Preparation And Characterization Of Barium Titanate Based Ceramics With Temperature Stability

This dissertation uses the traditional solid phase method and sol-gel method to prepare nanosized and submicron dopant doped barium titanate?BaTiO₃?based dielectric ceramic material,a temperature stable,high permittivity X8R barium titanate based dielectric ceramic materials sintered in medium temperature is obtained.Which means great significance for the miniaturization of high temperature stabilized multilayer ceramic capacitors?MLCC?.Using the traditional solid phase method and sol-gel method respectively for Bi-Ti-Zn-B sintering agent prepared by adding submicron and nano Bi-Ti-Zn-B in the original X8R system in barium titanate based sintering agent,mainly studied the effect of nano assisted sintering agent and mixed sintering agent of barium titanate nano X8R system and help sintering agent and sub micron help synergistic effect of the sintering agent,the nanometer additives and mixed sintering agent can effectively reduce the sintering temperature and optimization of barium titanate based dielectric ceramic dielectric properties.The nanometer and submicron Bi-Ti-Zn-B sintering aid the doping ratio of 2:1 has the best performance in 1150? was prepared under high permittivity(?_20?=3460)and low loss?tan?=1.1%?X8R barium titanate based dielectric ceramic materials.Based on the percolation theory,Elemental silver is doped to barium titanate based dielectric ceramic material to form conductor-dielectric composites.The dielectric constant of the composite decreases first and then increases with the increasing doping amount of the silver.When the doping amount of silver is 2mol%,the best performance with low-cost is obtained:?_20?=4376,tan?<1.5%,and its temperature stability meets the standard requirement of EIA-X7R.We prepare nanometer giant dielectric material:copper bismuth sodium titanate(Na_0.5Bi_0.5Cu₃Ti₄O₁₂,NBCTO)via sol-gel method,and doped in X8R type barium titanate dielectric ceramic system in order to improve the dielectric constant of the system.However doped barium titanate dielectric ceramic's dielectric constant decreased and temperature stability deteriorated.In view of this phenomenon,we use complex impedance spectrum test on giant dielectric material NBCTO,and found that the giant dielectric mechanism of NBCTO is due to the interfacial polarization internal barrier layer capacitance;and the decomposition temperature of NBCTO is low,which lead to decomposition of NBCTO at the sintering temperature of barium titanate.Moreover,decomposition product diffuses into BaTiO₃ grains,resulting in destruction of"core-shell"structure in barium titanate grains.Therefore,NBCTO doped barium titanate based dielectric ceramics not only deteriorate the original temperature stability of barium titanate system,but also reduces the dielectric constant of the system.