Foamed ceramic based on copper-molybdenum tailings and method for its preparation

Abstract

The application discloses a kind of based on copper-molybdenum tailings foamed ceramics and its preparation method, according to weight fraction, foamed ceramic raw materials include the following components: copper-molybdenum tailings 55~80 parts, potassium feldspar 5~20 parts, fluxing agent 25 parts, foaming agent 0.5~1.5 parts and stable foam agent 1~3 parts;Wherein: the fluxing agent is composed of sodium carbonate and waste glass, and the mass percentage of sodium carbonate in fluxing agent is 12~32%;The foaming agent is composed of dolomite and silicon carbide;The stable foam agent is calcium phosphate.By dry ball milling after mixing raw materials are evenly laid in the mold, finally sintered at 940~990 ℃ temperature is prepared.The foamed ceramics obtained by the application has small density, high compressive strength and low thermal conductivity, and the sintering temperature is reduced to 940~990 ℃ while achieving high content utilization of copper-molybdenum tailings, reducing energy consumption in the sintering process, and having good economic and social benefits.

Description

Technical Field

[0001] This invention belongs to the field of foamed ceramics technology for building applications, specifically relating to a foamed ceramic based on copper-molybdenum tailings and its preparation method. Background Technology

[0002] Copper-molybdenum tailings are industrial waste generated during the mining and beneficiation of copper and molybdenum ore. They generally contain a variety of heavy metal elements. Copper-molybdenum tailings have a high annual output, a large total stockpile, and a low comprehensive utilization rate, which easily causes pollution and damage to the environment and ecology.

[0003] Foamed ceramic materials are a new type of building material developed in recent years, possessing advantages such as light weight, high hardness, and low thermal conductivity. Copper-molybdenum tailings, after proper treatment, can be used as a high-quality raw material for firing foamed ceramics. Utilizing copper-molybdenum tailings to fire foamed ceramics is an effective method for transforming industrial waste into high-value-added products.

[0004] Chinese invention patent CN104926283 A (A building ceramic prepared using copper-molybdenum tailings and its preparation method) discloses a building ceramic prepared using copper-molybdenum tailings and its preparation method. It adopts wet ball milling and pressing molding processes, and the preparation process is relatively complex. The firing temperature of the ceramic floor tiles is 1160±10℃, and the firing temperature of the ceramic interior wall tile blank is 1080±10℃. The firing temperature of both ceramic materials is significantly higher than 1000℃.

[0005] Chinese invention patent CN103936454 A (A porous heat-insulating ceramic with gold and copper tailings as the main raw material and its preparation method) introduces a porous heat-insulating ceramic with gold and copper tailings as the main raw material and its preparation method. The sintering temperature is 1000-1100℃, the amount of silicon carbide in the foaming agent is large, the ball milling time is long, and molding is required. The resulting foamed ceramic has poor pore roundness and excessively large pore size.

[0006] Chinese invention patent CN107500800 B (Porous ceramic material containing copper tailings and its preparation method) discloses a porous ceramic material containing copper tailings and its preparation method, but the sintering temperature is between 1140 and 1180℃, which is relatively high, and repeated acid leaching treatment is required, making the preparation process quite complex.

[0007] Chinese invention patent CN105541296 A (A method for preparing ceramic materials using copper tailings) discloses a method for preparing ceramic materials using copper tailings, wherein the amount of copper tailings used is only 35 to 55 parts, the firing temperature is 1080 to 1160℃, which is relatively high, and wet ball milling and pressing or extrusion molding processes are also adopted.

[0008] In summary, existing technologies for preparing foamed ceramics using copper-containing tailings involve high sintering temperatures, mostly between 1000 and 1180°C, resulting in long firing cycles and significant energy consumption. Furthermore, the preparation process is complex, requiring numerous control parameters. Currently, wet ball milling is commonly used, which is time-consuming and energy-intensive. Combined with molding, spray drying, and other processes, this leads to long production cycles and high energy consumption. Summary of the Invention

[0009] To address the shortcomings of the existing technologies, this invention provides a foamed ceramic based on copper-molybdenum tailings and its preparation method. The foamed ceramic has uniform pore size and high sphericity, low density, high compressive strength, and low thermal conductivity. Furthermore, it incorporates a large amount of copper-molybdenum tailings, has a low sintering temperature during preparation, and a simple process, which is beneficial for industrial application.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] This invention provides a foamed ceramic based on copper-molybdenum tailings. By weight, the raw materials include the following components: 55-80 parts copper-molybdenum tailings, 5-20 parts potassium feldspar, 25 parts flux, 0.5-1.5 parts foaming agent, and 1-3 parts foam stabilizer; wherein:

[0012] The flux is composed of sodium carbonate and waste glass, with sodium carbonate accounting for 12-32% of the flux by mass; the foaming agent is composed of dolomite and silicon carbide; and the foam stabilizer is calcium phosphate.

[0013] According to the above scheme, the main chemical composition of the copper-molybdenum tailings by weight percentage is: SiO2 66-71wt%, Al2O3 15-20wt%, CaO 0.5-3.0wt%, MgO 0.5-3.0wt%, K2O 2-4wt%, Na2O 2-4wt%, Fe2O3 0.2-1.8wt%, CuO 0.06-0.15wt%, and MoO3 0.01-0.15wt%.

[0014] According to the above scheme, the mass percentage of sodium carbonate in the flux is 15-25%.

[0015] According to the above scheme, the mass ratio of dolomite to silicon carbide in the foaming agent is 4:1 to 5:1.

[0016] According to the above scheme, the density of the foamed ceramic based on copper-molybdenum tailings is 400-850 kg / m³. 3 The compressive strength is 4.77–19.25 MPa; the thermal conductivity is less than 0.15 W / (m·K).

[0017] According to the above scheme, the sintering temperature of the copper-molybdenum tailings-based foamed ceramic is 940–990℃.

[0018] According to the above scheme, the raw materials are mixed by dry ball milling and then evenly spread into the mold, and finally sintered at a temperature of 940-990℃ to obtain the product.

[0019] A method for preparing foamed ceramics based on copper-molybdenum tailings is provided, comprising the following steps:

[0020] 1) Ball milling and mixing: Dry ball milling and mixing of dried copper-molybdenum tailings, potassium feldspar, and waste glass; then mixing the ball-milled copper-molybdenum tailings, potassium feldspar, and waste glass with sodium carbonate, foaming agent, and foam stabilizer, followed by dry ball milling and mixing, passing through a 200-mesh sieve, and drying to obtain mixed powder.

[0021] 2) Evenly spread the material: spread the dried mixed powder obtained in step 1) evenly into the mold, vibrate it to compact it, and scrape the surface of the mixed material to make it smooth.

[0022] 3) Low-temperature firing: The mold containing the mixed powder obtained in step 2) is sintered at a temperature of 940 to 990°C, and then cooled to obtain copper-molybdenum tailings-based foamed ceramics.

[0023] According to the above scheme, in step 1), the drying conditions are: rapid drying at 130-150℃ for 1-3 hours.

[0024] According to the above scheme, in step 1), copper-molybdenum tailings, potassium feldspar, and waste glass are dry ball-milled for 0.5 to 1 hour; then the ball-milled copper-molybdenum tailings, potassium feldspar, and waste glass are mixed with sodium carbonate, foaming agent, and foam stabilizer and then dry ball-milled for 1 to 2 hours.

[0025] According to the above scheme, in step 1), the sieving is done through a 200-mesh sieve.

[0026] According to the above scheme, in step 3), the sintering time is 15-25 minutes.

[0027] According to the above scheme, in step 3), the sintering temperature is 950-980℃.

[0028] According to the above scheme, the heating program in step 3) is as follows: room temperature - 730℃, heating rate is 8~12℃ / min; 730℃ - 900℃, heating rate is 8~10℃ / min; hold at 900℃ for 5~10min; 900℃ - sintering temperature, heating rate is 3~4℃ / min.

[0029] This invention provides a low-temperature fired copper-molybdenum tailings foamed ceramic, using copper-molybdenum tailings and potassium feldspar as main raw materials, combined with sodium carbonate and waste glass as fluxes, dolomite and silicon carbide as foaming agents, and calcium phosphate as a foam stabilizer. The ceramic is obtained by further processing the following:

[0030] By mixing waste glass and sodium carbonate in a suitable ratio as a flux, the waste glass, with its low melting temperature (beginning vitrification at approximately 730°C), increases the liquid phase ratio and fluidity of the mixture at high temperatures, better encapsulating the gas generated by the foaming agent at high temperatures, which then forms pores upon cooling. Meanwhile, sodium carbonate generates a significant amount of free Na₂O upon melting at high temperatures. The Na₂O and K₂O in the mixture can disrupt the [SiO₄] tetrahedral network structure in the raw materials at high temperatures, effectively lowering the eutectic point of the mixed powder and thus reducing the sintering temperature of the foamed ceramic to below 1000°C. Simultaneously, this invention introduces calcium phosphate as a foam stabilizer. Calcium phosphate can fill the gaps between pores, serving as a component of the foamed ceramic skeleton. Furthermore, calcium helps form an calcium feldspar crystal phase upon cooling, preventing excessive foaming due to the strong fluxing effect of waste glass and sodium carbonate, thus stabilizing the foam and improving the compressive strength of the foamed ceramic. Meanwhile, phosphorus can participate in the formation of the glass network structure, and iron can enter the phosphate glass network structure during firing, thereby reducing the adverse coloring effect of impurities in iron in the mixed powder.

[0031] Furthermore, using dolomite and silicon carbide as a mixed foaming agent, SiC oxidizes at high temperatures to generate gas, which is then encapsulated in the melted powder. Upon cooling, this forms a closed-cell structure of foamed ceramic. Dolomite, primarily composed of calcium and magnesium carbonate, slowly decomposes at 730–910℃ to produce carbon dioxide gas, while simultaneously providing free CaO and MgO to the mixed powder, thus acting as a flux. However, using dolomite alone as a foaming agent would significantly increase the amount required, potentially leading to excessively high CaO content in the mixed powder. This would cause rapid deterioration of the pores in the foamed ceramic, making it difficult to form uniform pores. Additionally, since the sintering temperature range is 940–990℃, the gas generated by premature decomposition of dolomite is likely to escape in large quantities, resulting in poor foaming performance. Therefore, using dolomite and silicon carbide as a mixed foaming agent, both assisting in foaming, ensures sufficient gas production while also acting as a flux.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. This invention provides a low-temperature sintered copper-molybdenum tailings foamed ceramic, using copper-molybdenum tailings and potassium feldspar as the main raw materials, combined with sodium carbonate and waste glass as fluxes, dolomite and silicon carbide as foaming agents, and calcium phosphate as a foam stabilizer. Specifically, the use of waste glass and sodium carbonate as fluxes effectively reduces the sintering temperature of the mixed powder. Simultaneously, the waste glass, as a low-melting-point raw material, melts at high temperatures to form a liquid phase, better encapsulating the gas generated by the foaming agent at high temperatures. Furthermore, potassium feldspar is used to adjust the viscosity of the mixed powder at high temperatures, broadening the melting range of the mixed powder. Within this range, the foaming agent generates gas at high temperatures, which is then encapsulated by the molten liquid phase and forms pores upon cooling. Meanwhile, the foam stabilizer calcium phosphate in the composition prevents excessive foaming after the mixed powder melts, thus avoiding severe deterioration of the pore size of the foamed ceramic. Through the synergistic use of flux, foaming agent, and foam stabilizer, high utilization of copper-molybdenum tailings is achieved while reducing the sintering temperature to 940–990℃, thus lowering energy consumption during the firing process. This results in the production of copper-molybdenum tailings foamed ceramics with low density, high compressive strength, and low thermal conductivity, demonstrating significant economic and social benefits.

[0034] 2. This invention provides a method for preparing low-temperature fired copper-molybdenum tailings foamed ceramics. The method employs a dry ball milling process, in which the resulting mixed powder is directly and uniformly spread in a mold for firing, eliminating the pressing and molding step. This not only optimizes the production process of foamed ceramics but also improves production efficiency, providing a simpler and more effective way for the large-scale manufacturing of foamed ceramics. Attached Figure Description

[0035] Figure 1 This is a stereomicroscopic image (1.5x magnification) of the copper-molybdenum tailings foamed ceramic in Embodiment 6 of the present invention. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The chemical composition of the copper-molybdenum tailings used in the examples was determined by X-ray fluorescence spectrometry. By weight percentage, it included 68.61 wt% SiO2, 17.42 wt% Al2O3, 0.96 wt% CaO, 0.94 wt% MgO, 1.30 wt% Fe2O3, 1.07 wt% SO3, 3.36 wt% K2O, 3.63 wt% Na2O, 0.13 wt% CuO, 0.01 wt% MoO3, with a loss on ignition of 1.81 wt%. It also contained trace amounts of rare earth elements.

[0038] In the examples and comparative examples, the flux was composed of sodium carbonate and waste glass; the foaming agent was composed of dolomite and silicon carbide, wherein the mass ratio of dolomite to silicon carbide was 4:1; and the foam stabilizer was calcium phosphate.

[0039] The standard ranges of density, compressive strength, and thermal conductivity in the performance indicators of foamed ceramic partition materials (T / CBCSA12-2019) are used as the screening criteria for qualified products, as shown in Table 1.

[0040] Table 1 Performance Indicators of Foamed Ceramic Partition Wall Materials (T / CBCSA12-2019)

[0041]

[0042]

[0043] Example 1

[0044] A method for preparing foamed ceramics from low-temperature sintered copper-molybdenum tailings is provided, comprising the following steps:

[0045] The dried copper-molybdenum tailings, potassium feldspar, and waste glass were each dry-ball milled for 0.5 hours. By weight, 70 parts of copper-molybdenum tailings, 5 parts of potassium feldspar, 25 parts of flux (including 21 parts of waste glass and 4 parts of sodium carbonate), 1 part of foaming agent (the mass ratio of dolomite to silicon carbide was 4:1), and 2 parts of foam stabilizer were weighed out. All materials were shaken and mixed, and then dry-ball milled for 1.5 hours. The mixture was passed through a 200-mesh sieve, and the undersize portion was rapidly dried at 150°C for 2 hours. The dried mixed powder was then evenly spread into a mold, compacted, and the surface of the mixed powder was leveled. The mold containing the mixed powder was fired using the following heating program: room temperature to 730℃, heating rate of 10℃ / min; 730℃ to 900℃, heating rate of 8℃ / min; holding at 900℃ for 5 min; 900℃ to 960℃, heating rate of 4℃ / min; holding at 960℃ for 20 min. After cooling in the furnace, it was processed and cut to obtain copper-molybdenum tailings foamed ceramics. The raw material composition and properties of this embodiment are shown in Table 2.

[0046] Example 2

[0047] The preparation steps are the same as in Example 1. Detailed raw material composition and properties are shown in Table 2.

[0048] Comparative Example 1

[0049] The preparation steps are the same as in Example 1. Detailed raw material composition and properties are shown in Table 2.

[0050] Table 2. Raw material composition and properties of Examples 1-2 and Comparative Example 1

[0051]

[0052] Table 2 shows that when the amount of sodium carbonate added is too small, as in Comparative Example 1, the density of the resulting copper-molybdenum tailings foamed ceramic is too high, exceeding 1 g / cm³. 3 This is because the amount of sodium carbonate added was too small, resulting in insufficient melting and foaming of the mixed powder. As the amount of sodium carbonate added increases, the density of the resulting ceramic gradually decreases. However, when the amount of sodium carbonate added is too high, it leads to excessive melting and foaming of the mixed powder, forming large pores with a diameter of over 3 mm. These pores have thin walls, resulting in weak support between the pore walls and thus reducing compressive strength. Even with the presence of a foam stabilizer, its effect is still limited. Therefore, a suitable ratio of waste glass and sodium carbonate in the flux can lower the sintering temperature while maintaining a balance between density, compressive strength, and thermal conductivity.

[0053] Example 3

[0054] A method for preparing foamed ceramics from low-temperature sintered copper-molybdenum tailings is provided, comprising the following steps:

[0055] The dried copper-molybdenum tailings, potassium feldspar, and waste glass were dry ball-milled for 0.5 hours respectively. By weight, 70 parts of copper-molybdenum tailings, 5 parts of potassium feldspar, 25 parts of flux (including 20 parts of waste glass and 5 parts of sodium carbonate), 1.0 part of foaming agent (the mass ratio of dolomite to silicon carbide is 4:1), and 1.0 part of foam stabilizer were weighed out. All materials were shaken and mixed, and then dry ball-milled for 1 hour. The mixture was passed through a 200-mesh sieve. The portion passing through the sieve was placed under 150℃ and dried rapidly for 2 hours. The dried mixed powder was then evenly spread into a mold, compacted, and the surface of the mixed powder was leveled. The mold containing the mixed powder is sintered according to the heating program, which is as follows: room temperature - 730℃, heating rate of 10℃ / min; 730℃ - 900℃, heating rate of 9℃ / min; holding at 900℃ for 10min; 900℃ - 960℃, heating rate of 4℃ / min; holding at 960℃ for 20min. After cooling in the furnace, it is processed and cut to obtain copper-molybdenum tailings foamed ceramics.

[0056] Examples 4-5

[0057] The preparation steps are the same as in Example 3, except that the foaming agent in the raw material composition of Examples 4 and 5 is 1.0 part and 1.5 parts, respectively. The raw material composition and performance are shown in Table 3.

[0058] Table 3. Raw material composition and properties in Examples 3-5

[0059]

[0060] Table 3 shows that as the amount of foaming agent added in Examples 3, 4, and 5 gradually increased, the apparent density, compressive strength, and thermal conductivity of the prepared foamed ceramic samples decreased accordingly. This is because when the amount of foaming agent increases, more gas is generated during the foaming process, the pores grow larger, resulting in larger pore sizes in the foamed ceramics and greater sample volume expansion, thus reducing the sample density. At the same time, due to the growth and aggregation of bubbles, the average pore size increases while the pore walls become thinner, weakening the supporting effect between the pore walls, leading to lower compressive strength and higher thermal conductivity of the samples.

[0061] Example 6

[0062] A method for preparing foamed ceramics from low-temperature sintered copper-molybdenum tailings is provided, comprising the following steps:

[0063] The dried copper-molybdenum tailings, potassium feldspar, and waste glass were dry-ball milled for 1 hour each. By weight, 55 parts of copper-molybdenum tailings, 20 parts of potassium feldspar, 25 parts of flux (including 20 parts waste glass and 5 parts sodium carbonate), 1.0 part of foaming agent (dolomite and silicon carbide in a 4:1 mass ratio), and 1.5 parts of foam stabilizer were weighed out. All materials were shaken and mixed thoroughly, then dry-ball milled for 1.5 hours. After milling, the mixture was passed through a 200-mesh sieve. The undersize portion was then rapidly dried at 150℃ for 2 hours to obtain a dry mixed powder. The dried mixed powder was evenly spread into a mold, compacted, and the surface was smoothed.

[0064] The mold containing the mixed powder is fired according to the heating program, which is as follows: room temperature - 730℃, heating rate is 10℃ / min; 730℃ - 900℃, heating rate is 9℃ / min; hold at 900℃ for 10min; 900℃ - 960℃, heating rate is 4℃ / min; hold at sintering temperature of 960℃ for 20min, cool in the furnace and then process and cut to obtain copper-molybdenum tailings foamed ceramic.

[0065] Figure 1 This is a stereomicroscopic image of the copper-molybdenum tailings foamed ceramic prepared in this embodiment. The image shows that the foamed ceramic has high pore circularity, uniform pore size, and moderate pore wall thickness.

[0066] Examples 7-8

[0067] The preparation steps of Examples 7 and 8 are the same as those of Example 6, and the detailed raw material composition and properties are shown in Table 4.

[0068] Table 4. Raw material composition and properties in Examples 6-8

[0069]

[0070] Table 4 shows that Examples 6, 7, and 8 all meet the performance indicators for densities of 500, 600, and 800, respectively, indicating that the prepared foamed ceramics have good performance.

[0071] Example 9

[0072] A method for preparing foamed ceramics from low-temperature sintered copper-molybdenum tailings is provided, comprising the following steps:

[0073] Dry ball milling was performed on the dried copper-molybdenum tailings, potassium feldspar, and waste glass for 1 hour each. By weight, 70 parts copper-molybdenum tailings, 5 parts potassium feldspar, flux (including 20 parts waste glass and 5 parts sodium carbonate), 1.0 part foaming agent (dolomite and sodium carbonate in a mass ratio of 4:1), and 1.5 parts foam stabilizer were weighed and mixed thoroughly before dry ball milling for 2 hours. After ball milling, the mixture was passed through a 200-mesh sieve. The undersize portion was then rapidly dried at 150℃ for 2 hours. The dried powder was then evenly spread into a mold, compacted, and the surface of the powder was leveled. The mold containing the mixed powder was sintered according to the heating program, which was as follows: room temperature - 730℃, 10℃ / min; 730℃ - 900℃, 8℃ / min; held at 900℃ for 8 min; 900℃ - 940℃, 4℃ / min; held at the sintering temperature for 20 min. After cooling, it was processed and cut to obtain copper-molybdenum tailings foamed ceramics. The properties of the foamed ceramics are shown in Table 5.

[0074] Examples 10-11

[0075] The preparation steps are the same as in Example 9, except that the sintering temperatures of Examples 10 and 11 are adjusted to 970℃ and 990℃, respectively. The performance is shown in Table 5.

[0076] Table 5. Performance of Examples 9-11

[0077] Example 9 940 849.3 19.25 0.099 Example 10 970 606.3 10.85 0.077 Example 11 990 518.2 7.06 0.069

[0078] Table 5 shows that in the firing conditions of Examples 9, 10 and 11, the sintering temperature gradually increases, while the density, compressive strength and thermal conductivity gradually decrease. Examples 9, 10 and 11 meet the standards with density designations of 800, 600 and 500, respectively.

[0079] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A foamed ceramic based on copper-molybdenum tailings, characterized in that, By weight, the raw materials include the following components: 55-80 parts copper-molybdenum tailings, 5-20 parts potassium feldspar, 25 parts flux, 0.5-1.5 parts foaming agent, and 1-3 parts foam stabilizer; wherein: The flux is composed of sodium carbonate and waste glass, with sodium carbonate accounting for 15-25% by mass in the flux; the foaming agent is composed of dolomite and silicon carbide; and the foam stabilizer is calcium phosphate. In the foaming agent, the mass ratio of dolomite to silicon carbide is 4:1 to 5:

1.

2. The foamed ceramic according to claim 1, characterized in that, The main chemical components of the copper-molybdenum tailings, by weight percentage, are: SiO2 66~71 wt%, Al2O3 15~20 wt%, CaO 0.5~3.0 wt%, MgO 0.5~3.0 wt%, K2O 2~4 wt%, Na2O 2~4 wt%, Fe2O3 0.2~1.8 wt%, CuO 0.06~0.15 wt%, and MoO3 0.01~0.15 wt%.

3. The foamed ceramic according to claim 1, characterized in that, The density of the foamed ceramic based on copper-molybdenum tailings is 400~850 kg / m³. 3 The compressive strength is 4.77~19.25 MPa. The thermal conductivity is less than 0.15 W / (m·K).

4. A method for preparing foamed ceramics based on copper-molybdenum tailings as described in any one of claims 1-3, characterized in that, Includes the following steps: 1) Ball milling and mixing: Dry ball milling and mixing of dried copper-molybdenum tailings, potassium feldspar, and waste glass; then mixing the ball-milled copper-molybdenum tailings, potassium feldspar, and waste glass with sodium carbonate, foaming agent, and foam stabilizer, followed by dry ball milling, sieving, and drying to obtain mixed powder. 2) Evenly spread the material: spread the dried mixed powder obtained in step 1) evenly into the mold, vibrate it to compact it, and scrape the surface of the mixed material to make it smooth. 3) Low-temperature firing: The mold containing the mixed powder obtained in step 2) is sintered at 940~990 ℃, and then cooled to obtain copper-molybdenum tailings-based foamed ceramics.

5. The preparation method according to claim 4, characterized in that, In step 1), copper-molybdenum tailings, potassium feldspar, and waste glass are dry ball-milled for 0.5 to 1 hour; then the ball-milled copper-molybdenum tailings, potassium feldspar, and waste glass are mixed with sodium carbonate, foaming agent, and foam stabilizer, and then dry ball-milled for 1 to 2 hours, passed through a 200-mesh sieve, and dried to obtain mixed powder.

6. The preparation method according to claim 4, characterized in that, In step 1), the drying conditions are: drying at 130~150℃ for 1~3 h.

7. The preparation method according to claim 4, characterized in that, In step 3), the sintering time is 15~25min.

8. The preparation method according to claim 4, characterized in that, The heating program in step 3) is as follows: room temperature - 730℃, heating rate is 8~12℃ / min; 730℃ - 900℃, heating rate is 8~10℃ / min; hold at 900℃ for 5~10min; 900℃ to sintering temperature, heating rate is 3~4℃ / min.

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