric constant, dielectric loss and temperature stability of the dielectric material have an important influence on the dielectric constant, dielectric loss and temperature stability of the dielectric material. x When the dielectric constant is between 0.10 and 0.15, surprisingly excellent dielectric properties can be achieved. Below the lower limit, the dielectric constant at low temperatures drops significantly, dielectric loss increases, and the temperature stability of the dielectric properties is poor. Above the upper limit, the dielectric constant at high temperatures drops again significantly, dielectric loss increases, and the temperature stability of the dielectric properties is also poor.

[0023] Beneficial effects of the present invention:

[0024] This invention provides a ceramic capacitor dielectric material with excellent dielectric properties and temperature stability. Its relative dielectric constant remains between 2500 and 3000°C within the temperature range of 50°C to 300°C, its temperature gradient is less than 15% within this range, and its dielectric loss is less than 0.02 within the temperature range of 80°C to 300°C. This material is a high-dielectric, low-loss ceramic capacitor dielectric material with wide temperature stability. Its high-temperature dielectric properties and temperature stability significantly surpass those of commercial barium titanate-based dielectric ceramic materials, making it suitable for use in high-temperature capacitors, such as those operating at 50°C to 300°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The XRD pattern and nanodomain structure of the ceramic of Example 1;

[0026] Figure 2 The dielectric temperature spectrum and the capacitance-temperature change rate curve at 1 kHz of the ceramic in Example 1 are as follows;

[0027] Figure 3 The curve of the change of DC resistivity of the ceramic in Example 1 with temperature;

[0028] Figure 4 is the XRD pattern of the ceramic of Example 2;

[0029] Figure 5The dielectric temperature spectrum and the capacitance-temperature change rate curve at 1 kHz of the ceramic in Example 2 are as follows;

[0030] Figure 6 is the XRD pattern of the ceramic of Example 3;

[0031] Figure 7 The dielectric temperature spectrum and the capacitance-temperature change rate curve at 1 kHz of the ceramic in Example 3 are as follows;

[0032] Figure 8 is the XRD pattern of the ceramic of Comparative Example 1;

[0033] Figure 9 The dielectric temperature spectrum and the capacitance-temperature change rate curve at 1 kHz of the ceramic in comparative example 1 are as follows;

[0034] Figure 10 is the XRD pattern of the ceramic of Comparative Example 2;

[0035] Figure 11 The dielectric temperature spectrum of the ceramic in comparative example 2 and the capacitance-temperature change rate curve at 1 kHz with temperature change curve. DETAILED DESCRIPTION

[0036] The scheme and effect of the present invention are described below by specific examples. The examples are only used to illustrate and display the present invention, rather than to limit the scope of protection of the present invention. The present invention provides a nominal chemical composition (Bi 0.47 Na 0.47 Ba 0.06 ) 1-x Sr x Ti 1-x Fe x / 2 Nb x / 2 O3 ceramic capacitor dielectric material and preparation method, and show its performance characteristics, including x It is 0.10~0.15.

[0037] Example 1 A wide temperature range stable high-dielectric low-loss ceramic capacitor dielectric material and its preparation method

[0038] This embodiment provides 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 O3, that is x =0.12 high-dielectric-low-loss ceramic capacitor dielectric material and preparation method thereof.

[0039] Preparation of dielectric materials for high dielectric constant and low loss ceramic capacitors:

[0040] (1) Na2CO3 powder was dried at 200°C for 3 h on a temperature-controlled magnetic stirrer to prepare Na2CO3 material;

[0041] (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 O3 is used for mixing, and Bi2O3, BaCO3, SrCO3, TiO2, Fe2O3, Nb2O5 and Na2CO3 prepared in step (1) are weighed as raw materials according to the chemical molar ratio of metal atoms in the nominal chemical composition expression; the raw materials are placed in a ball mill, and zirconia balls and anhydrous ethanol are used as ball milling media. The mass ratio of raw materials, anhydrous ethanol and zirconia balls is 1:1:3. The raw materials are placed in a planetary ball mill and ball milled at a speed of 250 rpm for 18 h. The ball mill is taken out, dried at 70 ° C for 24 h, 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 warm for 5 h, and then cooled in the furnace to obtain a pre-sintered powder. Pre-burned powder, anhydrous ethanol and zirconium oxide balls are taken in a mass ratio of 15:20:45, poured into a ball mill, placed in a planetary ball mill, ball-milled at 400 rpm for 12 hours, then dried at 70°C for 24 hours, and passed through a 200-mesh sieve to obtain a mixed material B. Polyvinyl butyral with a mass fraction of 3% is added to the mixed material B, and the powder is fully ground until it becomes 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 at a pressure of 20Mpa for 5 minutes. The above green body is placed in an alumina crucible and buried with pre-burned powder of the same composition. First, the temperature is increased at a rate of 1°C / min to 500°C and kept for 3 hours to remove the binder, and then the temperature is increased at a rate of 5°C / min to 1200°C and kept for 3 hours to sinter. It is naturally cooled 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 O3 ceramic material.

[0042] Structural characterization of ceramic materials: X-ray diffraction (XRD) is used to analyze the crystal structure of ceramic materials, such as Figure 1 As shown in (a), it can be seen that the prepared ceramic material is a pure perovskite structure without the presence of impurity phases, proving that Sr 2+ 、Fe 3+ 、Nb 5+ Already dissolved in Bi 0.47 Na 0.47 Ba0.06 TiO3, present in XRD pattern (131) R and (312) R Peak is the characteristic peak of the rhombohedral phase and exists at the same time (002) T The peak is a characteristic peak of the tetragonal phase. The phase structure analysis results show that the tetragonal phase and the rhombohedral phase coexist in the ceramic material. The obtained ceramic material was subjected to transmission electron microscopy (TEM) detection. Figure 1 (b) As can be seen, randomly dispersed nanodomain structures exist within the ceramic grains. Nanodomain structures are regional structures formed at the nanoscale. These structures play a key role in ferroelectric materials, increasing the polarization strength of the material through highly localized strong polar states, thereby affecting the material's energy storage density and efficiency.

[0043] Characterization of electrical properties of ceramic materials: The sintered ceramics were polished to a thickness of 0.5 mm, coated with medium-temperature silver paste on both sides, and sintered at 550°C for 30 minutes to form silver electrodes for electrical performance testing. The dielectric constant ε of the ceramics was tested using a high-temperature impedance analyzer. r and dielectric loss tan δ The temperature and frequency curves are as follows. In this test, the test temperature range is 25~400℃ and the test frequencies include 1kHz, 10kHz and 100kHz. Then, the capacitance temperature change rate Δ at 1kHz is calculated using the measured dielectric temperature spectrum. C / C 150°C The temperature stability of ceramic dielectric capacitors is evaluated by measuring the change in (capacitance at a certain temperature - capacitance at 150°C) / capacitance at 150°C) over temperature.

[0044] Figure 2 is the dielectric temperature spectrum and capacitance temperature change rate of the ceramic C / C 150°C The dielectric temperature spectrum shows obvious dielectric peak broadening and frequency dispersion with temperature changes, proving the existence of temperature-dependent diffuse phase transition in ceramics. The standard room temperature dielectric constant is 1955 at 1kHz, the dielectric constant at 150℃ is as high as 2820, the dielectric loss is as low as 0.0095, and the temperature change rate Δ C / C 150°C Less than 15%, and the dielectric loss is less than 0.02 in the temperature range of 80-300℃.

[0045] The curve of the ceramic DC resistivity changing with temperature was obtained by using a DC resistance tester. The test temperature range in this test was 25~400℃. It can be seen that the room temperature resistivity is as high as 10 13 Ω•cm, until the resistivity is higher than 10 at 300℃9 Ω•cm, proving the excellent insulation performance of the ceramic.

[0046] Example 2 A wide temperature range stable high-dielectric low-loss ceramic capacitor dielectric material and its preparation method

[0047] Compared with Example 1, the only difference is 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 O3 (preparation method is the same as in Example 1, and electrical properties and other performance measurement methods are the same as in Example 1).

[0048] The XRD pattern of the ceramic material, the dielectric temperature spectrum and the capacitance-temperature variation curve at 1kHz are shown in Figure 2. Figure 4 、 5 .

[0049] The XRD results show that the ceramic material prepared in this embodiment still has a pure perovskite structure without impurity phases. The rhombic and tetragonal phases still coexist in the ceramic, but the rhombic and tetragonal lattice distortions are slightly higher than those of the ceramic material in Example 1.

[0050] From the dielectric temperature spectrum and the capacitance temperature change rate curve, it can be seen that the standard room temperature dielectric constant of the ceramic material prepared in this embodiment is 2005 at 1kHz, the dielectric constant at 150℃ is as high as 2820, the dielectric loss is 0.012, and the capacitance temperature change rate Δ C / C 150°C Less than 15%, and the dielectric loss is less than 0.02 in the temperature range of 90-320℃.

[0051] Example 3 A wide temperature range stable high dielectric low loss ceramic capacitor dielectric material and its preparation method

[0052] Compared with Example 1, the only difference is x =0.15, that is, the nominal chemical composition is Bi 0.3995 Na 0.3995 Ba 0.051 Sr 0.1 5Ti 0.85 Fe 0.075 Nb 0.075 O3 (preparation method is the same as in Example 1, and electrical properties and other performance measurement methods are the same as in Example 1).

[0053] The XRD pattern of the ceramic material, the dielectric temperature spectrum and the capacitance-temperature variation curve at 1kHz are shown in Figure 2. Figure 6 、 7 .

[0054] The XRD results show that the ceramic material prepared in this example still has a pure perovskite structure, without the presence of impurity phases, and the rhombohedral and tetragonal phases still coexist in the ceramic, but the rhombohedral and tetragonal lattice distortions are slightly lower than those of the ceramic material in Example 1. The dielectric temperature spectrum and the dielectric constant-temperature change curve show that the standard room temperature dielectric constant of the ceramic at 1kHz is 1940, the dielectric constant at 150°C is as high as 2615, the dielectric loss is as low as 0.008, and the dielectric constant-temperature change rate Δ is 0.008 in the temperature range of 50-300°C. C / C 150°C Less than 15%, and the dielectric loss is less than 0.02 in the temperature range of 75-290℃.

[0055] Comparative Example 1 A ceramic capacitor dielectric material and its preparation method

[0056] Compared with Example 1, the difference is that the nominal chemical composition is Bi 0.47 Na 0.47 Ba 0.06 TiO3, the preparation method of the ceramic capacitor dielectric material is as follows:

[0057] According to the nominal chemical composition Bi 0.47 Na 0.47 Ba 0.06TiO3 was used for the preparation of ingredients. Bi2O3, Na2CO3, BaCO3, and TiO2 raw materials were weighed according to the molar ratio. Na2CO3 powder was dried at 200°C for 3 hours on a temperature-controlled magnetic stirrer before weighing before use. All prepared raw materials were placed in a ball mill, using zirconium oxide balls and anhydrous ethanol as the ball milling media. The mass ratio of raw materials, anhydrous ethanol, and zirconium balls was 1:1:3. The mixture was placed in a planetary ball mill and ball milled at 250 rpm for 18 hours. The ball mill was removed from the ball mill, dried at 70°C for 24 hours, and passed through a 150-mesh sieve to obtain a mixed material A. This was heated to 850°C in an air atmosphere at a heating rate of 5°C / min. After holding for 5 hours, it was cooled in the furnace to obtain a pre-calcined powder. The pre-burned powder, anhydrous ethanol and zirconium balls were poured into a ball mill at a ratio of 15:20:45, placed in a planetary ball mill, ball-milled at 400 rpm for 12 hours, then dried at 70°C for 24 hours, and passed through a 200-mesh sieve to obtain a mixed material B. Polyvinyl butyral with a mass fraction of 3% was added to the mixed material B, and the mixture was fully ground until the powder was granular to obtain a granulated powder with uniform particles. 0.3g of granulated powder was taken and pressed into a cylindrical green body with a diameter of about 10mm at a pressure of 20Mpa for 5 minutes. The above green body was placed in an alumina crucible and buried with pre-burned powder of the same composition. First, the temperature was increased at a rate of 1°C / min to 500°C and kept for 3 hours to remove the binder, and then the temperature was increased at a rate of 5°C / min to 1200°C and kept for 3 hours to sinter, and naturally cooled with the furnace to obtain Bi. 0.47 Na 0.47 Ba 0.06 TiO3 ceramic material.

[0058] The crystal structure was analyzed by XRD, and the dielectric temperature spectrum was tested by high temperature impedance analyzer (the electrical performance characterization and other performance measurement methods are the same as those in Example 1). The XRD pattern, dielectric temperature spectrum and the capacitance temperature change rate at 1kHz of the ceramic material are shown in Figure 1. Figure 8 、 9 .

[0059] The XRD results show that the prepared ceramic material still has a pure perovskite structure without impurity phases. The rhombic and tetragonal phases still coexist in the ceramic, but the rhombic and tetragonal lattice distortions are significantly higher than those of the ceramic material in Example 1.

[0060] From the dielectric temperature spectrum and capacitance-temperature change rate curve, it can be seen that the standard room temperature dielectric constant of the ceramic at 1kHz is 1535, the dielectric constant at 150℃ is 4233, the dielectric loss is as high as 0.034, the temperature range for the dielectric constant change rate is less than 15% is only 120~203℃, and the temperature range for the dielectric loss is less than 0.02 is 155~350℃.

[0061] Comparative Example 2 A ceramic capacitor dielectric material and its preparation method

[0062] Compared with Example 1, the only difference is x =0.20, that is, the nominal chemical composition is Bi 0.376 Na 0.376 Ba 0.048 Sr 0.20 Ti 0.80 Fe 0.10 Nb 0.10 O3 (preparation method is the same as in Example 1, and electrical properties and other performance measurement methods are the same as in Example 1).

[0063] The XRD pattern of the ceramic material, the dielectric temperature spectrum and the capacitance-temperature variation curve at 1kHz are shown in Figure 2. Figure 10 、 11 .

[0064] The XRD results show that the prepared ceramic material still has a pure perovskite structure without impurity phases. The rhombic and tetragonal phases still coexist in the ceramic, but the rhombic and tetragonal lattice distortions are significantly lower than those of the ceramic material in Example 1.

[0065] From the dielectric temperature spectrum and capacitance-temperature change rate curve, it can be seen that the standard room temperature dielectric constant of the ceramic at 1kHz is 1640, the dielectric constant at 150℃ is 2048, the dielectric loss is 0.0086, the temperature range in which the dielectric constant change rate is less than 15% is only 25-250℃, and the temperature range in which the dielectric loss is less than 0.02 is 50-300℃.

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 0.10~0.18; The ceramic capacitor dielectric material is made of Bi2O3, BaCO3, SrCO3, TiO2, Fe2O3, Nb2O5 and Na2CO3 as raw materials; The X-ray diffraction pattern of the ceramic capacitor dielectric material shows a pure perovskite structure with characteristic peaks of tetragonal and rhombohedral phases; nanodomain structures exist in the ceramic grains of the ceramic capacitor dielectric material; and the preparation method of the ceramic capacitor dielectric material is characterized by comprising the following steps: S1 Na2CO3 pretreatment: Na2CO3 powder was dried at 200℃ for 3h to prepare Na2CO3 material; S2. Batching and first grinding: Batching is performed according to the nominal chemical composition, and Bi2O3, BaCO3, SrCO3, TiO2, Fe2O3, Nb2O5, and the Na2CO3 material prepared in step S1 are weighed as raw materials according to the stoichiometric ratio of the metal atoms in the nominal chemical composition expression; the raw materials are placed in a ball mill, and zirconia balls and anhydrous ethanol are used as ball milling media. The raw materials are placed in a planetary ball mill, and after ball milling, they are dried and passed through a 150-mesh sieve to obtain a mixed material A; the mixed material A is heated to 850°C in an air atmosphere at a heating rate of 5°C / min, kept at this temperature for 5 hours, and then cooled in the furnace to obtain a calcined powder; S3 Second grinding: The calcined powder obtained in step S2 is poured into a ball mill jar with anhydrous ethanol and zirconium oxide, and then placed in a planetary ball mill. After ball milling, the mixture is dried and passed 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 20 MPa 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°C / min to 500°C and keep it for 3 hours to remove the binder, then increase the temperature at a rate of 5°C / min to 1200°C and keep it for 3 hours to sinter, and cool it naturally in the furnace to obtain ceramic material.

2. The ceramic capacitor dielectric material according to claim 1, wherein described x It is 0.10~0.

15.

3. The ceramic capacitor dielectric material according to claim 1, wherein In step S2, the mass ratio of the raw material, anhydrous ethanol and zirconia balls is 1:1:

3.

4. The ceramic capacitor dielectric material according to claim 1, wherein In step S2, the preparation conditions of the mixed material A are: ball milling at a speed of 250 rpm for 18 hours, and then drying at 70°C for 24 hours.

5. The ceramic capacitor dielectric material according to claim 1, wherein In step S3, the mass ratio of the calcined powder, anhydrous ethanol and zirconium oxide is 15:20:

45.

6. The ceramic capacitor dielectric material according to claim 1, wherein 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.

7. Use of the ceramic capacitor dielectric material according to any one of claims 1 to 5 in ceramic capacitors.

Images