Abstract

As a pore precursor, carbon black with different content of 0 to 60 vol% were added to (Ba,Sr)TiO_3 powder. Porous (Ba,Sr)TiO_3 ceramics were prepared by pressureless sintering at 1350°C for 1h under air. Effects of carbon black content on the microstructure and PTCR characteristics of porous (Ba,Sr)TiO_3 ceramics were investigated. The porosity of porous (Ba,Sr)TiO_3 ceramics increased from 6.97% to 18.22% and the grain size slightly decreased from 7.51;µm to 5.96;µm with increasing carbon black contents. PTCR jump of the (Ba,Sr)TiO_3 ceramics prepared by adding carbon black was more than 105, and slightly increased with increasing carbon black. The PTCR jump in the (Ba,Sr)TiO_3 ceramics prepared by adding 40 vol% carbon black showed an excellent value of 9.68times105, which was above two times higher than that in (Ba,Sr)TiO_3 ceramics. These results correspond with Heywang model for the explanation of PTCR effect in (Ba,Sr)TiO_3 ceramics. It was considered that carbon black is an effective additive for preparing porous BaTiO_3 based ceramics. It is believed that newly prepared (Ba,Sr)TiO_3 cermics can be used for PTC thermistor.

• Keywords: Carbon black;Porous (Ba,Sr)TiO_3 ceramics;PTCR;Porosity;Grain size;