A method for preparing a high-optical-quality SrZrO3 perovskite dielectric ceramic

Abstract

The application relates to a preparation method of a high-optical-quality SrZrO3 perovskite dielectric ceramic. Strontium chloride hexahydrate is added into deionized water to prepare a salt solution with a certain concentration. The uniformly dissolved salt solution is added drop by drop into an (NH4)2CO3 solution to react to generate a precipitate, and after aging, the precipitate is sequentially subjected to washing and drying to obtain strontium carbonate powder. The strontium carbonate powder and 20-nanometer ZrO2 powder on the market are added into a ball mill tank according to a molar ratio of 1:1, and ball milling is carried out in anhydrous ethanol as a medium. After ball milling, the calcination product is obtained by calcining in a muffle furnace; then, the calcination product is subjected to cold isostatic pressing forming, vacuum sintering and polishing treatment, and finally, the SrZrO3 transparent ceramic material with excellent optical properties is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing a SrZrO3 perovskite dielectric ceramic with high optical quality. BACKGROUND

[0002] Dielectric ceramics, also known as dielectric ceramics, are a kind of ceramic materials with polarization ability and can establish an electric field in the body for a long time. Dielectric ceramics have excellent dielectric properties, mechanical strength, chemical stability and thermal stability, and are widely used in the electronic field. Among them, capacitors are one of the important application fields of dielectric ceramics. The high dielectric constant and low dielectric loss of dielectric ceramics make the capacitor have higher capacitance value and lower energy loss. With the continuous development of science and technology, the requirements for capacitors are more stringent, and dielectric materials with high transmittance have wide application prospects in display technology and energy.

[0003] ABO3 type transparent ceramic is a kind of polycrystalline material with perovskite crystal structure, which has high transparency, high strength, high hardness, good electrical insulation and corrosion resistance, etc. It is widely used in new lighting technology, observation window in high temperature and high pressure and corrosion environment, window for infrared detection, protective fairing for missiles, transparent armor for military, capacitor, dielectric resonator, integrated circuit substrate, filter, etc. SrZrO3 belongs to ABO3 type material, if the transparency of SrZrO3 can be realized, it will become a new type of transparent dielectric ceramic material.

[0004] CN110818409B discloses a method for preparing SrZrO3 and SrZrO3 ceramic, which mixes SrCO3 and ZrO2, presses into a blank, and then places it in a microwave environment for processing, including powder processing or bulk processing. The powder processing is heated to 1100-1400℃, and the temperature is kept for not less than 30min to obtain SrZrO3 powder; the bulk processing is to add powder and sinter, heat to 1200-1650℃ at a rate of 5-25℃ / min, and keep the temperature for not less than 30min to obtain SrZrO3 bulk. The method does not realize the transparency of SrZrO3 ceramic.

[0005] Shi Feng (J. Mater. Res., 2016, 31

[20] , 3249-3254) et al. used commercially available SrCO3 and ZrO2 as raw materials, synthesized SrZrO3 powder by solid phase reaction method, and then prepared SrZrO3 ceramic through dry pressing at 82MPa and high temperature sintering at 1500℃. The method also does not realize the transparency of SrZrO3 ceramic.

[0006] The biggest factor contributing to the opacity of ceramic materials is the scattering of light by pores within the material. The presence of pores seriously impairs the performance of ceramic materials. Therefore, a practical method is needed to prepare SrZrO3 perovskite-type transparent ceramics.

[0007] Pressureless sintering (vacuum sintering, atmosphere sintering) has the advantages of low cost, time saving and high efficiency compared with pressure-assisted sintering (hot pressing sintering, hot isostatic pressing sintering), but pressureless sintering requires the initial powder to have high sintering activity.

[0008] The technical problem solved by this invention is to provide a method for preparing high-optical-quality SrZrO3 perovskite dielectric ceramics to achieve high densification of SrZrO3 ceramics. SrCO3 powder is prepared using strontium chloride hexahydrate as a raw material and (NH4)2CO3 as a precipitant. Using the self-prepared SrCO3 powder and commercially available ZrO2 powder as raw materials, highly sinterable SrZrO3 powder is synthesized through ball milling and high-temperature solid-state reaction. The green body formed by cold isostatic pressing is then subjected to high-temperature vacuum sintering to obtain a high-density transparent SrZrO3 ceramic material. Summary of the Invention

[0009] The technical solution of this invention is:

[0010] A method for preparing high-optical-quality SrZrO3 perovskite dielectric ceramics, the specific steps of which are as follows:

[0011] (1) Dissolve strontium chloride hexahydrate in deionized water to prepare a clear mother salt solution;

[0012] (2) The mother salt solution prepared in step (1) is titrated into (NH4)2CO3 solution at a certain dropping rate to react and generate a white precipitate. Then, it is aged, washed and dried to obtain SrCO3 powder.

[0013] (3) The SrCO3 powder obtained in step (2) and commercially available 20 nm ZrO2 powder were added to a ball mill jar at a cation molar ratio of 1:1, and ball milled with anhydrous ethanol as the medium. The precursor was then dried.

[0014] (4) The precursor obtained in step (3) is calcined in a muffle furnace to obtain the calcined product;

[0015] (5) The calcined product obtained in step (4) is cold isostatically pressed and sintered at high temperature under vacuum to obtain dense SrZrO3 ceramic; finally, the sample is ground and polished to obtain transparent SrZrO3 ceramic.

[0016] Furthermore, in step (1), the cation concentration in the mother salt solution is 0.24 mol / L to 0.48 mol / L.

[0017] Furthermore, in step (2), the molar ratio of the mother salt solution to the precipitant is 1:1 to 1:3.

[0018] Furthermore, in step (2), the precipitant (NH4)2CO3 solution is prepared by dissolving solid (NH4)2CO3 in deionized water, and the concentration of the (NH4)2CO3 solution is 0.9mol / L~2.0mol / L.

[0019] Furthermore, in step (2), the titration rate of the salt solution is 1 mL / min to 5 mL / min, and the aging time is 30 min to 2 h.

[0020] Furthermore, in step (2), the number of times of washing with deionized water is 2 to 6, and the number of times of washing with anhydrous ethanol is 1 to 5; the drying temperature of the oven is 80℃ to 150℃, and the drying time is 12h to 24h.

[0021] Furthermore, in step (3), the ball milling time is 8h~24h, the drying temperature is 80℃~150℃, and the drying time is 12h~24h.

[0022] Furthermore, in step (4), the calcination temperature of the muffle furnace is 500℃~1300℃, and the holding time is 2h~5h.

[0023] Furthermore, in step (5), the pressure during cold isostatic pressing is 100MPa~300MPa.

[0024] Furthermore, in step (5), the sintering temperature is controlled at 1700℃~1800℃ and the holding time is 3h~8h.

[0025] Compared with the prior art, the advantages of the present invention are as follows:

[0026] Currently, there are no reports of achieving high transparency in SrZrO3 ceramics, either domestically or internationally. This invention uses SrCO3 synthesized by chemical precipitation and commercially available 20nm ZrO2 powder as raw materials, and successfully prepares perovskite-type transparent ceramics with high optical quality through ball milling, solid-state reaction, cold isostatic pressing, and vacuum sintering. Ball milling effectively controls the mixing degree and particle size of the powders. Sintering the ceramics under high temperature and vacuum promotes the elimination of pores within the ceramic body, which is beneficial for obtaining high-density ceramic materials. Using the method of this invention, SrZrO3 optical functional ceramic materials with high transmittance have broad application prospects in electronics, communications, aerospace, and other fields. This invention marks the first time internationally that high transparency has been achieved in SrZrO3 ceramics. Attached image description:

[0028] Figure 1The X-ray diffraction pattern of the ceramic powder obtained by the preparation method of the present invention (corresponding to Example 3);

[0029] Figure 2 The X-ray diffraction pattern of the transparent ceramic obtained by the preparation method of the present invention (corresponding to Example 2);

[0030] Figure 3 These are photographs of the appearance of SrZrO3 ceramics obtained by the preparation method of the present invention (corresponding to Example 1);

[0031] Figure 4 These are photographs of the appearance of SrZrO3 ceramics obtained by the preparation method of the present invention (corresponding to Example 2);

[0032] Figure 5 These are photographs of the appearance of SrZrO3 ceramics obtained by the preparation method of the present invention (corresponding to Example 3);

[0033] Figure 6 These are photographs of the appearance of SrZrO3 ceramics obtained by the preparation method of the present invention (corresponding to Example 4);

[0034] Figure 7 The transmittance curve of SrZrO3 ceramic obtained by the preparation method of the present invention (corresponding to Example 1) is shown.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0036] Example 1

[0037] Step 1: Dissolve strontium chloride hexahydrate in deionized water to prepare a mother salt solution with a concentration of 0.42 mol / L, and stir until the solution is clear;

[0038] Step 2: The salt solution obtained in Step 1 is titrated into a 1.8 mol / L (NH4)2CO3 solution at a dropping rate of 2.5 mL / min to form a white precipitate. The molar ratio of the mother salt solution to the precipitant is 1:1.7. The solution is then aged for 30 min, washed three times with deionized water, washed once with anhydrous ethanol, and kept at 150℃ for 12 h to obtain dry SrCO3 powder.

[0039] Step 3: Add the powder obtained in Step 2 and commercially available 20 nm zirconium dioxide powder to a ball mill jar at a cation ratio of 1:1, and ball mill for 8 h with anhydrous ethanol as the medium. Then keep it at 150 °C for 12 h to obtain a dry mixed powder.

[0040] Step 4: Calcine the mixed powder obtained in Step 3 in a muffle furnace at 500℃ for 2 hours to obtain the calcined product;

[0041] Step 5: The calcined product obtained in Step 4 is cold isostatically pressed at a pressure of 240 MPa, and then sintered at 1800℃ for 5 h under vacuum to obtain SrZrO3 ceramic. Finally, the sample is ground and polished to obtain SrZrO3 transparent ceramic.

[0042] Example 2

[0043] Step 1: Dissolve strontium chloride hexahydrate in deionized water to prepare a mother salt solution with a concentration of 0.36 mol / L, and stir until the solution is clear;

[0044] Step 2: The salt solution obtained in Step 1 is titrated into a 1.5 mol / L (NH4)2CO3 solution at a dropping rate of 1 mL / min to form a white precipitate. The molar ratio of the mother salt solution to the precipitant is 1:1.7. After aging for 1 h, the solution is washed twice with deionized water and three times with anhydrous ethanol. The solution is then kept at 140℃ for 24 h to obtain dry SrCO3 powder.

[0045] Step 3: Add the powder obtained in Step 2 and commercially available 20 nm zirconium dioxide powder to a ball mill jar at a cation ratio of 1:1, and ball mill for 10 h with anhydrous ethanol as the medium. Then keep it at 140 °C for 18 h to obtain a dry mixed powder.

[0046] Step 4: Calcine the mixed powder obtained in Step 3 in a muffle furnace at 500℃ for 4 hours to obtain the calcined product;

[0047] Step 5: The calcined product obtained in Step 4 is cold isostatically pressed at a pressure of 240 MPa, and then sintered at 1800℃ for 5 h under vacuum to obtain SrZrO3 ceramic. Finally, the sample is ground and polished to obtain SrZrO3 transparent ceramic.

[0048] Example 3

[0049] Step 1: Dissolve strontium chloride hexahydrate in deionized water to prepare a mother salt solution with a concentration of 0.48 mol / L, and stir until the solution is clear;

[0050] Step 2: The salt solution obtained in Step 1 is titrated into a 0.9 mol / L (NH4)2CO3 solution at a dropping rate of 1 mL / min to form a white precipitate. The molar ratio of the mother salt solution to the precipitant is 1:1.5. After aging for 2 h, the solution is washed 6 times with deionized water and 5 times with anhydrous ethanol. The solution is then kept at 150℃ for 18 h to obtain dry SrCO3 powder.

[0051] Step 3: Add the powder obtained in Step 2 and commercially available 20 nm zirconium dioxide powder to a ball mill jar at a cation ratio of 1:1, and ball mill for 12 h with anhydrous ethanol as the medium. Then keep it at 150 °C for 12 h to obtain a dry mixed powder.

[0052] Step 4: Calcine the mixed powder obtained in Step 3 in a muffle furnace at 900℃ for 2 hours to obtain the calcined product;

[0053] Step 5: The calcined product obtained in Step 4 is cold isostatically pressed at a pressure of 300 MPa, and then sintered at 1800℃ for 5 h under vacuum to obtain SrZrO3 ceramic. Finally, the sample is ground and polished to obtain SrZrO3 transparent ceramic.

[0054] Example 4

[0055] Step 1: Dissolve strontium chloride hexahydrate in deionized water to prepare a mother salt solution with a concentration of 0.36 mol / L, and stir until the solution is clear;

[0056] Step 2: The salt solution obtained in Step 1 is titrated into a 1.5 mol / L (NH4)2CO3 solution at a dropping rate of 5 mL / min to form a white precipitate. The molar ratio of the mother salt solution to the precipitant is 1:1.5. After aging for 1 h, the solution is washed three times with deionized water and twice with anhydrous ethanol. The solution is then kept at 150 °C for 14 h to obtain dry SrCO3 powder.

[0057] Step 3: Add the powder obtained in Step 2 and commercially available 20 nm zirconium dioxide powder to a ball mill jar at a cation ratio of 1:1, and ball mill for 8 h with anhydrous ethanol as the medium. Then keep it at 150 °C for 14 h to obtain a dry mixed powder.

[0058] Step 4: Calcine the mixed powder obtained in Step 3 in a muffle furnace at 1300℃ for 2 hours to obtain the calcined product;

[0059] Step 5: The calcined product obtained in Step 4 is cold isostatically pressed at a pressure of 240 MPa, and then sintered at 1800℃ for 5 h under vacuum to obtain SrZrO3 ceramic. Finally, the sample is ground and polished to obtain SrZrO3 transparent ceramic.

[0060] Example 5

[0061] Step 1: Dissolve strontium chloride hexahydrate in deionized water to prepare a mother salt solution with a concentration of 0.24 mol / L, and stir until the solution is clear;

[0062] Step 2: The salt solution obtained in Step 1 is titrated into a 2 mol / L (NH4)2CO3 solution at a dropping rate of 3 mL / min to form a white precipitate. The molar ratio of the mother salt solution to the precipitant is 1:1. After aging for 2 h, the solution is washed three times with deionized water and once with anhydrous ethanol. The solution is then kept at 80 °C for 24 h to obtain dry SrCO3 powder.

[0063] Step 3: Add the powder obtained in Step 2 and commercially available 20 nm zirconium dioxide powder to a ball mill jar at a cation ratio of 1:1, and ball mill for 12 h with anhydrous ethanol as the medium. Then keep it at 140 °C for 24 h to obtain a dry mixed powder.

[0064] Step 4: Calcine the mixed powder obtained in Step 3 in a muffle furnace at 1100℃ for 5 hours to obtain the calcined product;

[0065] Step 5: The calcined product obtained in Step 4 is cold isostatically pressed at a pressure of 100 MPa, and then sintered at 1700℃ for 8 hours under vacuum to obtain SrZrO3 ceramic. Finally, the sample is ground and polished to obtain SrZrO3 transparent ceramic.

[0066] Example 6

[0067] Step 1: Dissolve strontium chloride hexahydrate in deionized water to prepare a mother salt solution with a concentration of 0.24 mol / L, and stir until the solution is clear;

[0068] Step 2: The salt solution obtained in Step 1 is titrated into a 0.9 mol / L (NH4)2CO3 solution at a dropping rate of 5 mL / min to form a white precipitate. The molar ratio of the mother salt solution to the precipitant is 1:3. After aging for 1 h, the solution is washed 4 times with deionized water and 2 times with anhydrous ethanol. The solution is then kept at 100℃ for 18 h to obtain dry SrCO3 powder.

[0069] Step 3: Add the powder obtained in Step 2 and commercially available 20 nm zirconium dioxide powder to a ball mill jar at a cation ratio of 1:1, and ball mill for 24 h with anhydrous ethanol as the medium. Then keep it at 80 °C for 12 h to obtain a dry mixed powder.

[0070] Step 4: Calcine the mixed powder obtained in Step 3 in a muffle furnace at 1300℃ for 2 hours to obtain the calcined product;

[0071] Step 5: The calcined product obtained in Step 4 is cold isostatically pressed at a pressure of 200 MPa, and then sintered at 1800℃ for 3 hours under vacuum to obtain SrZrO3 ceramic. Finally, the sample is ground and polished to obtain SrZrO3 transparent ceramic.

[0072] Figure 1 The X-ray diffraction (XRD) pattern of the SrZrO3 ceramic powder prepared in Example 3 is given. Figure 2 The horizontal axis 2θ represents the scanning angle, and the vertical axis Intensity represents the intensity. From Figure 2 It can be seen that the powder exhibits the structural characteristics of SrZrO3, which is a perovskite structure, with sharp diffraction peaks and good crystallinity.

[0073] Figure 2 X-ray diffraction (XRD) patterns of the transparent SrZrO3 ceramic prepared by the method in Example 2 are presented. The ceramic also exhibits the structural characteristics of SrZrO3. Compared with the powder sample, the ceramic has higher diffraction peak intensities and sharper peaks, indicating better crystallinity.

[0074] Figure 3 , Figure 4 , Figure 5 , Figure 6 Photographs of polished samples obtained after grinding and polishing of SrZrO3 ceramics prepared according to the methods of Examples 1, 2, 3, and 4 are shown respectively. Figure 3 , Figure 4 , Figure 5 , Figure 6 As can be seen, the polished ceramics have high optical quality, and text can be read through the ceramic samples. Compared to the four sample images, there are differences in the optical quality and sample size of the ceramic samples. The ceramic sample obtained in Example 1 has a small volume and the highest optical quality, indicating that the ceramic body had a high shrinkage rate during sintering, making the ceramic more dense and thus improving its optical quality. The process parameters of the preparation process directly affect the sintering activity of the initial powder, and different sintering processes will also affect the transmittance of the ceramic to varying degrees.

[0075] Figure 7 The transmittance curves of SrZrO3 ceramics prepared by the preparation method of Example 1 are given. Figure 7 The horizontal axis represents wavelength, and the vertical axis represents transmittance. Testing showed that the SrZrO3 transparent ceramic prepared in this invention has a transmittance of approximately 75% at a wavelength of 521 nm.

[0076] The above are merely specific embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-optical-quality SrZrO3 perovskite dielectric ceramic, the specific steps of which are: (1) Dissolve strontium chloride hexahydrate in deionized water to prepare a clear mother salt solution; (2) Using (NH4)2CO3 solution as a precipitant, the mother salt solution prepared in step (1) is titrated into ammonium carbonate solution at a certain dropping rate to react and generate a white precipitate. Then, it is aged, washed and dried to obtain SrCO3 powder. (3) The powder obtained in step (2) and commercially available 20 nm ZrO2 powder are added to a ball mill jar at a cationic molar ratio of 1:1, ball milled with anhydrous ethanol as the medium, and dried to obtain a dry mixed powder. (4) Calcine the mixture obtained in step (3) in a muffle furnace at a temperature of 500℃~1300℃ for 2h~5h. (5) The calcined product obtained in step (4) is subjected to cold isostatic pressing; (6) The blank obtained in step (5) is sintered at high temperature under vacuum. The sintering temperature is 1700℃~1800℃ and the holding time is 3h~8h. Finally, the sintered body is ground and polished to obtain SrZrO3 transparent ceramic.

2. The method for preparing a high-optical-quality SrZrO3 perovskite dielectric ceramic according to claim 1, characterized in that: In step (1), the cation concentration in the mother salt solution is 0.24 mol / L to 0.48 mol / L.

3. The method for preparing a high-optical-quality SrZrO3 perovskite dielectric ceramic according to claim 1, characterized in that: In step (2), the molar ratio of the mother salt solution to the precipitant is 1:1 to 1:

3.

4. The method for preparing a high-optical-quality SrZrO3 perovskite dielectric ceramic according to claim 1, characterized in that: In step (2), the precipitant (NH4)2CO3 solution is prepared by dissolving solid (NH4)2CO3 in deionized water, and the concentration of the (NH4)2CO3 solution is 0.9 mol / L to 2.0 mol / L.

5. The method for preparing a high-optical-quality SrZrO3 perovskite dielectric ceramic according to claim 1, characterized in that: In step (2), the titration rate of the mother salt solution is 1 mL / min to 5 mL / min, and the aging time is 30 min to 2 h.

6. The method for preparing a high-optical-quality SrZrO3 perovskite dielectric ceramic according to claim 1, characterized in that: In step (2), the number of times of washing with deionized water is 2 to 6, and the number of times of washing with anhydrous ethanol is 1 to 5; the drying temperature of the oven is 80℃ to 150℃, and the drying time is 12h to 24h.

7. The method for preparing a high-optical-quality SrZrO3 perovskite dielectric ceramic according to claim 1, characterized in that: In step (3), the ball milling time is 8h~24h, the drying temperature is 80℃~150℃, and the drying time is 12h~24h.

8. The method for preparing a high-optical-quality SrZrO3 perovskite dielectric ceramic according to claim 1, characterized in that: In step (5), the cold isostatic pressing pressure is 100MPa~300MPa.

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