Micro-grained BaTiO₃ PTCR Ceramic Materials Preparaed From Nanopowders

The ceramics preparaed by barium titanate which have prominent positive temperature coefficient is called PTC material. It's applied to a variety of functional modules as overload protection device in electronic circuit due to its advantages like simple preparation, wide use and high reliability, it has been a hot topic in the study of functional material for a long time. With the rapid development of science and technology, higher demands are required, just like miniaturization, high voltages, high reliability and so on. Material high voltages and large current shock characteristics could be improved by micro crystallization method. In order to make the grain of PTC smaller, this paper focuses on barium titanate nanopowders which is used as raw material and synthesizes PTC ceramics which has excellent electrical properties and micro crystallization microstructure. And it analyzes the influence on the microstructure and electrical properties of doping modification and sintering process. This paper focuses on the influence of different doping material for micro crystallization and electrical properties, mainly five aspects in different dosages are included: donor, acceptor, Curie point of moving agent, Ca and glass phase. Then it analyzes the experimental results with theoretical analysis. It could be concluded that some related rules of different doping to the change of average grain size of ceramics material and the optimal proportion can be gotten. Then according to the experimental results, sintering process which includes sintering methods, sintering temperature and holding time, is considered about the influence on microstructure and electrical properties of PTC. And we can get some related rules about the influence on the change of grain size. Then the optimal sintering curve can be gotten.At last, optimal performance of PTC can be achieved according to the optimal proportion and the optimal proportion of sintering process. Its resistivity is about 4900 ?·cm with Tc at about 118.3 °C, resistivity jumps of 8.2×103, and its average grain size reaches about 1 ?m. And it is very uniform and compact and could stand more than 400V/mm voltage strength. With testing 10 thousand times of large current shock, it's still working which meets the practical requirements. We can achieve goals.