Preparation And Characterization Of CCTO@SrTiO₃@ZBSO Composite Powders And Ceramics

Compared with BaTiO3ceramics, the CaCuaTi4O12(CCTO) is a well known non-ferroelectric material with high and nearly stable dielectric constant, which has the potential medium materials for supercapacitor. However, the giant dielectric constant of CCTO with high dielectric loss limits its practical value. According to the IBLCs model, the dielectric loss of CCTO can be reduced by improving the insulating properties of the grain boundary. So the idea of this paper is, first, coating a modifier of SrTiO3with well insulating on the surface of mono-disperse CCTO powders by settling and separating. The sintering activity of CCTO@SrTiO3ceramics was improved by further coating the sintering aid of ZBSO as the second layer, in order to reduce the dielectric loss of CCTO ceramics with good density in lower sintering temperature.We had studied the influence of reactant concentration, calcination temperature on the particle size of CCTO powders, which was prepared by oxalate co-precipitation method. In addition, the CCTO powders was treated by settling and separating, which acted as the core with well dispersion and morphology, and CCTO ceramics still had high dielectric constant. The CCTO powders were coated with two layers, the first layer was a modifier of SrTiO3and layer was the sintering aids of ZBSO. The purpose of coating the insulation layer on CCTO powders was to reduce the dielectric loss of ceramic. The second layer sintering aids were further to improve the density of ceramic with lower sintering temperature. We further research the effect of SrTiO3and ZBSO coating amount on the phase composition and microstructure of CCTO powders and ceramics and its dielectric properties. The CCTO@@SrTiO3@ZBSO ceramics with high density were obtained, laying the foundation for improving the dielectric properties of the CCTO based ceramic.The main content and conclusions are as follows:1. The CCTO powders with good dispersity were prepared by oxalate co-precipitation method, the effect of reactant concentration and calcination temperature on the phase composition and morphology of powders, the microstructure and dielectric properties of ceramics after settling and separating were studied. The CCTO powders (～1.0μm) calcined at950℃with good dispersity were obtained after settling and separating, when the concentration of H2C2O4and Cu2+are2.6mol/L and0.8mol/L, respectively. The mean sizes of CCTO powders of440nm,1μm and>1μm were obtained after settling and separating, respectively. The activity of powders was reduced, which resulted in the increase of sintering temperature and density by increasing particles sizes of CCTO. The dielectric loss of CCTO is high to0.17. Thus, it is important to coat a modifier on the surface of CCTO powders to reduce its high dielectric loss.2. The modifier of SrTiO3was coated on the surface of CCTO powders (～1μm) obtained above by sol-gel method. The effect of different coating amount of SrTiO3, sintering temperature on the phase structure, microstructure and dielectric properties of CCTO ceramic were studied. Studies have shown that the CCTO@SrTi03powders with " core-shell" structure were obtained. The grain sizes and dielectric constant of ceramics reduced gradually with more porosity, and the stability of dielectric constant was improved by increasing the coating amount of SrTiO3. The grain sizes of CCTO ceramics was greater than2μm sintered at1000℃, which meant that the solid solution was formed between CCTO and SrTiO3.Thus it is necessary to coat sintering aids on the surface of CCTO@SrTiO3to obtain a dense ceramics in lower sintering temperature.3. The sintering aids of ZBSO were coated on the surface of CCTO@SrTiO3powders by the sol-gel method. The effect of coating amount of ZBSO, sintering temperature on the phase structure, microstructure and dielectric properties of ceramic were studied. Studies have shown that the CCTO@SrTiO3@ZBSO powders with " core-shell" structure were obtained. The dense of ceramics was obviously improved by increasing the amount of ZBSO. When the coating amount of ZBSO is8%sintered at lower temperature of960℃, the ceramics had the best denseness, as well as the stability of the dielectric constant is enhanced within a certain frequency range with a good density.