An ultra-wide temperature stable sodium bismuth titanate-based dielectric ceramic material and its preparation method

Abstract

The present invention discloses an ultra-wide temperature stable sodium bismuth titanate-based dielectric ceramic material and a preparation method thereof, wherein the chemical formula is (1-x)(0.94Bi 0.5 Na 0.5 TiO3‑0.06BaTiO3)‑xCa(Fe 0.5 Ta 0.5 )O3, where x is 0.18-0.22. The sodium bismuth titanate-based dielectric ceramic material can be prepared using a traditional solid-phase method and has excellent dielectric properties and temperature stability: a room temperature dielectric constant of 670 at 1 kHz, a dielectric loss as low as 0.0037, a dielectric constant change rate of less than 15% within the temperature range of -150 to 450°C, and a dielectric loss of less than 0.02 within the temperature range of -110 to 300°C. The ultra-wide temperature-stable sodium bismuth titanate-based dielectric ceramic material provided by the present invention is suitable for use in ceramic dielectric capacitors in extreme high and low temperature environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of lead-free dielectric ceramics, and in particular relates to a sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability and a preparation method thereof. Background Art

[0002] Dielectric ceramic capacitors 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 characteristics. In certain scenarios, dielectric ceramic capacitors face extreme operating conditions such as high temperature, severe cold, high pressure, and high impact, which place extremely high demands on the high and low temperature stability of the dielectric properties of key dielectric ceramic materials. For example, related electronic devices in aircraft and automobile engine monitoring systems may need to withstand high temperatures of 300 to 600°C. Currently, commercial high-capacity dielectric ceramic capacitors mainly use barium titanate as raw material, and the operating temperature range of the prepared devices is limited to -55 to 200°C. Due to the low Curie temperature of barium titanate (~120°C), the upper temperature limit of use is difficult to break. Once the temperature exceeds 200°C, the capacitor's capacitance decreases, losses increase, and temperature stability, voltage resistance, and reliability are significantly reduced. Therefore, there is an urgent need to develop new dielectric ceramic materials with a wider operating temperature range to meet more extreme high and low temperature working environments.

[0003] Sodium bismuth titanate (Bi 0.5 Na 0.5 TiO3 (BNT) is a type of relaxor ferroelectric with a perovskite structure. There are two unique dielectric anomaly peaks in its dielectric temperature spectrum, namely T s (~200℃, dielectric constant ~1500) hump and T m The maximum dielectric constant peak at (~320℃, dielectric constant ~3000) is conducive to achieving wide temperature stabilization of the dielectric constant. The dielectric anomaly of BNT originates from the thermal evolution of the trigonal R3c and tetragonal P4bm polar nano-microdomains with similar free energy in the material at the local scale. If doping / solid solution modification is used, the relative content, size or polarization ability of the polar nano-microdomains can be changed to increase the T s By moving it below room temperature and suppressing the dielectric abnormal peak, it is expected that the T s -T m A flat and wide dielectric temperature curve is obtained in the temperature range. However, due to the T s It is too high to reach 200℃, so it is difficult to extend the low temperature section of the metastable range to below -100℃ in BNT-based ceramics. On the other hand, the T m ~320℃, so it is also very challenging to extend the high temperature end of the metastable range to above 400℃. Summary of the Invention

[0004] In response to the shortcomings of the prior art, the first object of the present invention is to provide a sodium bismuth titanate-based dielectric ceramic material with an ultra-wide temperature stability having a high dielectric constant and low dielectric loss, while the dielectric properties have very excellent temperature stability. The sodium bismuth titanate-based dielectric ceramic material provided by the present invention is suitable for use in ceramic dielectric capacitors in extreme high and low temperature environments.

[0005] The second object of the present invention is to provide a method for preparing the above-mentioned ultra-wide temperature stable sodium bismuth titanate-based dielectric ceramic material. The present invention adopts a traditional solid-phase method, and the preparation process is simple and controllable.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention discloses a sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability. The sodium bismuth titanate-based dielectric ceramic material has the chemical formula (1-x)(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-xCa(Fe 0.5 Ta 0.5 )O3, wherein x is 0.18-0.22, preferably 0.20.

[0008] The sodium bismuth titanate-based dielectric ceramic material provided by the present invention, 0.94Bi 0.5 Na 0.5 There are two abnormal dielectric peaks in the TiO3-0.06BaTiO3 matrix, namely T s The hump at s ~100℃) and T m The maximum dielectric constant peak (T m ~260℃). Doped with Ca(Fe 0.5 Ta 0.5 )O3, Ca 2+ ions enter the A site of the perovskite structure and interact with the Bi 3+ 、Na + and Ba 2+ Ion coexistence; Fe 3+ and Ta 5+ ions enter the B site of the perovskite structure and interact with the Ti 4+ 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 a 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. When x is 0.18-0.22, T s has dropped to about -150℃, T mIt is difficult to identify, forming a flat and low dielectric constant platform, extending the low-temperature end and high-temperature end of the metastable range to below -100°C and above 400°C respectively.

[0009] The sodium bismuth titanate-based dielectric ceramic material provided by the present invention has a high dielectric constant of 670 and a low dielectric loss of 0.0037 at room temperature. At the same time, the dielectric constant change rate is less than 15% in the temperature range of -150 to 450°C, and the dielectric loss is less than 0.02 in the temperature range of -110 to 300°C.

[0010] The sodium bismuth titanate-based dielectric ceramic material provided by the present invention, Ca(Fe 0.5 Ta 0.5 The solid solubility of )O3 significantly influences the room-temperature dielectric constant, dielectric loss, and temperature stability of sodium bismuth titanate-based dielectric ceramics. Controlling the solid solubility to 18-22 mol% demonstrates surprisingly excellent performance. Studies have found that below this lower limit, the room-temperature dielectric constant and dielectric loss are high, and the temperature stability of the dielectric properties is poor. Excessive solid solubility can lead to the appearance of impurity phases in the ceramic.

[0011] Preferably, the tetragonal P4bm phase, the orthorhombic Pnma phase and the trigonal R3c phase coexist in the sodium bismuth titanate-based dielectric ceramic material;

[0012] The grains of the sodium bismuth titanate-based dielectric ceramic material contain a blocky nanodomain structure;

[0013] The grain size of the sodium bismuth titanate-based dielectric ceramic material is 1.79 to 2.37 μm.

[0014] The sodium bismuth titanate-based dielectric ceramic material provided by the present invention, Ca(Fe 0.5 Ta 0.5 )O3 doped with 0.94Bi 0.5 Na 0.5 After the TiO3-0.06BaTiO3 matrix is ​​doped, the random field in the ceramic is significantly enhanced due to the diversity of ion valence and ion radius, destroying the long-range ferroelectric ordered structure and forming a nano-domain structure. On the other hand, 0.94Bi 0.5 Na 0.5 There is a tetragonal P4bm phase (accounting for about 97.7wt%, a 0 a 0 c + type oxygen octahedron tilted) and trigonal R3c phase (about 2.3wt%, a - a - a - type oxygen octahedron tilted), while Ca(Fe 0.5 Ta 0.5)O3 doping significantly reduces the perovskite structure tolerance factor from 0.984 (x = 0) to 0.962 (x = 0.20), inducing a 0 a 0 c + The inclined tetragonal P4bm oxygen octahedron faces a - a - c + The tilted orthorhombic Pnma phase of the oxygen octahedra transforms to a three-phase coexistence structure. In the x = 0.20 ceramic, the tetragonal P4bm phase accounts for 58.8wt%, the orthorhombic Pnma phase accounts for 33.3wt%, and the trigonal R3c phase accounts for 7.9wt%. The multiphase coexistence and nanodomain structure promote a diffuse phase transition with temperature, resulting in excellent temperature stability of the dielectric properties.

[0015] The present invention also provides a method for preparing an ultra-wide temperature stable sodium bismuth titanate-based dielectric ceramic material, according to (1-x)(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-xCa(Fe 0.5 Ta 0.5 )O3 is prepared by mixing raw material powders in a stoichiometric ratio of elements, and ball milling is performed for the first time to obtain a mixed material A, the mixed material A is pre-fired to obtain pre-fired powder, the pre-fired powder is ball milled for a second time to obtain a mixed material B, the mixed material B is granulated to obtain granulated powder, the granulated powder is pressed into shape to obtain a green body, and the green body is debinded and sintered to obtain a sodium bismuth titanate-based dielectric ceramic material.

[0016] The technical solution of the present invention is simple and controllable, with low cost. By adopting the traditional solid-phase method, after one pre-firing, an ultra-wide temperature stable sodium bismuth titanate-based dielectric ceramic material can be obtained. The method of the present invention can prepare a large amount of ceramic powder at one time with a large output, and the prepared ceramic powder has no agglomeration and good filling properties.

[0017] The preferred solution is based on (1-x)(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-xCa(Fe 0.5 Ta 0.5 )O3 is prepared in a stoichiometric ratio of elements including Bi2O3, Na2CO3, BaCO3, CaCO3, TiO2, Fe2O3 and Ta2O5 as raw materials.

[0018] In practice, to ensure experimental accuracy, some hygroscopic raw materials must be dried before weighing. For example, dry an appropriate amount of Na2CO3 powder on a temperature-controlled magnetic stirrer at 200°C for 3 hours before weighing. Weigh the mixture quickly at the end to minimize absorption of moisture from the air.

[0019] In addition, the raw materials are weighed according to the chemical formula, and the required amount of each drug is weighed using an electronic balance and placed in the ball mill. The amount of material has a significant impact on the performance of the ceramic, so the weighing should be accurate to three decimal places.

[0020] In a preferred embodiment, the rotation speed of the first ball milling is 200 to 300 rpm, and the time of the first ball milling is 12 to 24 hours.

[0021] In a preferred embodiment, the first ball milling is wet ball milling, and the ball milling medium is anhydrous ethanol, wherein the mass ratio of raw material powder, anhydrous ethanol, and ball milling balls is 1:1:3-5.

[0022] During the first ball milling, the mass ratio of the raw material powder, anhydrous ethanol, and ball milling balls is controlled within the range of the present invention, and the raw material powder can be fully mixed and refined by controlling the ball milling speed and time, thereby promoting a more complete subsequent reaction.

[0023] In actual operation, the raw materials, anhydrous ethanol, and zirconium balls are poured into a ball mill in appropriate proportions, ensuring that no impurities are introduced into the mill. A planetary ball mill is used, and the ball mill is sealed and placed inside the mill. After milling, the mill is removed and dried in a 70°C drying oven for 24-36 hours until the powder is completely dry. The powder is then passed through a 150-mesh sieve to completely separate the powder and zirconium balls, yielding a homogenized material A.

[0024] In a preferred embodiment, after the first ball milling is completed, the ball milled powder is dried and then passed through a 150-mesh sieve to obtain the mixed material A.

[0025] In a preferred embodiment, the pre-calcination process is as follows: the mixed material A is heated to 850-950°C in an air atmosphere at a heating rate of 3-8°C / min, kept at this temperature for 2-5 hours, and then cooled in the furnace. In order to allow the powder materials to fully react, pre-calcination is first performed to initially obtain pre-calcined powder.

[0026] In a preferred embodiment, the second ball milling has a rotation speed of 400 to 600 rpm and a time of 8 to 12 hours.

[0027] In a preferred embodiment, the second ball milling is wet ball milling, and the ball milling medium is anhydrous ethanol, wherein the mass ratio of the calcined powder, anhydrous ethanol, and ball milling balls is 15:20:45-60.

[0028] In the present invention, due to the complex composition of the ceramic system, the present invention adopts a higher ball milling speed on the one hand, and on the other hand, by controlling the mass ratio of pre-fired powder, anhydrous ethanol, and ball milling balls, a fine powder with a particle size distribution of 300 to 500 nm is obtained, and the composition of the pre-fired powder is further homogenized, which is ultimately beneficial to the subsequent sintering densification. Therefore, it is necessary to control the ball milling speed, etc. If the ball milling speed is too slow, it will lead to lower sintering activity and may also cause component segregation in the fired ceramic, thereby deteriorating the ceramic performance.

[0029] In actual operation, the calcined powder, anhydrous ethanol, and zirconium balls are poured into a ball mill in a proportional amount, ensuring that no impurities are introduced into the jar. A planetary ball mill is used, and the jar is sealed and placed inside the mill, secured. After milling, the jar is removed and dried in a 70°C drying oven for 24-36 hours until the powder is completely dry. The mixture is then passed through a 200-mesh sieve to completely separate the powder and zirconium balls, yielding a homogenized material B.

[0030] In a preferred embodiment, after the second ball milling is completed, the ball milled powder is dried and then passed through a 200-mesh sieve to obtain the mixed material B.

[0031] In a preferred embodiment, the process of granulating the mixed material B is as follows: a binder is added to the mixed material B and then the mixed material B is ground into granules, wherein the amount of the binder added is 3-5% of the mass of the mixture.

[0032] The binder can be a substance with adhesive properties well known in the granulation industry; preferably, polyvinyl butyral.

[0033] In a preferred embodiment, the pressing pressure is 20-30 MPa, and the holding time is 3-8 minutes.

[0034] In actual operation, 0.3 to 0.5 g of granulated powder is poured into a mold with a diameter of 10 mm and pressed into shape. The pressed green body is then subjected to debinding and sintering treatments in an air atmosphere.

[0035] In a preferred embodiment, the debinding and sintering process is as follows: first, heating the temperature to a debinding temperature of 550-650°C at a heating rate of 0.5-2°C / min and keeping the temperature for 2-4 hours; then heating the temperature to a sintering temperature of 1160-1200°C at a heating rate of 3-8°C / min and keeping the temperature for 2-4 hours.

[0036] Beneficial effects of the present invention:

[0037] (1) The present invention provides a sodium bismuth titanate-based dielectric ceramic material with excellent dielectric properties and temperature stability, which is solid-dissolved with the second component Ca(Fe 0.5 Ta 0.5 )O3,0.94Bi 0.5 Na 0.5The room-temperature dielectric loss of the TiO3-0.06BaTiO3 ceramic system has been greatly suppressed, and a relatively high room-temperature dielectric constant has been maintained; more importantly, the temperature-stable range of dielectric properties has been greatly widened, and the high dielectric constant and extremely low dielectric loss remain stable within an ultra-wide temperature range.

[0038] (2) The 0.80 (0.94 Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5 )O3 ceramics, the dielectric constant is 670 at room temperature 25℃, the dielectric loss is as low as 0.0037, the change rate of the dielectric constant is less than 15% in the temperature range of -150~450℃, and the dielectric loss is less than 0.02 in the temperature range of -110~300℃.

[0039] (3) The raw materials used in the present invention do not contain rare earth elements and precious metal elements, so the cost is low; and the raw materials do not contain lead, so they are harmless to the environment.

[0040] (4) The present invention extends the low temperature end of the dielectric ceramic temperature stability range to -150°C and the high temperature end to 450°C, which is significantly better than commercial barium titanate-based dielectric ceramic materials and the currently reported sodium bismuth titanate-based dielectric ceramic materials, and has great application prospects in high and low temperature dielectric ceramic capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 、0.80(0.94Bi in Example 1 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5 )X-ray diffraction patterns and phase structure refinement results of O3 ceramics.

[0042] Figure 2 、0.80(0.94Bi in Example 1 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5 )Scanning electron microscope image and particle size distribution of O3 ceramics.

[0043] Figure 3 、0.80(0.94Bi in Example 1 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5) Low-magnification transmission electron micrograph of O3 ceramics.

[0044] Figure 4 、0.80(0.94Bi in Example 1 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5 ) Dielectric properties test diagram of O3 ceramics, where Figure 4 (a) is the dielectric temperature spectrum, Figure 4 (b) Δε obtained using dielectric temperature spectrum r / ε r25 ℃ vs. T spectrum. DETAILED DESCRIPTION

[0045] Example 1

[0046] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings.

[0047] Example 1 of the present invention provides an ultra-wide temperature stable sodium bismuth titanate-based dielectric ceramic material and a preparation method thereof, wherein the chemical formula is 0.80(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5 )O3.

[0048] 0.80(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5 ) Preparation of O3 ceramic materials

[0049] Bi2O3, Na2CO3, BaCO3, CaCO3, TiO2, Fe2O3 and Ta2O5 raw materials were weighed respectively according to the molar ratio of 0.188:0.188:0.048:0.2:0.8:0.05:0.05. Before weighing, the Na2CO3 powder was dried at 200°C for 3 hours on a temperature-controlled magnetic stirrer. The raw materials were placed in a ball mill with zirconia balls and anhydrous ethanol as the medium. The mass ratio of raw materials, anhydrous ethanol and zirconium balls was 1:1:3. The raw materials were placed in a planetary ball mill and ball milled at 250 rpm for 18 hours. The ball mill was taken out, dried at 70°C for 24 hours, and passed through a 150-mesh sieve to obtain a mixed material A. The mixed material A was heated to 900°C at a heating rate of 5°C / min in an air atmosphere, kept warm for 3 hours, and then cooled in the furnace to obtain a pre-sintered 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 green body was placed in an alumina crucible and buried with pre-burned powder of the same composition. First, the temperature was increased to 600°C at a rate of 1°C / min and kept warm for 2 hours to remove the binder, and then the temperature was increased to 1180°C at a rate of 5°C / min and kept warm for 3 hours to sinter. The green body was naturally cooled in the furnace to obtain 0.80 (0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5 )O3 ceramic materials.

[0050] 0.80(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.20Ca(Fe 0.5 Ta 0.5 ) Characterization of O3 ceramic materials

[0051] Structural characterization: First, the crystal phase is detected by X-ray diffraction analysis (XRD). Figure 1 As shown, the prepared ceramic material has a pure perovskite structure, free of impurity phases. Phase structure refinement revealed the coexistence of tetragonal P4bm, orthorhombic Pnma, and trigonal R3c phases, with respective phase contents of 58.8wt%, 33.3wt%, and 7.9wt%, respectively.

[0052] The obtained ceramic material was subjected to scanning electron microscopy (SEM) inspection. Before the test, the ceramic was polished and thermally etched. Figure 2It can be seen that the prepared ceramics have no obvious defects, good crystallinity, uniform grain size and an average grain size of about 2.08 μm.

[0053] The obtained ceramic material was subjected to transmission electron microscopy (TEM) examination. Figure 3 It can be seen that there are bulk nanodomain structures in the ceramic grains.

[0054] Dielectric properties characterization: The sintered ceramic was 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 a silver electrode. The dielectric temperature spectrum test uses a high-temperature impedance analyzer to measure the dielectric constant ε of the ceramic. r The dielectric loss tanδ curve changes with temperature T and frequency f. In this test, the test temperature range is -160 ~ 450 ° C, and the test frequencies include 1kHz, 10kHz, 100kHz and 1MHz. Then, the measured dielectric temperature spectrum is used to calculate Δε at 1kHz. r / ε r25 The temperature stability of the dielectric constant of ceramics is evaluated by measuring the change of dielectric constant at a certain temperature point - dielectric constant at 25°C / dielectric constant at 25°C with temperature.

[0055] Figure 4 (a) is the dielectric temperature spectrum of the ceramic, showing obvious dielectric peak broadening and frequency dispersion, proving the existence of temperature-dependent diffuse phase transition in the ceramic. The room temperature dielectric constant is 670 at 1 kHz, the dielectric loss is as low as 0.0037, and the dielectric loss is less than 0.02 in the temperature range of -110 to 300 °C; (b) is the Δε at 1 kHz obtained using the dielectric temperature spectrum. r / ε r25 From the ℃ vs. T graph, we can see that the temperature stability of the ceramic dielectric constant is very good, and the change rate of the dielectric constant in the temperature range of -150 to 450℃ is less than 15%.

[0056] Example 2

[0057] Compared with Example 1, the only difference is that Ca(Fe 0.5 Ta 0.5 )O3 solid solution is 22 mol%, that is, the chemical formula is 0.78(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.22Ca(Fe 0.5 Ta 0.5)O3, the prepared ceramic still has a pure perovskite structure, free of impurity phases. The ceramic crystal phase composition is 49.9wt% P4bm phase, 41.5wt% Pnma phase, and 8.6wt% R3c phase, with an average grain size of 2.37μm. The room temperature dielectric constant is 635 at 1kHz, and the dielectric loss is as low as 0.0035. The temperature range for dielectric loss less than 0.02 is -115 to 300°C, and the temperature range for dielectric constant change less than 15% is -158 to 450°C.

[0058] Comparative Example 1:

[0059] Compared with Example 1, the only difference is that no solid solution of Ca(Fe 0.5 Ta 0.5 )O3, which has the chemical formula 0.94Bi 0.5 Na 0.5 The ceramics prepared using TiO3-0.06BaTiO3 exhibit a pure perovskite structure, free of impurity phases. The ceramic crystal phase composition is 97.7wt% P4bm phase and 2.3wt% R3c phase, with an average grain size of 1.26μm. The room-temperature dielectric constant is 2040 at 1kHz, and the dielectric loss is as high as 0.065. The temperature range for dielectric loss to be less than 0.02 is 128-400°C, and the temperature range for dielectric constant change to be less than 15% is only 105-185°C.

[0060] Comparative Example 2:

[0061] Compared with Example 1, the only difference is that Ca(Fe 0.5 Ta 0.5 )O3 solid solution is 10mol%, that is, the chemical formula is 0.90(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-0.10Ca(Fe 0.5 Ta 0.5 )O3, the prepared ceramic still has a pure perovskite structure, free of impurity phases. The ceramic crystal phase composition is 86.8wt% P4bm phase, 12.8wt% Pnma phase, and 0.4wt% R3c phase, with an average grain size of 1.64μm. The room temperature dielectric constant is 1082 at 1kHz, and the dielectric loss is as high as 0.030. The temperature range for dielectric loss less than 0.02 is 140-335°C, and the temperature range for dielectric constant change less than 15% is 85-375°C.

[0062] Comparative Example 3:

[0063] Compared with Example 1, the only difference is that Ca(Fe 0.5 Ta 0.5 )O3 solid solution is 25 mol%, that is, the chemical formula is 0.75(0.94Bi0.5 Na 0.5 TiO3-0.06BaTiO3)-0.25Ca(Fe 0.5 Ta 0.5 )O3, obvious impurity phase appears in the prepared ceramics.

Claims

1. A sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability, characterized by: The sodium bismuth titanate-based dielectric ceramic material, Its chemical formula is (1-x)(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-xCa(Fe 0.5 Ta 0.5 )O3, where x is 0.18-0.

22.

2. The sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability according to claim 1, characterized in that: The tetragonal P4bm phase, the orthorhombic Pnma phase and the trigonal R3c phase coexist in the sodium bismuth titanate-based dielectric ceramic material; The grains of the sodium bismuth titanate-based dielectric ceramic material contain a blocky nanodomain structure; The grain size of the sodium bismuth titanate-based dielectric ceramic material is 1.79 to 2.37 μm.

3. The method for preparing the ultra-wide temperature stable sodium bismuth titanate-based dielectric ceramic material according to claim 1 or 2, characterized in that: According to (1-x)(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-xCa(Fe 0.5 Ta 0.5 )O3 is prepared by mixing raw material powders in a stoichiometric ratio of elements, and ball milling is performed for the first time to obtain a mixed material A, the mixed material A is pre-fired to obtain pre-fired powder, the pre-fired powder is ball milled for a second time to obtain a mixed material B, the mixed material B is granulated to obtain granulated powder, the granulated powder is pressed into shape to obtain a green body, and the green body is debinded and sintered to obtain a sodium bismuth titanate-based dielectric ceramic material.

4. The method for preparing a sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability according to claim 3, characterized in that: According to (1-x)(0.94Bi 0.5 Na 0.5 TiO3-0.06BaTiO3)-xCa(Fe 0.5 Ta 0.5 )O3 is prepared in a stoichiometric ratio of elements including Bi2O3, Na2CO3, BaCO3, CaCO3, TiO2, Fe2O3 and Ta2O5 as raw materials.

5. The method for preparing a sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability according to claim 3, characterized in that: The rotation speed of the first ball milling is 200-300 rpm, and the time of the first ball milling is 12-24 hours; The first ball milling is wet ball milling, and the ball milling medium is anhydrous ethanol, wherein the mass ratio of raw material powder, anhydrous ethanol, and ball milling balls is 1:1:3-5; After the first ball milling is completed, the obtained ball milled powder is dried and then passed through a 150-mesh sieve to obtain the mixed material A.

6. The method for preparing a sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability according to claim 3, characterized in that: The pre-calcination process is as follows: heating the mixed material A to 850-950° C. at a heating rate of 3-8° C. / min in an air atmosphere, keeping the temperature for 2-5 hours, and then cooling the mixed material in the furnace.

7. The method for preparing a sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability according to claim 3, characterized in that: The second ball milling speed is 400-600 rpm, and the second ball milling time is 8-12 hours; The second ball milling is wet ball milling, and the ball milling medium is anhydrous ethanol, wherein the mass ratio of the calcined powder, anhydrous ethanol, and ball milling balls is 15:20:45-60; After the second ball milling is completed, the obtained ball milled powder is dried and then passed through a 200-mesh sieve to obtain the mixed material B.

8. The method for preparing a sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability according to claim 3, characterized in that: The process of granulating the mixed material B is as follows: adding a binder to the mixed material B and then grinding the mixed material B into granules, wherein the amount of the binder added is 3-5% of the mass of the mixed material B.

9. The method for preparing a sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability according to claim 3, characterized in that: The pressure of the compression molding is 20-30 MPa, and the holding time is 3-8 minutes.

10. The method for preparing a sodium bismuth titanate-based dielectric ceramic material with ultra-wide temperature stability according to claim 3, characterized in that: The debinding and sintering process is as follows: firstly, heating to a debinding temperature of 550-650°C at a heating rate of 0.5-2°C / min and keeping the temperature for 2-4 hours; then heating to a sintering temperature of 1160-1200°C at a heating rate of 3-8°C / min and keeping the temperature for 2-4 hours.

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