Preparation And Electric Properties Of Semiconducting BaSnO₃ Ceramics

In this thesis, preparation techniques and electric properties about semiconducting BaSnO₃ ceramics are researched. Good samples are prepared by using BaCO₃ and SnO₂ as starting materials, a few of purities as additives, donors and acceptors, and conventional solid-state reaction method. It provides a method to overcome the problem about the difficulty of BaSnO₃ ceramics sintering. The materials prepared have high density over 97% theoretical value, good grains with size of 4～10μm and average diameter 8μm, nice structure and without other phase between grain and grain boundary.The effect of Na₂CO₃, Li₂CO₃ and Mn(NO₃)₂ doping as acceptors to BaSnO₃ ceramics is study detailedly. Result indicate that Na₂CO₃ or Li₂CO₃ doping solely to improve the grain boundary barrier perform ineffectively, while effectively doping with Mn(NO₃)₂ and better with more quantities, but effect the grain conduction badly when dope Mn(NO₃)₂ too much. Using an appropriate quantity and ratio can get a better result, i.e. apparent material resistivity 3.3×10⁶Ω·cm and grain resistivity 4.3Ω·cm, apparent dielectric coefficientεr=1.9×10⁴(1KHz) and loss factor less than 0.4 between 1KHz to 6MHz. The problem of grain boundary barrier improvement in semiconducting BaSnO₃ ceramics is basically resolved.Sb₂O₃ dopant have powerful performance as additive to BaSnO₃ ceramics sintering, can improve the material density, and reduce the temperature for sintering, even make material becoming ceramics at 1350℃with large quantity. Experiment result indicate that increasing Sb2O3 content can compensate the acceptors existing in grain boundaries and reduce the barrier height. The sintering temperature is a key factor to performance of BaSnO₃ ceramics. With the temperature reducing, the worse sintering effect will lead to the bad electric performance. samples with purity grain phase, ideal structure and good electric property can be attained with 1350℃temperature. In addition, secondary heat treatment for samples have no effect to increase the grain boundary barrier of semiconducting BaSnO₃ ceramics indicated by...