Effect of atmosphere on the PTCR characteristics of porous (Ba,Sr)TiO3 ceramics

Porous and fine-grained (Ba,Sr)TiO3 ceramics were fabricated by adding part ially oxidized Ti powders. During heating and cooling, the electrical resis tance was measured in air, O-2, N-2, and H-2 atmospheres and in H, followed by air atmosphere. The effect of atmosphere on the PTCR characteristics an d the role of oxygen on the grain-boundaries in the PTCR characteristics we re investigated. The porous (Ba,Sr)TiO3 ceramics showed a large PTCR effect , which was strongly sensitive to atmosphere. This effect was increased in oxidizing atmosphere mainly because of an increase in potential barrier hei ght whereas decreased in reducing atmosphere mainly because of a decrease i n potential barrier height. (C) 2001 Elsevier Science B.V. All rights reser ved.