An underfilled tungsten bronze structure low-loss dielectric material and a preparation method thereof

Abstract

This invention discloses an unfilled tungsten bronze structure low-loss dielectric material, its applications, and its preparation method. The unfilled tungsten bronze structure low-loss dielectric material has the general structural formula aNb₂O₅-bCaO-cSrO-dBaO-eLa₂O₃-fNd₂O₃-gNa₂O, where a≥0.5, b≥0.1, c≥0.1, d≥0.1, e≥0, f≥0, and g≥0. This unfilled tungsten bronze structure low-loss dielectric material exhibits adjustable dielectric constant, low dielectric loss, and small capacitance-temperature variation rate, making it suitable for ceramic capacitors and MLCCs. Its preparation involves low-to-medium temperature sintering, making it environmentally friendly, simple to process, and low-cost, thus possessing good industrialization prospects.

Description

Technical Field

[0001] This invention relates to a low-loss dielectric material with an unfilled tungsten bronze structure and its preparation method, belonging to the technical field of ceramic materials for electronic components. Background Technology

[0002] Ceramic dielectric capacitors possess advantages such as rapid charging and discharging, high power density, resistance to cyclic aging, and resistance to high temperatures and high voltages, making them widely used in pulse power supplies, high-power electronic devices, and other fields. Key parameters of ceramic capacitors include capacitance-electric field relationship, dielectric constant, dielectric loss, capacitance-temperature coefficient, and operating temperature range. Materials with high dielectric loss not only consume more electrical energy, but the heat generated by the loss also makes the device more prone to failure. For example, according to EIA standards, X6R, X7R, and X9R ceramic capacitors are required to have a capacitance-temperature coefficient |ΔC / C25℃| ≤ ±15% at high temperatures of 105℃, 125℃, and 200℃, respectively; and a dielectric loss of less than 0.05.

[0003] The capacitance C of the capacitor and the relative permittivity ε of the dielectric material used r The relationship is: C = ε0ε r S / d (ε0 is the vacuum permittivity), where S is the area of ​​the capacitor electrode and t is the thickness of the dielectric material. That is, the change of the relative permittivity with temperature directly determines the capacitance-temperature change rate of the capacitor.

[0004] In existing technologies, the ceramic dielectric materials used in temperature-stable ceramic capacitors and widely used multilayer ceramic capacitors (MLCCs) mainly fall into two categories: lead-containing dielectric materials and barium titanate-based core-shell structure materials. Due to the harmful effects of lead on humans and the environment, barium titanate-based core-shell structure materials are the primary dielectric materials for temperature-stable ceramic capacitors and MLCCs, considering environmental and health factors. However, pure barium titanate undergoes a phase transition at approximately 120°C, affecting its capacitance stability and limiting its use at high temperatures. Therefore, developing ceramic capacitor dielectric materials with higher operating temperatures is crucial. Summary of the Invention

[0005] To address the aforementioned problems, one objective of this invention is to provide a low-loss dielectric material with a simple unfilled tungsten bronze structure, whose general structural formula is aNb2O5-bCaO-cSrO-dBaO-eLa2O3-fNd2O3-gNa2O. This ceramic dielectric material features an adjustable dielectric constant, low dielectric loss, low capacitance change rate, and a high temperature limit.

[0006] The second object of the present application is to provide a preparation method of the ceramic dielectric material for capacitors, specifically: firstly, mixing and grinding raw material powders of a certain molar ratio to obtain a mixture; secondly, pre-burning and finely grinding the mixture to obtain a pre-burning powder; thirdly, adding a binder to the pre-burning powder and granulating, and then pressing to obtain a green body; and finally, removing glue from the green body and sintering to obtain the ceramic dielectric material. The preparation method of the ceramic dielectric material is not limited to the present method, and new ceramic preparation technologies such as high-temperature co-firing technology can also produce similar or better performance.

[0007] To achieve the above-mentioned objects, the present application adopts the following scheme:

[0008] A non-full type tungsten bronze structure low-loss dielectric material, the structure general formula is aNb2O5-bCaO-cSrO-dBaO-eLa2O3-fNd2O3-gNa2O, wherein a≥0.5, b≥0.1, c≥0.1, d≥0.1, e≥0, f≥0, g≥0.

[0009] The inventors have found that, in the material of the specific composition of the present application, the introduction of La and Nd elements is beneficial to improve the dielectric constant of the dielectric system; the introduction of Ca and Na elements is beneficial to reduce the dielectric loss of the material and reduce the cost.

[0010] The elements and coefficients of inorganic materials have a great influence on the performance of the material. The inventors have found through experiments that, if the Ca element in the structure of the material of the present application is removed, the dielectric loss increases significantly, and the temperature stability is significantly deteriorated; if the Ca element is removed and Pb element or K and Ag elements are introduced, the dielectric loss increases significantly, the temperature stability is significantly deteriorated, the high-temperature limit value is significantly reduced, the environmental protection is deteriorated, and the cost is increased.

[0011] The raw materials used in the present application are low in cost, easy to obtain, and good in safety, without the need to use high-cost Ce, Y, etc., and without the need to use toxic Y, Gd, Ce, Mn, etc. The present application can better meet the diverse needs of different customers.

[0012] As a preferred technical scheme of the present application, in the structure formula aNb2O5-bCaO-cSrO-dBaO-eLa2O3-fNd2O3-gNa2O: a=0.5, b=0.125, c=0.125, d=0.125, e=0.0625, f=0, g=0; or a=0.5, b=0.125, c=0.125, d=0.125, e=0, f=0.0625, or g=0; a=0.5, b=0.1, c=0.1, d=0.1, e=0.05, f=0, g=0.05; or a=0.5, b=0.1, c=0.1, d=0.1, e=0, f=0.05, g=0.05.

[0013] The low-loss dielectric material of the above-mentioned under-filled tungsten bronze structure has adjustable dielectric constant at 25℃, and dielectric loss of 0.001-0.003. The temperature change rate of the material's capacitance satisfies |ΔC / C 25℃ The maximum temperature can reach 220℃, and the dielectric loss is lower than 0.05 until 400℃.

[0014] The low-loss dielectric material of the above-mentioned under-filled tungsten bronze structure is mechanically processed into the required size, then polished, and coated with electrodes and welded with leads to make ceramic capacitor elements.

[0015] The preparation method of the low-loss dielectric material of the above-mentioned under-filled tungsten bronze structure comprises the following steps:

[0016] (1) The Nb2O5 powder, B powder, C powder, D powder, La2O3 powder, Nd2O3 powder and G powder are weighed according to the structural general formula, mixed and uniformly ground to obtain a mixture; wherein the B powder is CaCO3 powder or CaO powder; the C powder is SrO powder or SrCO3 powder; the D powder is BaO powder or BaCO3 powder; and the G powder is Na2O powder or Na2CO3 powder;

[0017] (2) The mixture is pre-fired and finely ground to obtain a pre-fired powder;

[0018] (3) The binder is added to the pre-fired powder and granulated, and then pressed to obtain a green body;

[0019] (4) The green body is de-glued (to remove organic substances such as binders in the green body) and sintered, and then naturally cooled to room temperature to obtain a ceramic dielectric material with the general formula aNb2O5-bCaO-cSrO-dBaO-eLa2O3-fNd2O3-gNa2O.

[0020] The binder in step (3) is polyvinyl alcohol, and the amount added is 5wt% of the mass of the pre-fired powder.

[0021] Each of the above steps is carried out in an air atmosphere.

[0022] To ensure the material performance, the purity of each powder in step (1) is >99.0%.

[0023] The grinding and fine grinding in steps (1) and (2) are both wet ball milling methods, and the grinding balls can be iron balls, agate balls or zirconia balls, etc.

[0024] To improve the uniformity of the material, in step (1) grinding, the mass ratio of material:grinding ball:water (or alcohol) is 1:2-4:0.5-1, and the grinding time is 6-48 hours; in step (2) fine grinding, the mass ratio of pre-calcined powder:grinding ball:water (or alcohol) is 1:2-4:0.5-1, and the fine grinding time is 6-48 hours. After fine grinding, it is dried at 100-120℃ and passed through a 40-mesh sieve to obtain pre-calcined powder.

[0025] To further ensure the comprehensive performance of the material, in step (2), the heating rate of pre-firing is 3℃ / min, the temperature is 800℃, and the holding time is 3h; in step (4), the heating rate of debinding is 3℃ / min, the temperature is 800℃, and the time is 2h; the heating rate of sintering is 3℃ / min, the temperature is 1300℃, and the holding time is 3h.

[0026] To further ensure the strength and other properties of the material, the pressing pressure in step (3) above is 400-500 MPa.

[0027] The principle of this invention is as follows: This invention uses a mixture of raw materials in a certain molar ratio, and the dielectric constant of the resulting ceramic dielectric material can be adjusted by the proportional relationship between the raw materials; La and Nd elements are used to increase the dielectric constant of the dielectric system; and Ca and Na elements are introduced to reduce the dielectric loss of the material. The synergistic effect of multiple elements reduces the dielectric loss of the system.

[0028] Any techniques not mentioned in this invention are based on existing technologies.

[0029] Beneficial effects:

[0030] (1) The unfilled tungsten bronze structure low-loss dielectric material of the present invention has adjustable dielectric constant, low dielectric loss and small capacitance temperature change rate, and can be used in ceramic capacitors and MLCCs;

[0031] (2) The preparation method of the low-loss dielectric material of the unfilled tungsten bronze structure of the present invention can be carried out by sintering at medium and low temperature. It is environmentally friendly, simple in process, low in cost, and has good industrialization prospects. Attached Figure Description

[0032] Figure 1 The dielectric temperature spectrum of the ceramic dielectric materials in Examples 1-4 is shown, with a test frequency of 1 kHz.

[0033] Figure 2 The dielectric spectrum of the ceramic dielectric materials in Examples 1-4 is shown, and the test temperature is 25℃. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0035] The preparation method of 5wt% PVA in each example is as follows: take polyvinyl alcohol (polyvinyl alcohol 1750±50, purchased from Sinopharm Reagent) and add it to a beaker containing water (the mass ratio of polyvinyl alcohol to water is 5:95), stir and heat to 90℃, keep warm and stir until the polyvinyl alcohol is completely dissolved, then cool down to below 60℃ and continue stirring until it becomes a colloidal state, and naturally cool to room temperature to obtain polyvinyl alcohol.

[0036] In each example, the grinding balls consisted of agate balls with diameters of 3 mm (30%), 5 mm (50%), and 10 mm (20%).

[0037] Example 1

[0038] A method for preparing a ceramic dielectric material for capacitors, comprising the following steps:

[0039] (1) Nb2O5 powder, CaCO3 powder, SrCO3 powder, BaCO3 powder and La2O3 powder were weighed and mixed in a molar ratio of 0.50:0.125:0.125:0.125:0.0625, and ground evenly using a wet ball milling process. During grinding, the material:grinding ball:deionized water mass ratio was 1:2:1 and the mixture was ground for 24 hours. After grinding, the mixture was dried (to constant weight, the same for all other examples) and passed through a 40-mesh sieve to obtain the mixture. The purity of each raw material powder was >99.0%.

[0040] (2) The mixture is pre-calcined. The pre-calcination process is as follows: the temperature is raised to 800℃ at a rate of 3℃ / min and held for 3h to obtain pre-calcined powder.

[0041] (3) The pre-calcined powder in step (2) is first finely ground for 48 hours according to the mass ratio of material: grinding ball: deionized water = 1:2:0.8. After fine grinding, it is dried (to constant weight, the same for other examples) and passed through a 40-mesh sieve. Then, 5wt% PVA is added to the pre-calcined powder for granulation, and it is dry-pressed at 500MPa into a blank with a diameter of 10mm and a thickness of about 1mm.

[0042] (4) The green blank from step (3) is heated to 800℃ in a sintering furnace at a heating rate of 3℃ / min and held for 2 hours to remove organic matter from the green blank; the green blank is then sintered at a heating rate of 3℃ / min to 1300℃ and held for 3 hours, and then naturally cooled to room temperature to obtain a ceramic dielectric material. The general chemical formula of the ceramic dielectric material is aNb2O5-bCaO-cSrO-dBaO-eLa2O3, where a=0.5, b=0.125, c=0.125, d=0.125, and e=0.0625.

[0043] The surface of the sintered ceramic dielectric material was smoothed, cleaned, and dried. Silver paste was then screen-printed onto the material, dried again, and fired in an electric furnace at 600℃ for 30 minutes to obtain the ceramic capacitor. The dielectric temperature spectrum of the ceramic capacitor was tested, and the results are shown below. Figure 1 , Figure 2 The dielectric constant is very stable with changes in temperature and frequency. The dielectric properties of this ceramic capacitor at 1 kHz are shown in Table 1.

[0044] Temperature change rate | ΔC / C 25℃ The maximum temperature with a dielectric loss of ≤±15% is 210℃, and the dielectric loss is less than 0.05 at 400℃.

[0045] Example 2

[0046] A method for preparing a ceramic dielectric material for capacitors, comprising the following steps:

[0047] (1) Nb2O5 powder, CaCO3 powder, SrCO3 powder, BaCO3 powder and Nd2O3 powder were weighed and mixed in a molar ratio of 0.50:0.125:0.125:0.125:0.0625, and ground evenly by wet ball milling. During grinding, the material:grinding ball:deionized water mass ratio was 1:2:1 for 24 hours. After grinding, the mixture was dried and passed through a 40-mesh sieve to obtain the mixture. The purity of SrO powder, TiO2 powder, Bi2O3 powder, Fe2O3 powder and CaO powder was all >99.0%.

[0048] (2) The mixture is pre-calcined. The pre-calcination process is as follows: the temperature is raised to 800℃ at a rate of 3℃ / min and held for 3h to obtain pre-calcined powder.

[0049] (3) The pre-calcined powder in step (2) is first finely ground for 48 hours according to the mass ratio of material: grinding ball: deionized water = 1:2:0.8. After fine grinding, it is dried and passed through a 40-mesh sieve. Then, 5wt% PVA is added to the pre-calcined powder for granulation, and it is dry-pressed at 500MPa into a blank with a diameter of 10mm and a thickness of about 1mm.

[0050] (4) The green blank from step (3) is heated to 800℃ in a sintering furnace at a heating rate of 3℃ / min and held for 2 hours to remove organic matter from the green blank; the green blank is then sintered at a heating rate of 3℃ / min to 1200℃ and held for 3 hours, and then naturally cooled to room temperature to obtain a ceramic dielectric material. The general chemical formula of the ceramic dielectric material is aNb2O5-bCaO-cSrO-dBaO-fNd2O3, where a=0.5, b=0.125, c=0.125, d=0.125, and f=0.0625.

[0051] The surface of the sintered ceramic dielectric material was smoothed, cleaned, and dried. Silver paste was then screen-printed onto the material, dried again, and fired in an electric furnace at 600℃ for 30 minutes to obtain the ceramic capacitor. The dielectric temperature spectrum of the ceramic capacitor was tested, and the results are shown below. Figure 1 , Figure 2 The dielectric constant is very stable with changes in temperature and frequency. The dielectric properties of this ceramic capacitor at 1 kHz are shown in Table 1. Capacitance-temperature change rate |ΔC / C 25℃ The maximum temperature with a dielectric loss of ≤±15% is 200℃, and the dielectric loss is less than 0.05 at 400℃.

[0052] Example 3

[0053] A method for preparing a ceramic dielectric material for capacitors, comprising the following steps:

[0054] (1) Nb2O5 powder, CaCO3 powder, SrCO3 powder, BaCO3 powder, La2O3 powder and Na2CO3 powder were weighed and mixed in a molar ratio of 0.50:0.10:0.10:0.10:0.05:0.05, and ground evenly using a wet ball milling process. During grinding, the material:grinding ball:deionized water mass ratio was 1:2:1 for 24 hours. After grinding, the mixture was dried and passed through a 40-mesh sieve to obtain the mixture. The purity of each raw material powder was >99.0%.

[0055] (2) The mixture is pre-calcined. The pre-calcination process is as follows: the temperature is raised to 800℃ at a rate of 3℃ / min and held for 3h to obtain pre-calcined powder.

[0056] (3) The pre-calcined powder in step (2) is first finely ground for 48 hours according to the mass ratio of material: grinding ball: deionized water = 1:2:0.8. After fine grinding, it is dried and passed through a 40-mesh sieve. Then, 5wt% PVA is added to the pre-calcined powder for granulation, and it is dry-pressed at 500MPa into a blank with a diameter of 10mm and a thickness of about 1mm.

[0057] (4) The green blank from step (3) is heated to 800℃ in a sintering furnace at a heating rate of 3℃ / min and held for 2 hours to remove organic matter from the green blank; the green blank is then sintered at a heating rate of 3℃ / min to 1300℃ and held for 3 hours, and then naturally cooled to room temperature to obtain a ceramic dielectric material. The general chemical formula of the ceramic dielectric material is aNb2O5-bCaO-cSrO-dBaO-eLa2O3-gNa2O, where a=0.5, b=0.1, c=0.1, d=0.1, e=0.05, and g=0.05.

[0058] The surface of the sintered ceramic dielectric material was smoothed, cleaned, and dried. Silver paste was then screen-printed onto the material, dried again, and fired in an electric furnace at 600℃ for 30 minutes to obtain the ceramic capacitor. The dielectric temperature spectrum of the ceramic capacitor was tested, and the results are shown below. Figure 1 , Figure 2 The dielectric constant is very stable with changes in temperature and frequency. The dielectric properties of this ceramic capacitor at 1 kHz are shown in Table 1. Capacitance-temperature change rate |ΔC / C 25℃ The maximum temperature with a dielectric loss of ≤±15% is 220℃, and the maximum temperature with a dielectric loss of less than 0.05 is 330℃.

[0059] Example 4

[0060] A method for preparing a ceramic dielectric material for capacitors, comprising the following steps:

[0061] (1) Nb2O5 powder, CaCO3 powder, SrCO3 powder, BaCO3 powder, Nd2O3 powder and Na2CO3 powder were weighed and mixed in a molar ratio of 0.50:0.10:0.10:0.10:0.05:0.05, and ground evenly using a wet ball milling process. During grinding, the material:grinding ball:deionized water mass ratio was 1:2:1 for 24 hours. After grinding, the mixture was dried and passed through a 40-mesh sieve to obtain the mixture. Among them, the purity of SrO powder, TiO2 powder, Bi2O3 powder, Fe2O3 powder and CaO powder were all >99.0%.

[0062] (2) The mixture is pre-calcined. The pre-calcination process is as follows: the temperature is raised to 800℃ at a rate of 3℃ / min and held for 3h to obtain pre-calcined powder.

[0063] (3) The pre-calcined powder in step (2) is first finely ground for 48 hours according to the mass ratio of material: grinding ball: deionized water = 1:2:0.8. After fine grinding, it is dried and passed through a 40-mesh sieve. Then, 5wt% PVA is added to the pre-calcined powder for granulation, and it is dry-pressed at 500MPa into a blank with a diameter of 10mm and a thickness of about 1mm.

[0064] (4) The green blank from step (3) is heated to 800℃ in a sintering furnace at a heating rate of 3℃ / min and held for 2 hours to remove organic matter from the green blank; the green blank is then sintered at a heating rate of 3℃ / min to 1300℃ and held for 3 hours, and then naturally cooled to room temperature to obtain a ceramic dielectric material. The general chemical formula of the ceramic dielectric material is aNb2O5-bCaO-cSrO-dBaO-fNd2O3-gNa2O, where a=0.5, b=0.1, c=0.1, d=0.1, f=0.05, and g=0.05.

[0065] The surface of the sintered ceramic dielectric material was smoothed, cleaned, and dried. Silver paste was then screen-printed onto the material, dried again, and fired in an electric furnace at 600℃ for 30 minutes to obtain the ceramic capacitor. The dielectric temperature spectrum of the ceramic capacitor was tested, and the results are shown below. Figure 1 , Figure 2 The dielectric constant is very stable with changes in temperature and frequency. The dielectric properties of this ceramic capacitor at 1 kHz are shown in Table 1. Capacitance-temperature change rate |ΔC / C 25℃ The maximum temperature with a dielectric loss of ≤±15% is 117℃, and the maximum temperature with a dielectric loss of less than 0.05 is up to 350℃.

[0066] Table 1 shows the dielectric properties of the ceramic capacitors in Comparative Examples 1-2 and Examples 1-3 at 1 kHz.

[0067]

[0068]

[0069] As shown in Table 1, the ceramic capacitor dielectric materials prepared in Examples 1, 2, 3, and 4 exhibit good temperature stability, with a capacitance change rate |ΔC / C at very high temperatures. 25℃ |≤±15%, Examples 1, 2, and 3 meet the requirements of X9R, and Example 4 meets the requirements of X6R. X9R and X6R refer to the highest temperatures at which the volumetric temperature change rate is less than 15%, which are 200℃ and 105℃, respectively.

[0070] Comparative Example 1

[0071] A method for preparing a ceramic dielectric material for capacitors, comprising the following steps:

[0072] (1) Nb2O5 powder, PbO powder, SrCO3 powder, BaCO3 powder, La2O3 powder and Na2CO3 powder were weighed and mixed in a molar ratio of 0.50:0.10:0.10:0.10:0.05:0.05, and ground evenly using a wet ball milling process. During grinding, the material:grinding ball:deionized water mass ratio was 1:2:1 and the mixture was ground for 24 hours. After grinding, the mixture was dried and passed through a 40-mesh sieve to obtain the mixture. The purity of each raw material powder was >99.0%.

[0073] (2) The mixture is pre-calcined. The pre-calcination process is as follows: the temperature is raised to 800℃ at a rate of 3℃ / min and held for 3h to obtain pre-calcined powder.

[0074] (3) The pre-calcined powder in step (2) is first finely ground for 48 hours according to the mass ratio of material: grinding ball: deionized water = 1:2:0.8. After fine grinding, it is dried and passed through a 40-mesh sieve. Then, 5wt% PVA is added to the pre-calcined powder for granulation, and it is dry-pressed at 500MPa into a blank with a diameter of 10mm and a thickness of about 1mm.

[0075] (4) The green blank from step (3) is heated to 800℃ in a sintering furnace at a heating rate of 3℃ / min and held for 2 hours to remove organic matter from the green blank; sintering is then carried out at a heating rate of 3℃ / min to 1270℃ and held for 3 hours, and then naturally cooled to room temperature to obtain a ceramic dielectric material. The general chemical formula of the ceramic dielectric material is aNb2O5-bPbO-cSrO-dBaO-eLa2O3-gNa2O, where a=0.5, b=0.1, c=0.1, d=0.1, e=0.05, g=0.05, (Pb 0.2 Sr 0.2 Ba 0.2 La 0.2 Na 0.2 )Nb2O6.

[0076] The surface of the sintered ceramic dielectric material was smoothed, cleaned, and dried. Silver paste was then screen-printed onto the material, dried again, and fired in an electric furnace at 600℃ for 30 minutes to obtain the ceramic capacitor. The dielectric temperature spectrum of the ceramic capacitor was tested, and the results are shown below. Figure 1 , Figure 2 The dielectric constant is very stable with changes in temperature and frequency. The dielectric properties of this ceramic capacitor at 1 kHz are shown in Table 1. Capacitance-temperature change rate |ΔC / C 25℃ The maximum temperature with a dielectric loss of ≤±15% is 90℃, and the dielectric loss at room temperature is 0.008.

[0077] Comparative Example 2

[0078] A method for preparing a ceramic dielectric material for capacitors, comprising the following steps:

[0079] (1) Nb2O5 powder, SrCO3 powder, BaCO3 powder, La2O3 powder and Na2CO3 powder were weighed and mixed in a molar ratio of 0.50:0.125:0.125:0.0625:0.0625, and ground evenly using a wet ball milling process. During grinding, the material:grinding ball:deionized water mass ratio was 1:2:1 and the mixture was ground for 24 hours. After grinding, the mixture was dried and passed through a 40-mesh sieve to obtain the mixture. The purity of each raw material powder was >99.0%.

[0080] (2) The mixture is pre-calcined. The pre-calcination process is as follows: the temperature is raised to 800℃ at a rate of 3℃ / min and held for 3h to obtain pre-calcined powder.

[0081] (3) The pre-calcined powder in step (2) is first finely ground for 48 hours according to the mass ratio of material: grinding ball: deionized water = 1:2:0.8. After fine grinding, it is dried and passed through a 40-mesh sieve. Then, 5wt% PVA is added to the pre-calcined powder for granulation, and it is dry-pressed at 500MPa into a blank with a diameter of 10mm and a thickness of about 1mm.

[0082] (4) The green blank from step (3) is heated to 800℃ in a sintering furnace at a heating rate of 3℃ / min and held for 2 hours to remove organic matter from the green blank; the green blank is then sintered at a heating rate of 3℃ / min to 1300℃ and held for 3 hours, and then naturally cooled to room temperature to obtain a ceramic dielectric material. The general chemical formula of the ceramic dielectric material is aNb2O5-cSrO-dBaO-eLa2O3-gNa2O, where a=0.5, c=0.125, d=0.125, e=0.0625, and g=0.0625.

[0083] The surface of the sintered ceramic dielectric material was smoothed, cleaned, and dried. Silver paste was then screen-printed onto the material, dried again, and fired in an electric furnace at 600℃ for 30 minutes to obtain a ceramic capacitor. The dielectric temperature spectrum of the ceramic capacitor was tested, and its dielectric properties at 1kHz are shown in Table 1. Capacitive temperature change rate |ΔC / C 25℃ The maximum temperature with a dielectric loss of ≤±15% is 100℃, and the dielectric loss is 0.089.

[0084] Comparative Example 3

[0085] A method for preparing a ceramic dielectric material for capacitors, comprising the following steps:

[0086] (1) Nb2O5 powder, K2CO3 powder, SrCO3 powder, BaCO3 powder, La2O3 powder, Ag2O powder and Na2CO3 powder were weighed and mixed in a molar ratio of 0.50:0.05:0.10:0.10:0.05:0.05:0.05 and ground evenly using a wet ball milling process. During grinding, the material:grinding ball:deionized water mass ratio was 1:2:1 and the mixture was ground for 24 hours. After grinding, the mixture was dried and passed through a 40-mesh sieve to obtain the mixture. The purity of each raw material powder was >99.0%.

[0087] (2) The mixture is pre-calcined. The pre-calcination process is as follows: the temperature is raised to 800℃ at a rate of 3℃ / min and held for 3h to obtain pre-calcined powder.

[0088] (3) The pre-calcined powder in step (2) is first finely ground for 48 hours according to the mass ratio of material: grinding ball: deionized water = 1:2:0.8. After fine grinding, it is dried and passed through a 40-mesh sieve. Then, 5wt% PVA is added to the pre-calcined powder for granulation, and it is dry-pressed at 500MPa into a blank with a diameter of 10mm and a thickness of about 1mm.

[0089] (4) The green blank from step (3) is heated to 800℃ in a sintering furnace at a heating rate of 3℃ / min and held for 2 hours to remove organic matter from the green blank; sintering is then carried out at a heating rate of 3℃ / min to 1200℃ and held for 3 hours, and then naturally cooled to room temperature to obtain a ceramic dielectric material. The general chemical formula of the ceramic dielectric material is aNb2O5-bK2O-cSrO-dBaO-eLa2O3-fAg2O-gNa2O, where a=0.5, b=0.05, c=0.1, d=0.1, e=0.05, f=0.005, g=0.05, (Sr 0.5 Ba 0.5 K 0.5 La 0.5 Ag 0.5 Na 0.5 Nb5O 15 .

[0090] The surface of the sintered ceramic dielectric material was smoothed, cleaned, and dried. Silver paste was then screen-printed onto the surface and dried again. The material was then fired in an electric furnace at 600℃ for 30 minutes to obtain a ceramic capacitor. The dielectric temperature spectrum of the ceramic capacitor was tested, and its dielectric properties at 1kHz are shown in Table 1. (Temperature change rate |ΔC / C) 25℃ The maximum temperature with a dielectric loss of ≤±15% is 60℃, and the dielectric loss at room temperature is 0.056.

Claims

1. A low-loss dielectric material with an unfilled tungsten bronze structure, characterized in that: Its general structural formula is aNb2O5-bCaO-cSrO-dBaO-eLa2O3-fNd2O3-gNa2O, where a=0.5, b=0.125, c=0.125, d=0.125, e=0.0625, f=0, g=0; or a=0.5, b=0.125, c=0.125, d=0.125, e=0, f=0.0625, g=0; or a=0.5, b=0.1, c=0.1, d=0.1, e=0.05, f=0, g=0.05; or a=0.5, b=0.1, c=0.1, d=0.1, e=0, f=0.05, g=0.

05.

2. The low-loss dielectric material with an unfilled tungsten bronze structure according to claim 1, characterized in that: The dielectric loss at 25℃ is ≤0.

003.

3. A low-loss dielectric material with an unfilled tungsten bronze structure according to claim 1 or 2, characterized in that: Temperature change rate | ΔC / C 25℃ | ≤ ±15% of the maximum temperature ≥ 200℃.

4. The use of the low-loss dielectric material with an unfilled tungsten bronze structure as described in any one of claims 1-3, characterized in that: Used to manufacture ceramic capacitor elements.

5. A method for preparing an unfilled tungsten bronze structure low-loss dielectric material according to any one of claims 1-3, characterized in that: Includes the following steps: (1) Weigh Nb2O5 powder, B powder, C powder, D powder, La2O3 powder, Nd2O3 powder and G powder according to the general structural formula, mix and grind evenly to obtain a mixture; wherein, B powder is CaCO3 powder or CaO powder; C powder is SrO powder or SrCO3 powder; D powder is BaO powder or BaCO3 powder; G powder is Na2O powder or Na2CO3 powder; (2) The mixture is pre-calcined and then finely ground to obtain pre-calcined powder; (3) Add the binder to the pre-fired powder and granulate it, then press it to form a green blank; (4) After removing the binder, the green blank is sintered and naturally cooled to room temperature to obtain a ceramic dielectric material with the general formula aNb2O5-bCaO-cSrO-dBaO-eLa2O3-fNd2O3-gNa2O.

6. The preparation method according to claim 5, characterized in that: The purity of each powder in step (1) is >99.0%.

7. The preparation method according to claim 5 or 6, characterized in that: The grinding and fine grinding in steps (1) and (2) are both done using wet ball milling. In step (1) grinding, the mass ratio of material: grinding ball: water or alcohol is 1:2~4:0.5~1, and the grinding time is 6~48 hours. In step (2) fine grinding, the mass ratio of pre-calcined powder: grinding ball: water or alcohol is 1:2~4:0.5~1, and the fine grinding time is 6~48 hours. After fine grinding, the powder is dried at 100~120℃ and passed through a 40-mesh sieve to obtain pre-calcined powder.

8. The preparation method according to claim 5 or 6, characterized in that: In step (2), the heating rate of pre-firing is 3℃ / minute, the temperature is 800℃, and the holding time is 3h; in step (4), the heating rate of debinding is 3℃ / minute, the temperature is 800℃, and the time is 2h; the heating rate of sintering is 3℃ / minute, the temperature is 1300℃, and the holding time is 3h.

9. The preparation method according to claim 5 or 6, characterized in that: In step (3), the pressing pressure is 400~500MPa.

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