Sol - Gel Process And Strontium Titanate Materials And Dual-function Devices

The study described in this thesis consists of two parts: the preparetion of nanocrystalline powder materials by sol-gel process and the preparation of the SrTiOs-based capacitor-varistor double function ceramics device.First, strontium titanate nanocrystalline powder materials were prepared from Sr(NO3)2 -Ti(OC4H9)4 -HbO- Ct^COOH system by the sol-gel method. In order to obtain the strontium titanate nanocrystalline powers materials with small grain, high purity and homo- geneous grain size distribution, the effect of water, waiter-free acetic acid, gel temperature, heat treat temperature and so on were researched. The results of DSC-TG and XRD(X-ray diffracton) showed that prepared gels began to transform into the strontium titanates with perobskite-type cubic phase at 600癈 by a heat treatment and the reaction was completed proximately at 800癈. The grain sizes were smaller than 51.78nm using Scherrer's formula. The results of transmission electron microscopy(TEM) showed that the grain of strontium titanate powder prepared was spherical and the grain sizes distribution were homogeneous.Second, SrTiOS-based double function ceramic was achieved with prepared strontium titanate nanocrystalline powder materials by single-fired process. Grain size, the semiconducting of grain and the insulating of grain boundary were keys to the single-fired process of preparation of SrTiO3-based double function ceramic, and affected directly the dielectric and varistor properties. But the grain growth, grain semiconduction and grain boundary insulation were influenced by many factors, such as the type and contents of dopants, sintering temperature and so on. Therefore, in this thesis the effect of the restore sintering temperature, the oxygenize temperature, the donor and acceptor dopant on the dielectric and varistor properties of devices were studied. With SEM, the microstructure of SrTiO3-based double function ceramic was analyzed.