Method for preparing calcium-doped barium titanate ultrafine powder under alkaline condition

Abstract

The invention belongs to the field of ceramic materials of electronic components, and particularly relates to a method for preparing calcium-doped barium titanate ultrafine powder under an alkaline condition, which comprises the following steps: (1) weighing barium carbonate powder, titanium dioxide powder and calcium carbonate powder as raw material powder according to a chemical formula (Ba0. 98Ca0. 02) xTiO3, adding water, a dispersing agent and ammonia water, mixing, carrying out first sanding, and carrying out second sanding to obtain a mixed powder; first slurry is obtained; (2) drying, sieving and low-temperature calcining the obtained first slurry to obtain first powder; (3) performing secondary sanding on the obtained first powder, water, a dispersing agent and ammonia water to obtain second slurry; (4) performing drying, sieving and high-temperature calcination on the obtained second slurry to obtain second powder; (5) sieving the obtained second powder, adding an organic solvent, and carrying out third sanding to obtain third slurry; and (6) drying and sieving the obtained third slurry to obtain the calcium-doped barium titanate ultrafine powder.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ceramic materials for electronic components, and particularly relates to a method for preparing calcium-doped barium titanate ultrafine powder under alkaline conditions. BACKGROUND

[0002] In recent years, with the development of electronic devices towards miniaturization and high integration, the demand for miniaturized, high-capacity and high-reliability multilayer ceramic capacitors (MLCC) is increasingly urgent, which requires thin layering of dielectric layers and multilayering of capacitors in process technology. Therefore, high-purity, ultra-fine, tetragonal barium titanate-based raw powder is one of the key technologies to achieve this goal.

[0003] Barium titanate is one of the main raw materials for preparing multilayer ceramic capacitors. However, due to the size effect of barium titanate, the lower the grain size, the lower the tetragonality (c / a), which leads to a decrease in the dielectric constant. To maintain a high dielectric constant, calcium can be doped into barium titanate, causing lattice distortion and improving the dielectric properties of the material, providing an important foundation for subsequent high-performance dielectric ceramics.

[0004] Currently, barium titanate powder can be synthesized by liquid phase method and solid phase method. Barium titanate powder prepared by liquid phase method (such as hydrothermal method) has small particle size and uniform distribution, but the cost is high and there are a large number of defects in the grain, which is not conducive to the preparation of high-reliability MLCC. The solid phase method for preparing barium titanate has simple process, low cost and good reliability, but the particles are large and the particle size distribution is uneven. There are patents reporting the use of solid phase method to prepare barium titanate-based dielectric raw powder. For example, patent document 1 (Chinese publication number CN113353974A), patent document 2 (Chinese publication number CN116283275A), patent document 3 (Chinese publication number CN114105190A), patent document 4 (Chinese publication number CN1841588A) and the like, but the particle size of some powders is large (>100 nm) and the particles are seriously agglomerated. Patent document 5 (Chinese publication number CN113121222A) uses phosphate as a dispersant and adds a combustion aid to grind barium carbonate and titanium dioxide respectively, then mixes and grinds again, and calcines to obtain barium titanate powder with a particle size of 90-220 nm. However, this process uses Na +dispersant, resulting in a decrease in powder purity. Patent document 6 (Chinese Publication No. CN 112266012A) also adopts separate sand milling of raw materials, followed by re-mixing sand milling and two-step calcination, obtaining a barium titanate powder with an average particle size of 80-220 nm and a c / a of about 1.009, but the process is relatively cumbersome and time-consuming. Patent document 7 (Chinese Publication No. CN 114105190A) mixes the raw materials together and then performs sand milling, calcination, to obtain a barium calcium titanate powder with an average particle size of 50-200 nm and a c / a higher than 1.008. This process uses 50-100 μm zirconium balls, and the sand milling conditions are harsh, and the powder is prone to agglomeration after calcination without dispersion treatment. Therefore, improving the dispersion uniformity of the powder and preventing particle agglomeration are very important in the preparation process of ultrafine powder. Some patents add dispersants to improve the dispersibility of the original powder, but the choice of dispersant has a great influence on the particle size and dispersibility of the barium titanate powder. SUMMARY

[0005] The purpose of the present application is to provide a calcium-doped barium titanate ultrafine powder with high tetragonality and uniform dispersion, as well as a preparation method and application thereof.

[0006] In a first aspect, the present application provides a preparation method for preparing a calcium-doped barium titanate ultrafine powder under alkaline conditions, comprising: (1) weighing barium carbonate powder, titanium dioxide powder and calcium carbonate powder as raw material powders according to the chemical formula of the calcium-doped barium titanate ultrafine powder (Ba 0.98 Ca 0.02 ) x TiO3, then adding water, a dispersant and ammonia water, mixing and performing first sand milling to obtain a first slurry, wherein x = 0.99-1.005; (2) drying, sieving and low-temperature calcining the obtained first slurry to obtain a first powder; (3) performing second sand milling on the obtained first powder, water, a dispersant and ammonia water to obtain a second slurry; (4) drying, sieving and high-temperature calcining the obtained second slurry to obtain a second powder; (5) sieving the obtained second powder, then adding an organic solvent to perform third sand milling to obtain a third slurry; (6) drying and sieving the obtained third slurry to obtain the calcium-doped barium titanate ultrafine powder.

[0007] In the present application, by adjusting the acidity and alkalinity of the slurry, the surface zeta potential of the raw material can be changed, the viscosity of the slurry can be reduced, and the uniformity of the dispersion of the raw powder can be ensured, which is beneficial to obtain the ultrafine powder with uniform dispersion. Specifically, the polyoxyalkylene compound is used as the dispersant in the present application, and the molecular weight of the dispersant is less than 3000. Compared with the traditional polyacrylic compound dispersant, the main chain length of the dispersant is reduced, and the polyfunctional comb structure is provided, the steric hindrance effect is enhanced, the agglomeration of the powder is effectively reduced, and the grain growth is effectively inhibited. Moreover, the alkaline aqueous solution is used in the present application. Because the surface zeta potential of the barium carbonate and the polyoxyalkylene compound in the alkaline solution (pH = 8-9) is negative (about -10 mV to -15 mV), while the surface zeta potential of the titanium dioxide is positive (about 13-15 mV) at this time, and in the alkaline solution, the absolute values of the zeta potentials of the barium carbonate and the titanium dioxide are both large (for example Figure 1 As shown in the figure, the potential test process includes: adding the barium carbonate into water and 2wt% dispersant (polyoxyalkylene amine salt), and then adjusting the pH to 3.6, 4.1, 7 (without adding ammonia water), 8, 9 and 10 by using acetic acid and ammonia water. Adding the barium carbonate into water and 2wt% dispersant (polyoxyalkylene amine salt), and then adjusting the pH to 7 (without adding ammonia water), 8, 9 and 10 by using ammonia water. Then the potential value is tested by using the NanoBrook instrument company. Therefore, the particles of the same raw material repel each other, while the particles of the barium carbonate and the titanium dioxide attract each other, so that the dispersion between different raw materials is more uniform, and therefore the calcium-doped barium titanate powder obtained by the present application has smaller particle size, uniform dispersion and less agglomeration. At the same time, high-purity anatase titanium dioxide is used as the raw material in the present application to improve the reaction activity, and the two-step sand milling and two-step calcination process can effectively improve the tetragonality of the powder.

[0008] Preferably, in step (1), the dispersant is a polyoxyalkylene compound with a short-chain comb structure, the functional group of which is polycarboxylic acid or amine; the molecular weight of the dispersant is less than 3000; and the amount of the dispersant added is not more than 2% of the mass of the raw powder. The first slurry is adjusted to be alkaline by adding ammonia water; preferably, the pH of the alkaline is 8-9. In the present application, the selection of the appropriate dispersant can effectively enhance the steric hindrance effect, which is beneficial to reduce the agglomeration of the powder and prevent the growth of the grain.

[0009] Preferably, in step (1), the purity of the barium carbonate powder, the titanium dioxide powder and the calcium carbonate powder is higher than 99%. The shape of the barium carbonate powder is needle-like, the length is 1-5 μm, and the specific surface area is 2-3 m 2 / g; The particle size of the calcium carbonate powder is 200-500 nm. The particle size of the titanium dioxide powder is 20-200 nm, and the specific surface area is 50-120 m 2 / g, and the anatase crystal phase accounts for more than 98%.

[0010] Preferably, in step (1), the mixing is ball milling, and preferably, the ball milling parameters include a ball milling speed of 200-400 r / min and a ball milling time of 1-6 h. The first sand milling parameters include that the zirconium balls used are 0.1-0.5 mm, the filling amount is 70-80%, the sand milling speed is 700-3000 r / min, and the sand milling time is 1-6 h. The average particle size of the raw material powder after the first sand milling is 20-80 nm.

[0011] Preferably, in step (2), the low-temperature calcination process conditions include that the temperature is raised to 700-800 ℃ at a rate of 3-10 ℃ / min, the temperature is raised to 850-900 ℃ at a rate of 3-5 ℃ / min, and the temperature is kept for 0.5-2 h to prevent crystal grain agglomeration and growth. The low-temperature calcination temperature has an effect on the particle size of the powder. If the temperature is too high, the particle size will increase.

[0012] Preferably, in step (3), the dispersant is a polyoxyalkylene compound with a short-chain comb structure, the functional group of the dispersant is polycarboxylic acid or amine, the molecular weight of the dispersant is less than 3000, the amount of the dispersant added is not more than 2% of the mass of the raw material powder, ammonia water is added to adjust the first slurry to be alkaline, and preferably, the alkalinity has a pH of 8-9. The second sand milling parameters include that the zirconium balls used are 0.1-0.5 mm, the filling amount is 70-80%, the sand milling speed is 700-3000 r / min, and the sand milling time is 1-6 h. Since the raw material powder is subjected to low-temperature calcination, a first powder of a mixed powder of Ca-doped BaTiO3 and Ba2TiO4 is prepared, at this time, the polyoxyalkylene compound is used as a dispersant, mainly utilizing its steric hindrance effect, effectively reducing the agglomeration of the powder, and further inhibiting the growth of crystal grains.

[0013] Preferably, in step (4), the high-temperature calcination process conditions include a temperature of 975-1050 ℃ and a holding time of 0.5-2 h, and preferably, the high-temperature calcination has a temperature rising rate of 3-10 ℃ / min. The high-temperature calcination temperature has an effect on the particle size of the powder. If the temperature is too high, the particle size will increase. In addition, the two-step calcination of steps (2) and (4) is beneficial to improve the c / a value.

[0014] Preferably, in step (5), the organic solvent is ethanol or water. The third sanding parameters include: the particle size of the zirconium ball used is 0.1-0.5 mm, the filling amount is 70-80%, the sanding speed is 700-3000 r / min, and the sanding time is 1-6 h.

[0015] In a second aspect, the present application provides the calcium-doped barium titanate superfine powder prepared by the above preparation method, wherein the particle size of the calcium-doped barium titanate superfine powder is 60-170 nm; the calcium-doped barium titanate superfine powder has high tetragonality, and the lattice parameter c / a is 1.005-1.009.

[0016] In a third aspect, the present application provides a ceramic dielectric material, which is prepared by the calcium-doped barium titanate superfine powder; preferably, the Curie peak of the ceramic dielectric material is 131-145 DEG C.

[0017] In a fourth aspect, the present application provides the application of the above calcium-doped barium titanate superfine powder in the preparation of a multilayer ceramic capacitor.

[0018] In a fifth aspect, the present application provides the application of the above ceramic dielectric material in the preparation of a multilayer ceramic capacitor.

[0019] The present application has the following beneficial effects: The present application improves the traditional solid phase method by mixing raw materials under alkaline conditions, and prepares a calcium-doped barium titanate superfine powder; compared with the hydrothermal method, the internal defects of the powder are reduced, which is beneficial to improve the reliability of the material. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Zeta potential spectrum of the particle surface after adding a dispersing agent to the raw material; Figure 2 XRD photo of the calcium-doped barium titanate powder prepared in the present application comparative example 3; Figure 3 SEM photo of the calcium-doped barium titanate powder prepared in the present application example 1; Figure 4 XRD photo of the calcium-doped barium titanate powder prepared in the present application example 1; Figure 5 Dielectric temperature curve of the calcium-doped barium titanate ceramic prepared in the present application example 1. DETAILED DESCRIPTION

[0021] The present application is further illustrated by the following examples, and it should be understood that the following examples are only used to illustrate the present application, but not to limit the present application.

[0022] The prepared calcium-doped barium titanate powder has a particle size of 60-170nm, high tetragonality, a lattice parameter c / a=1.005-1.009, and a Curie peak of the prepared ceramic at 131-145℃, and can be used as a dielectric material for preparing small, high-capacity and high-reliability multilayer ceramic capacitors.

[0023] The following example illustrates the method for preparing calcium-doped barium titanate ultrafine powder under alkaline conditions.

[0024] The barium carbonate, titanium dioxide and calcium carbonate are pre-dried. For example, drying at 100℃ for 2h. The purity of the barium carbonate, titanium dioxide and calcium carbonate is higher than 99%. The barium carbonate is needle-like with a length of about 1-5μm and a specific surface area of 2-3m 2 / g. The calcium carbonate has a particle size of 200-500nm. The titanium dioxide has a particle size of 20-200nm and a specific surface area of 50-120m 2 / g, and the anatase crystal form accounts for more than 98%.

[0025] The barium carbonate, titanium dioxide and calcium carbonate are mixed according to the stoichiometric ratio of (Ba 0.98 Ca 0.02 ) x TiO3(x=0.99-1.005), water, a dispersing agent and ammonia are added and mixed, and then the first slurry (or powder slurry) is obtained after first sand milling. The mixing is carried out in a planetary ball mill. The dispersing agent is a polyoxyalkylene compound with an amine functional group and a molecular weight lower than 3000. The dispersing agent is added in an amount of 0-2% of the mass of the mixed powder, but not zero. In the planetary ball mill, the ratio of material:ball:solvent is 1:2:4, and the planetary ball milling conditions are: ball milling speed of 200r / min and time of 1-6h. During sand milling, the solution pH is 8-9. Zirconium balls of 0.5mm are used for sand milling with a filling amount of 70-80%. The first sand milling conditions are: sand milling speed of 1800-3000r / min and sand milling time of 4-6h. After the first sand milling, the average particle size of the powder is 20-80nm.

[0026] The powder slurry is dried and passed through an 80-mesh screen, and then first-step calcination (low-temperature calcination) is carried out to prevent grain growth during pre-synthesis, and finally the first powder is obtained. If high-temperature calcination is directly carried out, the powder will be severely agglomerated. The first-step calcination process conditions are: heating at a rate of 5-10℃ / min to 700℃, heating at a rate of 3℃ / min to 850℃, and holding for 0.5-2h.

[0027] The first powder after calcination is sieved through an 80-mesh screen, water, dispersant and ammonia are added, and the second sand milling is performed to obtain a second slurry. The dispersant is a polyoxyalkylene compound with an amine functional group and a molecular weight of less than 3000. The dispersant is added in an amount of 0-2% by weight of the first powder, but not zero. During sand milling, the solution pH is 8-9. The zirconium balls used for sand milling are 0.5 mm, and the filling amount is 70-80%. The second sand milling conditions are as follows: the sand milling speed is 800-1000 r / min, and the sand milling time is 1-2 h.

[0028] The second slurry after the second sand milling is dried, sieved through an 80-mesh screen, and subjected to the second calcination (or high-temperature calcination) to synthesize ultrafine powder with high tetragonal phase, thereby obtaining a second powder. The second calcination process conditions are as follows: the temperature is increased to 975-1050°C at a rate of 5°C / min, and the temperature is maintained for 0.5-2 h.

[0029] The second powder after calcination is sieved through an 80-mesh screen, an organic solvent (such as ethanol) is added, and the third sand milling is performed to obtain a third slurry. During sand milling, the solution pH is 8-9. The zirconium balls used for sand milling are 0.5 mm, and the filling amount is 70-80%. The third sand milling conditions are as follows: the sand milling speed is 700-900 r / min, and the sand milling time is 1-2 h.

[0030] The third slurry after the third sand milling is dried and sieved through an 80-mesh screen to obtain the final calcium-doped barium titanate ultrafine powder.

[0031] The following examples are further provided to illustrate the present application in detail. It should also be understood that the following examples are only used to further illustrate the present application, and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application are within the scope of protection of the present application. The specific process parameters in the following examples are only one example in the appropriate range, i.e., those skilled in the art can make appropriate selection within the range according to the description herein, and are not limited to the specific values in the following examples.

[0032] Example 1 (1) The barium carbonate, titanium dioxide and calcium carbonate are dried at 100°C for 2 h, the barium carbonate, titanium dioxide and calcium carbonate are mixed according to the stoichiometric ratio shown in formula 1, water, 2wt% dispersant (polyoxyalkylene amine salt) and ammonia are added, the material:ball:solvent is 1:2:4, the slurry pH is 9, the barium carbonate particle size is about 1-5 μm, the calcium carbonate particle size is 200-500 nm, the titanium dioxide particle size is 20 nm, and the anatase crystal form accounts for more than 98%; (2) (Ba 0.98 Ca 0.02 ) x TiO3, x=1 formula 1; (3) The slurry is first mixed uniformly in a planetary ball mill at a rotation speed of 200 r / min for 6 h, and then a powder slurry is obtained after first sand milling at a rotation speed of 1800 r / min for 6 h; (4) The powder slurry is dried at 80℃, sieved through an 80-mesh screen, and subjected to first calcination; (5) The first calcination process conditions are as follows: heating at a rate of 3℃ / min to 700℃, heating at a rate of 3℃ / min to 850℃, and holding for 2 h, sieving the calcined powder through an 80-mesh screen, adding water, a dispersing agent (polyoxyalkylene amine salt), and ammonia water to adjust the pH to 9, and performing second sand milling at a rotation speed of 900 r / min for 2 h; (6) The powder after second sand milling is dried, sieved through an 80-mesh screen, and subjected to second calcination at a process condition of heating at a rate of 5℃ / min to 975℃ and holding for 2 h; (7) The powder after second calcination is sieved through an 80-mesh screen, ethanol is added, and third sand milling is performed at a rotation speed of 1000 r / min for 2 h, the powder after second sand milling is dried and sieved through an 80-mesh screen, and a final calcium-doped barium titanate ultrafine powder is obtained.

[0033] Example 2 This example 2 uses the same method as example 1, the difference is that x = 0.99 in formula 1.

[0034] Example 3 This example 3 uses the same method as example 1, the difference is that x = 0.995 in formula 1.

[0035] Example 4 This example 4 uses the same method as example 1, the difference is that x = 0.999 in formula 1.

[0036] Example 5 This example 5 uses the same method as example 1, the difference is that x = 1.005 in formula 1.

[0037] Example 6 This example 6 uses the same method as example 1, the difference is that the second calcination temperature is 1025℃ and the holding time is 2 h.

[0038] Example 7 This example 7 uses the same method as example 1, the difference is that the titanium dioxide is in rutile phase.

[0039] Example 8 Example 8 was prepared by the same method as Example 1, except that the first calcination was performed at a rate of 10°C / min to 700°C, then at a rate of 3°C / min to 850°C, and held for 0.5h,

[0040] Example 9 Example 9 was prepared by the same method as Example 7, except that in step (1), the titanium dioxide was in rutile phase, and the titanium dioxide particle size was 200nm.

[0041] Example 10 Example 10 was prepared by the same method as Example 9, except that in step (1), ammonia was added, and the slurry pH was 8.

[0042] Comparative Example 1 Comparative Example 1 was prepared by the same method as Example 9, except that in step (1), the titanium dioxide was in rutile phase, and the titanium dioxide particle size was 200nm; no ammonia was added, and the slurry pH was 7.

[0043] Comparative Example 2 Comparative Example 2 was prepared by the same method as Example 9, except that in step (1), the titanium dioxide was in rutile phase, and the titanium dioxide particle size was 200nm; acetic acid was added, and the slurry pH was 5.

[0044] Comparative Example 3 Comparative Example 3 was prepared by the same method as Example 9, except that in step (1), the titanium dioxide was in rutile phase, and the titanium dioxide particle size was 200nm; ammonia was added, and the slurry pH was 10. The ammonia was added to excess pH, and the surface potential of the barium carbonate powder and the titanium dioxide powder were both negative (see Figure 1 ), which caused the barium carbonate powder and the titanium dioxide powder to repel each other, which was not conducive to the preparation of pure-phase calcium-doped barium titanate ultrafine powder, as shown in Figure 2 .

[0045] The calcium-doped barium titanate powder was detected: The powder dispersion was observed by scanning electron microscopy (SEM), and the average particle size was calculated; the lattice parameters were detected and fitted by X-ray diffraction (XRD), and the c / a value was calculated.

[0046] Table 1 is the process parameters of Examples 1-9 and Comparative Examples 1-2:

[0047] Table 2 is the experimental results of Examples 1-9 and Comparative Examples 1-2: Average particle size (nm) c / a value Powder dispersion Example 1 64 1.005 ○ Example 2 109 1.0075 ○ Example 3 102 1.0088 ○ Example 4 74 1.0052 ○ Example 5 64 1.005 ○ Example 6 130 1.009 × Example 7 102 1.005 ○ Example 8 60 1.005 ○ Example 9 120 1.0075 ○ Example 10 70 1.0045 ○ Comparative Example 1 169 1.009 × Comparative Example 2 149 1.006 × Comparative Example 3 89 1.005 × : powder is well dispersed; X: powder is severely agglomerated or has too many broken particles.

[0048] From the results of Examples 1-5 and Figure 3 , Figure 4 it can be seen that when x is close to 1, the obtained calcium-doped barium titanate powder has a smaller particle size. From the comparison of the results of Example 1 and Example 6, it can be seen that increasing the calcination temperature increases the average particle size of the powder, but under the same dispersion conditions, the powder calcined at a high temperature is worse in dispersion. From the results of Example 1 and Example 9, it can be seen that when a titanium dioxide powder with a small particle size is used as the raw material, a finer calcium-doped barium titanate powder can be obtained. From the comparison of Comparative Example 1, Comparative Example 2, and Example 9, it can be seen that under the same raw powder, sanding conditions, and calcination conditions, adjusting the pH value of the slurry shows that in an alkaline slurry, a calcium-doped barium titanate powder with a smaller particle size can be obtained.

[0049] The powder of Example 1 was pressed into a tablet and sintered to obtain a ceramic wafer, which was coated with silver on both sides, and then subjected to dielectric temperature testing. The Curie peak of the material at 1 kHz is above 140°C (as shown in FIG. 1), which provides a more optimal raw material basis for the preparation of ultra-fine ceramic formula powder with a wide temperature stability. Figure 5 The ceramic wafer obtained by pressing and sintering the powder of Example 1, coating it with silver on both sides, and then calcining it was subjected to dielectric temperature testing. The Curie peak of the material at 1 kHz is above 140°C (as shown in FIG. 1), which provides a more optimal raw material basis for the preparation of ultra-fine ceramic formula powder with a wide temperature stability.

Claims

1. A method for preparing calcium-doped barium titanate ultrafine powder under alkaline conditions, characterized in that, The method comprises the following steps: (1) The formula of calcium-doped barium titanate superfine powder is (Ba 0.98 Ca 0.02 ) x TiO3. Barium carbonate powder, titanium dioxide powder and calcium carbonate powder are weighed as raw material powders, and then water, dispersant and ammonia are added and mixed. After first sand milling, a first slurry is obtained, wherein x = 0.99-1.

005. (2) drying, sieving and low-temperature calcining the obtained first slurry to obtain a first powder; (3) performing second sand milling on the obtained first powder, water, a dispersing agent and ammonia water to obtain a second slurry; (4) drying, sieving and high-temperature calcining the obtained second slurry to obtain a second powder; (5) sieving the obtained second powder, adding an organic solvent and performing third sand milling to obtain a third slurry; (6) drying and sieving the obtained third slurry to obtain the calcium-doped barium titanate superfine powder.

2. The production method according to claim 1, characterized by, In step (1), the dispersing agent is a polyoxyalkylene compound with a short-chain comb structure, and the functional group thereof is polycarboxylic acid or amine; the molecular weight of the dispersing agent is less than 3000; and the amount of the dispersing agent added is not more than 2% of the mass of the raw material powder. The first slurry is adjusted to be alkaline by adding ammonia water; preferably, the pH of the alkaline is 8-9.

3. The production method according to claim 1 or 2, characterized by, In step (1), the purity of the barium carbonate powder, the titanium dioxide powder and the calcium carbonate powder is higher than 99%. The barium carbonate powder has a needle shape, a length of 1-5 μm, a specific surface area of 2-3 m 2 / g; The particle size of the calcium carbonate powder is 200-500 nm. The titanium dioxide powder has a particle size of 20-200 nm, a specific surface area of 50-120 m 2 / g, and the anatase crystal form accounts for more than 98%.

4. The production method according to any one of claims 1 to 3, characterized by, In step (1), the mixing is ball-milling mixing; preferably, the parameters of the ball-milling mixing include a ball-milling rotating speed of 200-400 r / min and a time of 1-6 h. The parameters of the first sand milling include a zirconium ball with a particle size of 0.1-0.5 mm and a filling amount of 70-80%, a sand milling rotating speed of 700-3000 r / min and a sand milling time of 1-6 h. The average particle size of the raw material powder after the first sand milling is 20-80 nm.

5. The production method according to any one of claims 1 to 4, characterized by, In step (2), the process conditions of the low-temperature calcining include a temperature rising rate of 3-10 ℃ / min, a temperature rising rate of 3-5 ℃ / min, a temperature of 700-800 ℃, a temperature of 850-900 ℃ and a holding time of 0.5-2 h.

6. The production method according to any one of claims 1 to 5, characterized by, In step (3), the dispersing agent is a polyoxyalkylene compound with a short-chain comb structure, and the functional group thereof is polycarboxylic acid or amine; the molecular weight of the dispersing agent is less than 3000; the amount of the dispersing agent added is not more than 2% of the mass of the raw material powder; the first slurry is adjusted to be alkaline by adding ammonia water; and preferably, the pH of the alkaline is 8-9. The parameters of the second sand milling include a zirconium ball with a particle size of 0.1-0.5 mm and a filling amount of 70-80%, a sand milling rotating speed of 700-3000 r / min and a sand milling time of 1-6 h.

7. The production method according to any one of claims 1 to 6, characterized by, In step (4), the process conditions of the high-temperature calcining include a temperature of 975-1050 ℃ and a holding time of 0.5-2 h; preferably, the temperature rising rate of the high-temperature calcining is 3-10 ℃ / min.

8. The production method according to any one of claims 1 to 7, characterized by, In step (5), the solvent is water or ethanol, and the parameters of the third sand milling include a zirconium ball with a particle size of 0.1-0.5 mm and a filling amount of 70-80%, a sand milling rotating speed of 700-3000 r / min and a sand milling time of 1-6 h.

9. The calcium-doped barium titanate ultrafine powder prepared by the preparation method according to any one of claims 1-8, characterized in that, The particle size of the calcium-doped barium titanate superfine powder is 60-170 nm; and the calcium-doped barium titanate superfine powder has high tetragonality, and the crystal lattice parameter c / a is 1.005-1.

009.

10. A ceramic dielectric material, characterized by, The ceramic dielectric material is prepared by using the calcium-doped barium titanate superfine powder of claim 9; preferably, the Curie peak of the ceramic dielectric material is between 131 and 145 ℃.

11. Use of the calcium-doped barium titanate superfine powder of claim 9 in the preparation of a multilayer ceramic capacitor.

12. Use of the ceramic dielectric material of claim 10 in the preparation of a multilayer ceramic capacitor.

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