CN-121974679-A - High-crystallinity perovskite nanocrystalline powder prepared by oxalate method and two-stage calcination

CN121974679ACN 121974679 ACN121974679 ACN 121974679ACN-121974679-A

Abstract

The invention discloses high-crystallinity perovskite nanocrystalline powder prepared by an oxalate method and two-stage calcination. The chemical general formula of the powder is Ba 1‑x Me x TiO 3 (x is more than or equal to 0 and less than or equal to 0.2), me is one or more of Ca, sr and other elements, the average grain size is 30-120 nm, the grain size discrete coefficient s is less than or equal to 0.4, and the powder has high tetragonal distortion ratio (c/a). The method adopts a novel oxalate method, namely, firstly complexing a titanium source with oxalic acid in ethanol, adding a surfactant, then reacting with barium/Me salt solution, curing to obtain an oxalate precursor, and carrying out two-stage calcination after cleaning, ball milling and refining, namely, decomposing and initially forming phases at 580-800 ℃, and then completing crystallization optimization at 900-1200 ℃. The method solves the problems of coarse grains, uneven distribution or many defects of the traditional method, realizes the controllable preparation of superfine, uniform and high-crystallinity powder, and is particularly suitable for manufacturing miniaturized, high-capacity and high-reliability multilayer ceramic capacitor (MLCC) dielectric layers.

Inventors

WANG XIAOHUI
WANG XINJIE
ZHAO PEIYAO
CHENG XU
ZHEN YICHAO

Assignees

清华大学

Dates

Publication Date: 20260505
Application Date: 20251225

Claims (10)

1. The high crystallinity perovskite nanocrystalline powder has a chemical general formula of Ba 1-x Me x TiO 3 , wherein x is more than or equal to 0 and less than or equal to 0.2, and Me is one or more selected from Ca, sr, cd, cu, mg, zn, ni, la, bi, Y, ho and Ag.
2. The titanate perovskite nanocrystalline powder according to claim 1, wherein the average grain size of the titanate perovskite nanocrystalline powder is 30 nm-120 nm, the grain size dispersion coefficient s is less than or equal to 0.4, and the perovskite nanocrystalline powder has a perovskite crystal structure.
3. The titanate perovskite nanocrystalline powder according to claim 1 or 2, wherein the tetragonal distortion ratio c/a of the titanate perovskite nanocrystalline powder is not less than 1.002.
4. A method for producing the titanate perovskite nanocrystalline powder according to any one of claims 1 to 3, comprising the steps of: s1, preparing a precursor, namely preparing a titanium oxalic acid complex, adding a salt solution containing barium ions and Me ions into the solution of the titanium oxalic acid complex for reaction, and curing to obtain a Ba 1-x Me x TiO(C 2 O 4 ) 2 ·nH 2 O precursor precipitate, wherein n=1-8; s2, ball milling treatment, namely cleaning and drying the precursor precipitate obtained in the step S1, dispersing the precursor precipitate in a solvent, and performing ball milling to obtain slurry; And S3, two-stage calcination, namely, calcining the precursor powder obtained by drying and sieving the slurry obtained in the step S2, wherein the calcination process comprises the steps of heating to 580-800 ℃ at 5-15 ℃ per min, preserving heat for 1-5h, heating to 900-1200 ℃ at 5-40 ℃ per min, and preserving heat for 0.5-3h to obtain the titanate perovskite nanocrystalline powder.
5. The method according to claim 4, wherein in the step S1, the titanium oxalic acid complex is prepared according to the following steps: mixing an ethanol solution of tetrabutyl titanate with an ethanol solution of oxalic acid, and adding a surfactant to form a titanium oxalic acid complex solution.
6. The method according to claim 5, wherein the concentration of the ethanol solution of tetrabutyl titanate is 0.1 to 1.0 mol/L, the concentration of the ethanol solution of oxalic acid is 0.1 to 1.0 mol/L, and the molar ratio of oxalic acid radical to titanium ion is (2 to 2.2): 1; The surfactant is at least one selected from polyethylene glycol, polyvinylpyrrolidone, diethylene glycol, polyacrylic acid-maleic anhydride, ammonium polyacrylate, sodium dodecyl sulfate, sucrose fatty acid ester and sodium stearyl lactate.
7. The method according to any one of claims 4 to 6, wherein in the step S1, the curing temperature is 40 to 80 ℃ and the curing time is 2 to 12 hours.
8. The method according to any one of claims 4 to 7, wherein in the step S2, the solid content of the ball milling is 10% -35%, the grinding medium is zirconia balls, the ball milling speed is 200-400 r/min, and the ball milling time is 1-6h.
9. The method according to any one of claims 4 to 8, wherein in step S2, the solvent is water, ethanol or isopropanol.
10. A multilayer ceramic capacitor whose dielectric layer comprises the titanate perovskite nanocrystalline powder according to any one of claims 1 to 3.

Description

High-crystallinity perovskite nanocrystalline powder prepared by oxalate method and two-stage calcination Technical Field The invention relates to high-crystallinity perovskite nanocrystalline powder prepared by an oxalate method and two-stage calcination, belonging to the technical field of electronic ceramic materials. Background With the continuous progress and development of electronic information technology, the demand for miniaturization of electronic components is increasing. The multilayer ceramic capacitor (MLCC) has the advantages of high voltage resistance, high temperature resistance, high capacity, high reliability and the like, and is the passive electronic component with the highest production value at present. In particular, in recent years, the explosive growth of global AI computing power brings about a serious energy challenge, the stability of an electric power system has become a core factor for restricting the full release of computing power, the MLCC plays a role in stabilizing and filtering in a power supply network, and the performance directly determines the operation precision, stability and service life of an AI chip. Accordingly, the evolving demands place increasing demands on miniaturization, high capacity, high reliability, and low cost of MLCCs. Common ceramic materials of the ABO 3 type perovskite structure include BaTiO3、CaTiO3、Ba1-xCaxTiO3、Ba1-xSrxTiO3、Ba1-x-yCaxSryTiO3 and the like. Perovskite ceramic materials are currently the most widely used dielectric matrix materials due to their excellent dielectric, ferroelectric properties. The advantages of barium titanate, which has a high dielectric constant and a low loss rate, make it suitable for manufacturing high-capacity capacitors. However, it undergoes transition from tetragonal phase to cubic phase at curie temperature, and dielectric constant exhibits a maximum value, forming a sharp curie peak, which makes its temperature stability poor, which is disadvantageous for practical use. Therefore, solid phase doping or chemical coating is often used to smooth the dielectric constant-temperature curve, so that the dielectric constant is kept relatively stable in a wider temperature range, and the stable temperature range is expanded. With the continued miniaturization of electronic components, dielectric layer thicknesses have been further thinned from a few microns to submicron levels. In order to ensure the reliability of the device, each layer of medium usually needs to contain 5-7 crystal grains, so that the requirement of grain refinement and homogenization is imposed on the matrix material. The initial particle size of the matrix powder needs to be controlled below 120 nm so as to meet the design requirement of the multilayer ceramic capacitor. However, when the grain size is reduced to the nanometer level, its polarization ability is significantly reduced due to the influence of the size effect, resulting in a decrease in dielectric constant. The high tetragonal phase has few crystal defects, regular atomic arrangement and excellent performance, but generally has a large crystal grain size. In order to maintain higher capacitance performance under a fine-grain structure, it is necessary to ensure that the titanate perovskite nanocrystals have higher crystallinity and a high tetragonal distortion ratio (c/a). Therefore, how to realize the preparation of powder with ultra-fine and uniform grains, high tetragonality and high crystallinity for the dielectric material applied to the highly reliable and miniaturized MLCC is a key target of the current material design. The main synthesis approaches at present mainly comprise methods such as a solid phase method, a hydrothermal method and the like. The solid phase method is prepared by mixing A-site element carbonate with raw material powder such as titanium dioxide and reacting at high temperature, and has the advantages of simple process, high reliability, convenient industrial continuous production and low cost. However, the reaction requires a long high-temperature treatment, resulting in a significant increase in energy consumption, while the product particles are large in size, unevenly distributed, and large in discrete coefficient (s=standard deviation/average value). The hydrothermal method is to generate nano-scale particles by utilizing the reaction of A-site element salt and titanium salt in a high-temperature high-pressure solution, has high product purity and crystallinity, can synthesize small-size grains, but has higher synthesis cost and complex process flow, and has a large number of hydroxyl, proton and carbonate defects in the grains in the preparation process of the hydrothermal method, so that the powder density is reduced, the tetragonal distortion is inhibited, and the capacity and the reliability of the prepared MLCC device are reduced. In view of the limitations of the above methods in particle refinement, grain uniformity, and defect control, the