The effects of TiO₂ contents (or thickness of TiO₂ surface layer) in TiO₂(Ti) powder and the grain size of Ti powder (or interparticle spacing of Ti particles) on the PTCR characteristic of the (Ba, Sr)TiO₃ compact added with TiO₂(Ti) or Ti, which were sintered in vacuum at 1623K for 3.6ks, were investigated.
The results obtained were as follows; (1)With increasing TiO₂ content of the TiO₂(Ti) from 12.5mass% to 25 and 37.5mass%, the range of metallic Ti content in TiO₂(Ti) needed for the development of PTCR characteristic became 1.7 times larger at maximum. (2)For the sintered compact added with 2μm Ti powder, the range of Ti content needed for the development of PTCR characteristic was larger than that of the compact with 18μm Ti powder. (3)The above phenomena seemed to be due to the homogenization of oxygen ion concentration in (Ba, Sr)TiO₃ particles which are caused by increasing thickness of TiO₂ layer or decreasing interparticle spacing of Ti particles.