Preparation and properties of PTCR ceramics with low resistivity sintered at low temperature

Two types of positive temperature coefficient of resistance (PTCR) ceramics with relatively low room-temperature resistivity were prepared using the four-component system (Ba, Sr, Ca, Pb)TiO3 with lanthanum oxide (La2O3) as the donor dopant and boron nitride (BN) as the sintering aid. The first type of materials was sintered at 1080 degreesC for 2 h. It has a Curie point T(c)similar to 120 C-degrees, a room-temperature resistivity rho(v) of 58 Omega cm and a resistivity jump Deltarho of 3 x 10(4) Omega cm around T-c. For the second type of materials that were sintered at 1100 degreesC for 20 min, T(c)similar to 120 C-degrees, rho(v) = 19 Omega cm and Deltarho = 10(4) Omegacm. These PTCR ceramics are considered to be suitable materials for fabricating multilayer PTCR devices by the co-firing process. Factors associated with the composition that influence the PTCR property of the materials are discussed. (C) 2002 Kluwer Academic Publishers.