Abstract: An analysis based on the double Shottcky barriers model at the grain boundaries of donor dopant BaTiO₃ ceramics indicated that the drift and diffusion conducting mechanism of free electrons might be substituted by a simple thermal excitation mechanism in the case of low density acceptor states at the grain boundaries; the relationship of equivalent resistivity dependence on temperature was derived and fitted with values; the results showed that the resistivity of PTC ceramic materials in the paraelectric phase was linear over a rather wide range of temperature.
The results of experimental investigation on PTC ceramic materials based on (Ba-Sr)TiO₃ showed that the density of the acceptor states at grain boundaries could be controlled by the modifier of composition and process, and the PTC ceramic materials with excellent linearity in the temperature region of about 120℃ could be prepared. The experimental results were also discussed.