Glass-coated strontium titanate-based giant dielectric ceramic material and method for preparing the same

Abstract

This invention relates to the field of dielectric ceramics technology, providing a glass-coated strontium titanate-based giant dielectric ceramic material and its preparation method. This invention utilizes a zinc borosilicate glass sol to coat strontium titanate-based ceramic powder, followed by pressing, aging, pulverizing, molding, debinding, and sintering to obtain the glass-coated strontium titanate-based giant dielectric ceramic material. This invention allows the glass sol to be uniformly distributed on the surface of the ceramic powder, forming a glass sol coating layer with a nanometer-thickness. After melting, the coating layer has almost no large pores, effectively improving the performance of the strontium titanate-based ceramic material. The glass-coated strontium titanate-based giant dielectric ceramic material prepared by this invention has a stable structure and good thermal stability, exhibiting a stable high dielectric constant and low dielectric loss over a wide temperature range, and can be widely used in the field of energy storage electronic materials.

Description

Technical Field

[0001] This invention relates to the field of dielectric ceramics technology, and in particular to a glass-coated strontium titanate-based giant dielectric ceramic material and its preparation method. Background Technology

[0002] Giant dielectric ceramics are ceramic capacitor materials with high energy storage performance, characterized by high power density, high dielectric constant, and low dielectric loss, making them a promising material for the miniaturization and micro-miniaturization of energy storage devices. Common substrate materials for giant dielectric ceramics include CaCu3Ti4O. 12 NiO, BaTiO3, TiO2 and SrTiO3, of which CaCu3Ti4O 12 While NiO exhibits a high dielectric constant, it also suffers from high dielectric loss. BaTiO3, due to its relaxor ferroelectric properties, undergoes a ferroelectric phase transition at the Curie temperature, limiting its application to a specific temperature range. TiO2, despite its high dielectric constant and low dielectric loss, suffers from low breakdown strength, significantly restricting its application environment. SrTiO3 possesses low dielectric loss, high breakdown strength, and wide frequency / temperature stability, but its dielectric constant in practical applications is only 300, failing to meet real-world requirements. Therefore, developing SrTiO3-based giant dielectric ceramics with superior overall performance is of significant research importance. Previous studies have yielded rare-earth-doped strontium titanate-based giant dielectric ceramics with high dielectric constant and low dielectric loss by doping SrTiO3, but these materials still suffer from poor dielectric thermal stability. Improving the overall thermal stability of ceramic samples is a pressing technical challenge in this field.

[0003] Zinc borosilicate glass (ZnO-B2O3-SiO2 glass) has extremely low dielectric loss of ~10. -3 It possesses excellent insulation properties and chemical stability. Introducing it into strontium titanate ceramics can enhance the grain boundary barrier at the ceramic interface, thereby improving the insulation performance and thermal stability of the ceramic sample. Traditional methods typically employ a melt-synthesizing process to synthesize glass powder, which is then ball-milled and mixed with ceramic powder before sintering. This method struggles to control the bonding between the glass and ceramic, leaving pores after sintering due to partial aggregation of glass powder. The presence of these pores not only further increases the dielectric loss of the material but also reduces its thermal stability, leading to accelerated performance degradation at high temperatures and failing to meet the stringent requirements of high-end electronic devices. Summary of the Invention

[0004] In view of this, the present invention provides a glass-coated strontium titanate-based giant dielectric ceramic material and its preparation method. The glass coating layer of the glass-coated strontium titanate-based giant dielectric ceramic material prepared by the present invention has almost no large pores, and it exhibits a stable high dielectric constant and low dielectric loss over a wide temperature range, which can be widely used in the field of energy storage electronic materials.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A method for preparing a glass-coated strontium titanate-based giant dielectric ceramic material includes the following steps: Strontium titanate-based ceramic powder dispersion was mixed with zinc borosilicate glass sol for coating, resulting in zinc borosilicate glass sol-coated strontium titanate-based ceramic powder; the chemical formula of the strontium titanate-based ceramic powder is shown in Formula I: Sr 0.985 Lu 0.01 Ti 1-x Ta x O3 formula I; In Equation I: x is 0.005~0.02; The zinc borosilicate glass sol-coated strontium titanate ceramic powder, binder and water are mixed and then pressed, aged, crushed and shaped in sequence to obtain a ceramic green body; The ceramic preform is debinded and then sintered to obtain glass-coated strontium titanate-based giant dielectric ceramic material; the sintering atmosphere is nitrogen.

[0006] Preferably, the preparation method of the strontium titanate-based ceramic powder includes: mixing strontium carbonate, titanium dioxide, lutetium oxide and tantalum pentoxide to obtain raw material powder; pre-synthesizing the raw material powder by ball milling once, and then ball milling and sieving a second time to obtain the strontium titanate-based ceramic powder.

[0007] Preferably, the pre-synthesis temperature is 1150~1250℃, the holding time is 3~5h, and the heating rate to the pre-synthesis temperature is 4~6℃ / min.

[0008] Preferably, the preparation method of the zinc borosilicate glass sol includes: dissolving zinc nitrate and boric acid in water under acidic conditions to obtain zinc borosilicate sol; hydrolyzing silicate ester in ethanol to obtain silica sol; and mixing the silica sol and zinc borosilicate sol to react and obtain zinc borosilicate glass sol.

[0009] Preferably, based on the total molar amount of ZnO, B2O3 and SiO2 as 100%, the molar fraction of zinc nitrate is 35-55%, the molar fraction of boric acid is 10-25%, and the molar fraction of silicate ester is 35-50%.

[0010] Preferably, the mass ratio of zinc borosilicate glass in the zinc borosilicate glass sol to strontium titanate-based ceramic powder in the strontium titanate-based ceramic powder dispersion is 0.5~1:1; and the coating time is 0.5~2h.

[0011] Preferably, in the zinc borosilicate glass sol-coated strontium titanate-based ceramic powder, the thickness of the zinc borosilicate glass sol coating layer is 3~10 nm.

[0012] Preferably, the binder is a polyvinyl alcohol solution, and the amount of the binder is 1-2% of the mass of the strontium titanate ceramic powder coated with the zinc borosilicate glass sol; the amount of water is 0.5-1% of the mass of the strontium titanate ceramic powder coated with the zinc borosilicate glass sol.

[0013] Preferably, the temperature for discharging the adhesive is 550~650℃ and the holding time is 1.5~2.5h; the temperature for sintering is 1400~1500℃ and the holding time is 3~5h.

[0014] The present invention also provides a glass-coated strontium titanate-based giant dielectric ceramic material prepared by the preparation method described above, comprising strontium titanate-based ceramic material and zinc borosilicate glass coated on the surface of the strontium titanate-based ceramic material.

[0015] This invention provides a method for preparing glass-coated strontium titanate-based giant dielectric ceramic material, comprising the following steps: mixing a strontium titanate-based ceramic powder dispersion with a zinc borosilicate glass sol for coating, thereby obtaining zinc borosilicate glass sol-coated strontium titanate-based ceramic powder; the chemical formula of the strontium titanate-based ceramic powder is shown in Formula I; the zinc borosilicate glass sol-coated strontium titanate-based ceramic powder, a binder, and water are mixed and then sequentially pressed, aged, pulverized, and shaped to obtain a ceramic green body; the ceramic green body is debinded and then sintered to obtain glass-coated strontium titanate-based giant dielectric ceramic material, wherein the sintering atmosphere is nitrogen. This invention uses zinc borosilicate glass sol to coat strontium titanate-based ceramic powder, which allows the glass to be uniformly distributed on the surface of the ceramic powder, forming a glass coating layer with a nanometer-thickness. After melting, the glass coating layer has almost no large pores, thus effectively improving the performance of the strontium titanate-based ceramic material. The glass-coated strontium titanate-based giant dielectric ceramic material prepared by this invention exhibits stable structure and good thermal stability, possessing a consistently high dielectric constant and low dielectric loss over a wide temperature range, making it widely applicable in the field of energy storage electronic materials. Furthermore, this invention allows for adjustment of the coating layer thickness by regulating the coating time, thereby controlling the glass content in the final giant dielectric ceramic material. Additionally, the zinc borosilicate glass, used as a sintering aid, can lower the sintering temperature of the ceramic powder. Moreover, this invention employs a sol-gel method to hydrolyze multi-metal alkoxides, followed by a condensation reaction to form a zinc borosilicate glass sol. The prepared glass sol possesses high purity and uniformity, further ensuring the performance of the final ceramic material.

[0016] The results of the examples show that the glass-coated strontium titanate-based giant dielectric ceramic material prepared by the present invention has a dielectric constant of ~185663 and a dielectric loss of ~0.0257 under the test conditions of room temperature and 1 kHz. The dielectric constant change rate does not exceed 15% in the temperature range of 1 kHz and 25~300℃. Attached Figure Description

[0017] Figure 1 XRD patterns of ZnO-B2O3-SiO2 glass powder at different sintering temperatures; Figure 2 Sr-coated ZnO-B2O3-SiO2 glass at different coating times 0.985 Lu 0.01 Ti 0.985 Ta 0.015 XRD pattern of O3 ceramics; Figure 3 Sr-coated ZnO-B2O3-SiO2 glass at different coating times 0.985 Lu 0.01 Ti 0.985 Ta 0.015 Transmission electron microscopy images of O3 ceramics, where: (a)~(c) uncoated, (d)~(f) coated for 0.5h, (g)~(i) coated for 1h, (j)~(l) coated for 2h; Figure 4 The ZnO-B2O3-SiO2 glass-coated Sr prepared in Example 2 0.985 Lu 0.01 Ti 0.985 Ta 0.015 EDS energy dispersive spectroscopy of O3 ceramics; Figure 5 Sr-coated ZnO-B2O3-SiO2 glass at different coating times 0.985 Lu 0.01 Ti 0.985 Ta 0.015 The graph shows the dielectric properties of O3 ceramics as a function of temperature, where: (a) dielectric constant, (b) dielectric loss, and (c) rate of change of dielectric constant. Detailed Implementation

[0018] This invention provides a method for preparing a glass-coated strontium titanate-based giant dielectric ceramic material, comprising the following steps: Strontium titanate-based ceramic powder dispersion was mixed with zinc borosilicate glass sol for coating, resulting in zinc borosilicate glass sol-coated strontium titanate-based ceramic powder; the chemical formula of the strontium titanate-based ceramic powder is shown in Formula I: Sr 0.985 Lu0.01 Ti 1-x Ta x O3 formula I; In Equation I: x is 0.005~0.02; The zinc borosilicate glass sol-coated strontium titanate ceramic powder, binder and water are mixed and then pressed, aged, crushed and shaped in sequence to obtain a ceramic green body; The ceramic preform is debinded and then sintered to obtain a glass-coated strontium titanate-based giant dielectric ceramic material. The sintering atmosphere is nitrogen.

[0019] This invention involves coating a strontium titanate-based ceramic powder dispersion with a zinc borosilicate glass sol to obtain strontium titanate-based ceramic powder coated with a zinc borosilicate glass sol. In this invention, the chemical formula of the strontium titanate-based ceramic powder is shown in Formula I, where x is preferably 0.005, 0.001, or 0.015. In a specific embodiment of this invention, the strontium titanate-based ceramic powder is preferably Sr... 0.985 Lu 0.01 Ti 0.985 Ta 0.015 O3; the strontium titanate-based ceramic powder is preferably prepared by solid-state synthesis.

[0020] In this invention, the preferred method for preparing the strontium titanate-based ceramic powder includes: mixing strontium carbonate, titanium dioxide, lutetium oxide and tantalum pentoxide to obtain raw material powder; pre-synthesizing the raw material powder by ball milling once, and then ball milling and sieving a second time to obtain the strontium titanate-based ceramic powder.

[0021] In this invention, the conditions for the primary and secondary ball milling independently include: the milling balls are zirconia balls, the dispersion medium is deionized water, the preferred mass ratio of the raw material powder, zirconia balls, and deionized water is 1:5:1.5, the milling speed is 300~450 rpm, and the milling time is 7~9 h; the primary ball milling preferably involves drying the resulting milled material, the preferred drying temperature is 70~90℃, and the preferred drying time is 20~24 h; the preferred pre-synthesis temperature is 1150~1250℃. Specifically, the temperature can be 1200℃, the holding time is preferably 3~5h, specifically 4h, the heating rate to the pre-synthesis temperature is preferably 4~6℃ / min, specifically 5℃ / min; the pre-synthesis atmosphere is preferably air; the pre-synthesis is preferably carried out in a muffle furnace; after the secondary ball milling, the obtained ball milling material is preferably dried and then sieved, the drying temperature is preferably 70~90℃, the drying time is preferably 20~24h, and the mesh size of the sieve used for sieving is preferably 500 mesh.

[0022] In this invention, the solvent for the strontium titanate-based ceramic powder dispersion is preferably ethanol; preferably, the strontium titanate-based ceramic powder is added to ethanol and ultrasonicated to obtain the strontium titanate-based ceramic powder dispersion, and the ultrasonication time is preferably 0.5 h.

[0023] In this invention, the zinc borosilicate glass sol (denoted as ZnO-B2O3-SiO2 glass sol) is preferably synthesized by the sol-gel method; specifically, the preparation method of the zinc borosilicate glass sol preferably includes: dissolving zinc nitrate and boric acid in water under acidic conditions to obtain zinc borosilicate sol; hydrolyzing silicate ester in ethanol to obtain silica sol; and mixing the silica sol and zinc borosilicate sol for reaction to obtain zinc borosilicate glass sol.

[0024] In this invention, the total molar amount of ZnO, B2O3, and SiO2 is 100% (i.e., the molar amount of zinc nitrate is calculated as ZnO, the molar amount of boric acid is calculated as B2O3, and the molar amount of silicate ester is calculated as SiO2). The molar fraction of zinc nitrate is 35-55%, preferably 45-50%, the molar fraction of boric acid is 10-25%, preferably 12-20%, and the molar fraction of silicate ester is 35-50%, preferably 36-48%. The water used in this invention is preferably deionized water. The acidic conditions are preferably provided by acetic acid, and the pH value of the acidic conditions is preferably 4-6. In specific embodiments of this invention, the molar ratio of acetic acid to water can be controlled at 0.05-0.1:1. The preferred ratio of zinc nitrate to water is 1g:10-20mL. The preferred dissolution temperature is 30-50℃, specifically 40℃, and the preferred dissolution time is 0.5-1h. Zinc nitrate and boric acid dissolve and dissociate under acidic conditions to obtain a homogeneous and stable zinc-boron precursor solution.

[0025] In this invention, the silicate ester is preferably tetraethyl orthosilicate; the molar ratio of ethanol to silicate ester is preferably 5 to 25:1, specifically 5:1, 9:1, 10:1, 15:1, 19:1 or 25:1; the hydrolysis temperature is preferably room temperature, and the hydrolysis time is preferably 0.5 to 1 hour.

[0026] In this invention, the silica sol is preferably added dropwise to the zinc borosilicate sol. The reaction temperature is preferably 30-50°C, specifically 40°C. This invention does not have specific requirements for the reaction time; thorough stirring is sufficient until a transparent zinc borosilicate glass sol is obtained. In a specific embodiment of this invention, the reaction time can be 1-3 hours. During the reaction, the silica sol is uniformly mixed with the zinc borosilicate sol in the liquid phase and undergoes hydrolysis and condensation chemical reactions to form a stable ternary sol system in the solution. The sol undergoes slow polymerization between the colloid particles after aging, forming a gel with a three-dimensional network structure.

[0027] In this invention, the preferred mass ratio of zinc borosilicate glass in the zinc borosilicate glass sol to strontium titanate-based ceramic powder in the strontium titanate-based ceramic powder dispersion is 0.5 to 1:1, specifically 0.5:1, 0.66:1, 0.8:1, or 1:1; the preferred coating time is 0.5 to 2 hours, specifically 0.5, 1, or 2 hours; the mixing is preferably carried out under stirring conditions. During the mixing process, the zinc borosilicate glass sol adsorbs onto the surface of the strontium titanate-based ceramic powder under electrostatic action, thereby completing the coating; this invention can control the thickness of the zinc borosilicate glass coating layer by controlling the mixing time, thereby controlling the glass content in the final giant dielectric ceramic material.

[0028] In this invention, the zinc borosilicate glass sol-coated strontium titanate-based ceramic powder specifically includes strontium titanate-based ceramic powder and a zinc borosilicate glass sol coating layer covering the surface of the strontium titanate-based ceramic powder. The thickness of the zinc borosilicate glass sol coating layer is preferably 3~10 nm.

[0029] After obtaining the zinc borosilicate glass sol-coated strontium titanate-based ceramic powder, the present invention mixes the zinc borosilicate glass sol-coated strontium titanate-based ceramic powder, a binder, and water, and then sequentially presses, ages, pulverizes, and shapes the mixture to obtain a ceramic green body. In this invention, the binder is preferably a polyvinyl alcohol solution, the concentration of which is preferably 3-5 wt%, specifically 4 wt%, and the solvent of which is water. The amount of binder is preferably 1-2% of the mass of the zinc borosilicate glass sol-coated strontium titanate ceramic powder; the amount of water is 0.5-1% of the mass of the zinc borosilicate glass sol-coated strontium titanate ceramic powder. In this invention, strontium titanate-based ceramic powder coated with zinc borosilicate glass sol, a binder, and water are mixed, ground, and then pressed. The pressed green body is preferably cylindrical. The aging time is preferably 20-30 hours, specifically 24 hours, and the aging is preferably carried out under static conditions. The pulverization is preferably sieved to obtain granular powder, and the mesh size of the sieve is preferably 40 mesh. The forming is preferably dry pressing, specifically dry pressing under unidirectional pressure. The unidirectional pressure of the dry pressing is preferably 10-20 MPa, specifically 10, 15, or 20 MPa. The ceramic green body is preferably cylindrical. In a specific embodiment of this invention, the diameter of the ceramic green body is preferably 10 mm, and the thickness is preferably 1.5-2.5 mm.

[0030] After obtaining the ceramic green body, the present invention removes the binder from the ceramic green body and then sintersects it to obtain a glass-coated strontium titanate-based giant dielectric ceramic material. In the present invention, the binder removal temperature is preferably 550~650℃, specifically 550℃, 600℃ or 650℃, and the holding time is preferably 1.5~2.5h, specifically 1.5, 2 or 2.5h.

[0031] In this invention, the sintering temperature is preferably 1400~1500℃, specifically 1400, 1425, 1440, 1450, 1460 or 1500℃, the holding time is preferably 3~5h, specifically 3, 3.5, 4, 4.5 or 5h, and the sintering atmosphere is preferably nitrogen.

[0032] In this invention, the preferred heating procedure for reaching the sintering temperature is as follows: heating to 1200°C at a rate of 4-6°C / min, then heating to 1400°C at a rate of 2-4°C / min, and then heating to the sintering temperature at a rate of 1-3°C / min; when the sintering temperature is 1400°C, the last heating step can be omitted.

[0033] In this invention, after the sintering heat preservation process is completed, it is preferable to cool down. The cooling is preferably carried out by first cooling down to 500°C at a rate of 4~6°C / min, and then cooling down to room temperature with the furnace.

[0034] This invention also provides a glass-coated strontium titanate-based giant dielectric ceramic material prepared by the preparation method described above, comprising a strontium titanate-based ceramic material and zinc borosilicate glass coated on the surface of the strontium titanate-based ceramic material, wherein the chemical formula of the strontium titanate-based ceramic material is shown in Formula I, preferably Sr 0.985 Lu 0.01 Ti 0.985 Ta 0.015 O3, the zinc borosilicate glass is specifically ZnO-B2O3-SiO2 glass, wherein the molar ratio of ZnO, B2O3 and SiO2 is preferably 35~55:10~25:35~50.

[0035] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0036] Comparative Example 1 Preparation of Sr 0.985 Lu 0.01 Ti 0.985 Ta 0.015 The specific preparation steps for O3 ceramic materials are as follows: Step 1: Using strontium carbonate, titanium dioxide, lutetium oxide, and tantalum pentoxide as raw materials, according to the chemical formula Sr 0.985 Lu 0.01 Ti 0.985 Ta 0.015O3 was used as the raw material, and the resulting raw material powder was ball-milled and dried once to obtain a raw material mixture. This mixture was then placed in a muffle furnace for pre-synthesis in an air atmosphere, followed by a second ball milling, passing through a 500-mesh sieve, and drying to produce Sr. 0.985 Lu 0.01 Ti 0.985 Ta 0.015 O3 ceramic powder; wherein, the conditions for primary and secondary ball milling are as follows: the milling balls are zirconia balls, the milling medium is deionized water, and the mass ratio of raw material powder, zirconia balls and deionized water is 1:5:1.5; the milling speed is 400 rpm and the milling time is 8h; the pre-synthesis temperature is 1200℃, the holding time is 4h, and the heating rate is 5℃ / min.

[0037] Step 2: The ceramic powder prepared in Step 1 is mixed with 4wt% polyvinyl alcohol solution (1% of the ceramic powder mass) and deionized water (0.5% of the ceramic powder mass) and ground. After grinding, it is pressed into a cylindrical shape, left to stand for aging for 24 hours, then crushed and passed through a 40-mesh sieve to obtain granular powder. It is then dry-pressed under unidirectional pressure of 15 MPa. The resulting ceramic blank has a diameter of 10 mm and a thickness of 2 mm. Step 3: Place the ceramic blank pressed in Step 2 into a muffle furnace for air atmosphere debinding. The debinding temperature is 600℃ and the holding time is 2h to obtain the ceramic sample. Step 4: Place the ceramic sample synthesized in Step 3 into an alumina crucible, and then place the crucible into a tube furnace for sintering under a nitrogen atmosphere. The sintering program is as follows: heat to 1200℃ at a rate of 5℃ / min, then heat to 1400℃ at a rate of 3℃ / min, then heat to 1450℃ at a rate of 2℃ / min, and hold at this temperature for 4 hours. After holding, cool to 500℃ at a rate of 5℃ / min, and then cool to room temperature with the furnace to obtain Sr. 0.985 Lu 0.01 Ti 0.985 Ta 0.015 O3 giant dielectric ceramic sheet.

[0038] The sintered ceramic sheet was polished on both sides and coated with silver electrodes. It was then placed in a muffle furnace and heated to 550℃ for 15 minutes to burn the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. The test results showed that at room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~153991, and the dielectric loss was ~0.0191. Within a temperature range of 1 kHz and 25–94℃, the rate of change of the dielectric constant did not exceed 15%.

[0039] Example 1 Preparation of ZnO-B2O3-SiO2 glass-coated Sr 0.985Lu 0.01 Ti 0.985 Ta 0.015 The specific preparation steps for O3 ceramic materials are as follows: Step 1: Prepare strontium titanate ceramics using a solid-state synthesis method, using strontium carbonate, titanium dioxide, lutetium oxide, and tantalum pentoxide as raw materials, according to the chemical formula Sr 0.985 Lu 0.01 Ti 0.985 Ta 0.015 O3 was used as the raw material, and the resulting raw material powder was ball-milled and dried once to obtain a raw material mixture. This mixture was then placed in a muffle furnace for pre-synthesis in an air atmosphere, followed by a second ball milling, passing through a 500-mesh sieve, and drying to produce Sr. 0.985 Lu 0.01 Ti 0.985 Ta 0.015 O3 ceramic powder; the conditions for primary ball milling, secondary ball milling and pre-synthesis were the same as those for Comparative Example 1; Step 2: Synthesize ZnO-B₂O₃-SiO₂ glass sol using the sol-gel method, with tetraethyl orthosilicate, zinc nitrate, and boric acid as raw materials. The content of each component in the material is: ZnO: 43 mol%, B₂O₃: 15 mol%, SiO₂: 42 mol%; The specific preparation steps of ZnO-B₂O₃-SiO₂ glass sol are as follows: (1) Weigh 5.4488g of zinc nitrate hexahydrate and 0.7861g of boric acid according to the proportion and dissolve them in 70mL of deionized water under acidic conditions. Stir at 40℃ for 0.5 hours to ensure that the raw materials are fully dissolved in the deionized water. The acidic conditions are provided by acetic acid, and the molar ratio of acetic acid to deionized water is controlled at 0.05:1. (2) Weigh 3.7651g of tetraethyl orthosilicate and dissolve it in 20mL of ethanol. Stir at room temperature for 0.5 hours to allow the tetraethyl orthosilicate to be fully hydrolyzed. (3) The silicon source hydrolysate prepared in step (2) is added dropwise to the zinc boron sol prepared in (1), and stirred thoroughly at 40°C until a transparent ZnO-B2O3-SiO2 glass sol is obtained.

[0040] Step 3: Weigh 15g of the ceramic powder prepared in Step 1 and place it in a beaker. Add ethanol and sonicate for 0.5 hours to uniformly disperse the ceramic powder in the ethanol. Then, add the ZnO-B2O3-SiO2 glass sol prepared in Step 2 dropwise to the ceramic powder dispersion and stir for 0.5 hours. The total mass ratio of zinc borosilicate glass in the added glass sol to the mass of ceramic powder is 0.66:1. This yields Sr coated with ZnO-B2O3-SiO2 glass sol. 0.985 Lu 0.01 Ti 0.985 Ta 0.015 O3 ceramic powder.

[0041] Step 4: Mix the ceramic powder prepared in Step 3 with 4wt% polyvinyl alcohol solution (1% of the ceramic powder mass) and deionized water (0.5% of the ceramic powder mass) and grind it. After grinding, press it into a cylindrical shape, let it stand for aging for 24 hours, then crush it and pass it through a 40-mesh sieve to obtain granular powder. Dry press it under unidirectional pressure. The dry pressing conditions are the same as those in Comparative Example 1. Step 5: Place the ceramic blank pressed in Step 4 into a muffle furnace for air atmosphere debinding. The debinding temperature is 600℃ and the holding time is 2h to obtain the ceramic sample. Step Six: Place the ceramic sample synthesized in Step Five into an alumina crucible, and then place the crucible into a tube furnace for sintering. The sintering procedure is the same as that of Comparative Example 1, thus obtaining ZnO-B2O3-SiO2 glass-coated Sr. 0.985 Lu 0.01 Ti 0.985 Ta 0.015 O3 giant dielectric ceramic sheet.

[0042] The sintered ceramic sheet was polished on both sides and coated with silver electrodes. It was then placed in a muffle furnace and heated to 550℃ for 15 minutes to burn the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~181178, and the dielectric loss was ~0.0361. The rate of change of the dielectric constant within the temperature range of 1 kHz and 25~200℃ did not exceed 15%.

[0043] Example 2 Preparation of ZnO-B2O3-SiO2 glass-coated Sr 0.985 Lu 0.01 Ti 0.985 Ta 0.015 The O3 ceramic material is prepared using the same steps as in Example 1, except that the stirring time for adding the glass sol dropwise into the ceramic powder dispersion in step three of Example 1 is changed from 0.5h to 1h.

[0044] The sintered ceramic sheet was polished on both sides and coated with silver electrodes. It was then placed in a muffle furnace and heated to 550℃ for 15 minutes to burn the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~185663, and the dielectric loss was ~0.0257. The rate of change of the dielectric constant within the temperature range of 1 kHz and 25~300℃ did not exceed 15%.

[0045] Example 3 Preparation of ZnO-B2O3-SiO2 glass-coated Sr 0.985 Lu 0.01 Ti0.985 Ta 0.015 The O3 ceramic material is prepared using the same steps as in Example 1, except that the stirring time for adding the transparent glass sol dropwise into the ceramic powder suspension in step three of Example 1 is changed from 0.5h to 2h.

[0046] The sintered ceramic sheet was polished on both sides and coated with silver electrodes. It was then placed in a muffle furnace and heated to 550℃ for 15 minutes to burn the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~188454, and the dielectric loss was ~0.0306. The rate of change of the dielectric constant within the temperature range of 1 kHz and 25~300℃ did not exceed 15%.

[0047] Example 4 Preparation of ZnO-B2O3-SiO2 glass-coated Sr 0.985 Lu 0.01 Ti 0.985 Ta 0.015 The O3 ceramic material is prepared using the same steps as in Example 2, except that the sintering temperature is changed from 1450℃ to 1440℃.

[0048] The sintered ceramic sheet was polished on both sides and coated with silver electrodes. It was then placed in a muffle furnace and heated to 550℃ for 15 minutes to burn the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~134930, and the dielectric loss was ~0.0336. The rate of change of the dielectric constant within the temperature range of 1 kHz and 25~300℃ did not exceed 15%.

[0049] Example 5 Preparation of ZnO-B2O3-SiO2 glass-coated Sr 0.985 Lu 0.01 Ti 0.985 Ta 0.015 The O3 ceramic material is prepared using the same steps as in Example 2, except that the sintering temperature is changed from 1450℃ to 1460℃.

[0050] The sintered ceramic sheet was polished on both sides and coated with silver electrodes. It was then placed in a muffle furnace and heated to 550℃ for 15 minutes to burn the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~184135, and the dielectric loss was ~0.1247. The rate of change of the dielectric constant within the temperature range of 1 kHz and 25~300℃ did not exceed 15%.

[0051] Comparative Example 2 Preparation of ZnO-B2O3-SiO2 glass-coated Sr0.985 Lu 0.01 Ti 0.985 Ta 0.015 The O3 ceramic material is prepared using the same steps as in Example 2, except that the sintering atmosphere is changed from nitrogen to air.

[0052] The sintered ceramic sheet was polished on both sides and coated with silver electrodes. It was then placed in a muffle furnace and heated to 550℃ for 15 minutes to burn the electrodes. Dielectric properties were tested using an Agilent 4294A impedance analyzer. At room temperature and a test frequency of 1 kHz, the dielectric constant of the ceramic material was ~712, and the dielectric loss was ~0.0590. The rate of change of the dielectric constant did not exceed 15% within the temperature range of 25~300℃ at 1 kHz.

[0053] Performance testing: 1. Dielectric property testing The dielectric properties of the ceramic samples prepared in Examples 1-6 and Comparative Example 1 are summarized in the table below.

[0054] Table 1. Dielectric properties of ceramic samples prepared in Examples 1-6 and Comparative Example 1

[0055] 2. XRD Testing The ZnO-B2O3-SiO2 glass sols obtained in Comparative Examples 1-2 and Examples 1-5 were allowed to stand at room temperature for 24 hours and then dried. The resulting dry gels were sintered at different temperatures (sintering temperatures of 500, 600, 700, and 900°C, and sintering time of 1 hour) to obtain ZnO-B2O3-SiO2 glass powder.

[0056] XRD patterns of ZnO-B2O3-SiO2 glass powders obtained at different sintering temperatures are shown below. Figure 1 As shown, it can be seen that no obvious sharp diffraction peaks were formed when the glass sample was sintered at 500℃, and the glass powder was in a glassy state; when sintered at 600, 700 and 900℃, Zn2SiO4 and Zn3(BO3)2 phases were generated, and the glass crystals were precipitated.

[0057] Sr obtained from ZnO-B2O3-SiO2 glass coating at different coating times 0.985 Lu 0.01 Ti 0.985 Ta 0.015 The XRD pattern of O3 ceramics is shown below. Figure 2 As shown, Figure 2 In the diagram, T=0 represents the sample prepared in Comparative Example 1, T=0.5h represents the sample prepared in Example 1, T=1h represents the sample prepared in Example 2, and T=2h represents the sample prepared in Example 3. Figure 2As can be seen, the diffraction peaks did not change significantly with the extension of coating time, and the ceramic powder exhibited a cubic perovskite structure. All diffraction peaks could be matched with SrTiO3 (PDF# 84-0444). The coated powder still maintained the original crystal structure of the ceramic, and no diffraction peaks of Zn2O3-B2O3-SiO2 glass, Zn2SiO4, and Zn3(BO3)2 phases were detected. This is because the ZnO-B2O3-SiO2 glass powder is in a glassy state and no sharp diffraction peaks are formed (the zinc borosilicate glass content is low, and the glass coating layer has little effect on the phase composition of the ceramic powder).

[0058] 3. Morphological testing Figure 3 Sr-coated ZnO-B2O3-SiO2 glass at different coating times 0.985 Lu 0.01 Ti 0.985 Ta 0.015 Transmission electron microscopy (TEM) images of O3 ceramics, where: (a)~(c) uncoated (Comparative Example 1), (d)~(f) coated for 0.5h (Example 1), (g)~(i) coated for 1h (Example 2), (j)~(l) coated for 2h (Example 3); image comparison revealed that as the coating time increased, the thickness of the outer coating layer of the ceramic sample gradually increased, and the coating became more obvious, which promoted the decrease of sintering temperature.

[0059] 4. Elemental Distribution Analysis Figure 4 The ZnO-B2O3-SiO2 glass-coated Sr prepared in Example 2 0.985 Lu 0.01 Ti 0.985 Ta 0.015 The EDS spectrum of O3 ceramics, through elemental distribution analysis, revealed the enrichment of ZnO-B2O3-SiO2 on the surface of the ceramic powder, indicating that the preparation method of this invention successfully coated the ceramic sample with a layer of zinc borosilicate glass.

[0060] 5. Analysis of Dielectric Properties as a Perturbation by Temperature Figure 5 Sr-coated ZnO-B2O3-SiO2 glass at different coating times 0.985 Lu 0.01 Ti 0.985 Ta 0.015 The graph shows the dielectric properties of O3 ceramics as a function of temperature, where: (a) dielectric constant, (b) dielectric loss, and (c) rate of change of dielectric constant. Figure 5In the text, T=0h represents the sample prepared in Comparative Example 1, T=0.5h represents the sample prepared in Example 1, T=1h represents the sample prepared in Example 2, and T=2h represents the sample prepared in Example 3. According to... Figure 5 It can be seen that the thermal stability of the ceramic sample is better and better as the coating time increases. The sample with a coating time of 1 h has both excellent dielectric properties at 1 kHz (dielectric constant of ~185663 and dielectric loss of ~0.0257) and thermal stability over a wide temperature range (25~300℃).

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a glass-coated strontium titanate-based giant dielectric ceramic material, characterized in that, Includes the following steps: Strontium titanate-based ceramic powder dispersion was mixed with zinc borosilicate glass sol for coating, resulting in zinc borosilicate glass sol-coated strontium titanate-based ceramic powder; the chemical formula of the strontium titanate-based ceramic powder is shown in Formula I: Sr 0.985 Lu 0.01 Ti 1-x The x O3 formula I; In Equation I: x is 0.005~0.02; The zinc borosilicate glass sol-coated strontium titanate ceramic powder, binder and water are mixed and then pressed, aged, crushed and shaped in sequence to obtain a ceramic green body; The ceramic preform is debinded and then sintered to obtain a glass-coated strontium titanate-based giant dielectric ceramic material; the sintering atmosphere is nitrogen.

2. The preparation method according to claim 1, characterized in that, The preparation method of the strontium titanate-based ceramic powder includes: mixing strontium carbonate, titanium dioxide, lutetium oxide and tantalum pentoxide to obtain raw material powder; pre-synthesizing the raw material powder by ball milling once, and then ball milling and sieving a second time to obtain the strontium titanate-based ceramic powder.

3. The preparation method according to claim 2, characterized in that, The pre-synthesis temperature is 1150~1250℃, the holding time is 3~5h, and the heating rate to the pre-synthesis temperature is 4~6℃ / min.

4. The preparation method according to claim 1, characterized in that, The preparation method of the zinc borosilicate glass sol includes: dissolving zinc nitrate and boric acid in water under acidic conditions to obtain zinc borosilicate sol; hydrolyzing silicate ester in ethanol to obtain silica sol; and mixing the silica sol and zinc borosilicate sol to react and obtain zinc borosilicate glass sol.

5. The preparation method according to claim 1 or 4, characterized in that, Based on the total molar amount of ZnO, B2O3 and SiO2 as 100%, the molar fraction of zinc nitrate is 35-55%, the molar fraction of boric acid is 10-25%, and the molar fraction of silicate ester is 35-50%.

6. The preparation method according to claim 1, characterized in that, The mass ratio of zinc borosilicate glass in the zinc borosilicate glass sol to strontium titanate-based ceramic powder in the strontium titanate-based ceramic powder dispersion is 0.5~1:1; the coating time is 0.5~2h.

7. The preparation method according to claim 1, characterized in that, In zinc borosilicate glass sol-coated strontium titanate-based ceramic powder, the thickness of the zinc borosilicate glass sol coating layer is 3~10 nm.

8. The preparation method according to claim 1, characterized in that, The binder is a polyvinyl alcohol solution, and the amount of the binder is 1-2% of the mass of the strontium titanate ceramic powder coated with the zinc borosilicate glass sol; the amount of water is 0.5-1% of the mass of the strontium titanate ceramic powder coated with the zinc borosilicate glass sol.

9. The preparation method according to claim 1, characterized in that, The temperature for removing the adhesive is 550~650℃, and the holding time is 1.5~2.5h; the temperature for sintering is 1400~1500℃, and the holding time is 3~5h.

10. The glass-coated strontium titanate-based giant dielectric ceramic material prepared by the preparation method according to any one of claims 1 to 9, characterized in that, It includes strontium titanate-based ceramic material and zinc borosilicate glass coated on the surface of the strontium titanate-based ceramic material.

Images