Preparation Of Double Layers Of Alumina And Sintering Aid Coated Barium Zirconate Composite Particles And The Research On The Sintering Character Of The Ceramics

Compared with the traditional BaTiCO3ceramics, the BaZrxTii-xO3ceramics have great dielectric constant and excellent temperature stability, so it has the potential to prepare the supercapacitors. The multilayer dielectric ceramic used to made super capacitor were ultrathin, the problem of improving the voltage resistance was the key. However, if the BaZrxTii1-xO3ceramics was used to prepare the supercapacitors, the voltage resistance should been enhanced and the dielectric loss should been decreased. So the idea of this paper is, first, coating the stable AI2O3with insulation characteristic on BaZrxTi1-xO3powders to improving the voltage resistance; further coating the sintering aid as the second layer to improve the sintering activity.For research on the coating process and the influence of the coating layers on the composition, the structure and the morphology of powders materials and ceramics materials; The BaZrO3with high sintering temperature was as the object of study. In addition, the BaZrO3was easily synthesized and got monodisperse and sphere powders, so it was acted as the core. The BaZrO3powders were coated with two layers, the first layer was AI2O3, the second layer was sintering aid(T-S-0and Zn-B-Si-O). The first layer of AI2O3was not only improve voltage resistance, but also acted as the barrier layer. The second layer of sintering aid improved the density of ceramics. The pH was determined by the Zata potential when the composite particles were prepared by precipitation. The coated powders were characterized by XRD, SEM, EDX energy spectrum and XPS. The effects of A12O3and sintering aid (T-S-0and Zn-B-Si-O) coating amount on the microstructure and phase constitution of BaZrO3powders and ceramics were investigated. The aim was to obtain the BaZrO3based ceramics poeders coated with the layer of AI2O3and the compact ceramics, laying the foundation for improving the voltage resistance of BaZrxTi1-xO3based ceramics.The research content, see as follows:1、The BaZrO3powders was prepared by a synthetic method with one step in water phase under atmosphere pressure. The effect of the concentrations of NaOH and the concentrations of reactants on the partical size of BaZrO3powders was investigated. The partical size controllable synthesis of BaZrO3powders was achived. The BaZrO3@Ai2O3powders were prepared by deposition. The pH of precipitation was investigated. The different capability between modified-coate and uncoated BaZrO3powders were also investigated, such as phase constitution, microstructure and composition. The results showed that: the particle size of BaZrO3powders decreased with increasing the concentration of NaOH and the concentrations of reactants. In the precipitation process NH3·H2O was acted as the preparation agent and A1(NO3)3·9H2O was acted as alumina source for the preparation of BaZrO3@AlaO3composite power. The results showed that: the optimal concentration of Al3+was1mol/L; pH value was9;lower reaction temperature(25℃) was conducive to Al(OH)3deposition on the surface of BaZrO3powders. The obtained BaZrO3@Al2O3composite powers were still momodisperse and sphere.2、The BaZrO3@Al2O3composite powders were coated by Ti-Si-O(TSO) sintering aid layer via hydrolysis-precipitation method. The double coated powders of BaZrO3@Al2O3@TSO could be observed by XRD, SEM and EDX. The pH value of hydrolysis-precipitation was investigated. The different capability between modified-coate and uncoated BaZrO3@Al2O3powders with TSO sintering aid were also investigated, such as phase constitution, microstructure and composition. The effect of the coating amount of AI2O3and TSO sintering aid on the microstructure and phase constitution of composite ceramics were also investigated. The results showed that: the optimum pH value of hydrolysis-precipitation was9. TSO sintering aid uniformly and continuously coated on the surface of BaZrO3@Al2O3powders. The density of ceramics increased firstly and then decreased with increasing the coating amount of AI2O3and TSO sintering aid. When the covering amount of AI2O3was4wt%and TSO was6wt%, the high-density BaZrO3@Al2O3@TSO ceramics could be obtained at1350℃, the sintering temperature got significant reduction. Because AI2O3with TSO formed low melting glass, the grain size of BaZrO3@Al2O3@TSO ceramics increased compared to the corresponding powers. The voltage resistance layer of AI2O3was destroyed.3、The BaZrO3@Al2O3composite powders were coated by Zn-B-Si-O (ZBSO) sintering aid layer via sol-gel method. The double coated powders of BaZrO3@Al2O3@ZBSO were obtained. The coated surface was smooth and continuous. The different capability between modified-coate and uncoated BaZrO3@Al2O3powders with ZBSO sintering aid were also investigated, such as phase constitution, microstructure and composition. The effect of the coating amount of AI2O3and ZBSO sintering aid on the microstructure and phase constitution of composite ceramics were also investigated. The results showed that: The densification of BaZrO3@Al2O3@ZBSO ceramics sintering at13OO℃increased first and then decreased with the increase of the covering amount of ZBSO. With the AI2O3layer, the effect of ZBSO sintering aid for BaZr03@Al203@ZBSO ceramics was obvious, and the grain size of BaZrO3@Al2O3@ZBSO ceramics kept the same with the corresponding powers. The AI2O3acted as a barrier coat for the ZBSO sintering aid. The voltage resistance layer of AI2O3could not be destroyed by ZBSO sintering aid.