Processing characteristics of PTCR ceramics with low sintering temperature

The processing behavior of PTCR ceramics of (Ba,Sr,Ca,Pb)TiO^sub 3^ solid solution composition with additives of lanthanum oxide (La^sub 2^O^sub 3^) and boron nitride (BN) was studied. The ceramics can be sintered at temperatures as low as 1100 °C and possess rather low room-temperature resistivity with good PTCR effect. The sample ball milled with de-ionized water exhibits a more uniform microstructure compared to the sample ball-milled with alcohol. Particle size of less than 1 μm was found to be adequate for preparing the ceramics and the finer particles (≤0.45 μm) do not significantly improve the PTCR behavior. The performance of the PTCR sample is not sensitive to the sintering parameters such as the sintering time and cooling rate. This may be ascribed to the presence of excess BaO in the sample and the low sintering temperature, thereby eliminating the effect of Ba ion vacancies on the properties of the PTCR sample.[PUBLICATION ABSTRACT]