Research And Preparation Of Ring Varistors

Multifunction SrTiO3 ceramic varistor has the advantages over ZnO varistor in many electric function . It's high-frequence noise absorption, absorption of noise caused by rapid rise of front and self-reset function have widespread application in imput of supply ,for absorption of inductive load switching surge voltage and for protection of two-way thyristor switching device ,bypass capacitors ,micro-machines and the others.Research of this thesis include two parts mainly, first part include the preparation of SrTiO3 powder materials by sol-gel process and solid phase synthesis process. The second part , on the base of strontium titanate powder materials prepared , SrTiO3-based capacitor-varistor double function ceramic were fabricated by the conventional ceramic process.First of all, prepare SrTiO3 powder materials by sol-gel process and solid phase synthesis process. Stir time, gel time, gel temperature, heat treat temperature and so on are researched in sol-gel process. The method of grind, Ti/Sr ratio are researched in solid phase synthesis process.Second, on the base of strontium titanate powder materials prepared , SrTiO3-based double function ceramic were fabricated by the conventional ceramic process. For SrTiO3-based double function ceramic, it is well know that the suitable grain size, the semiconducting of grain and the insulating of grain boundary are important keys. The growth and semiconducting of grains are influenced by a lot of factors , such as the type and contents of dopants , Ti/Sr ratio , sintering temperature and so on . All of the above factors are relevant and restricted with each growth . Therefore, in this paper the effect of the above factors were studied .Finally, the sample was characterized by XRD,SEM methods.