Ceramics-Silikáty 49, (3) 188 - 194 (2005)

The effects of the grain boundary modifiers H₃BO₃ and SiO₂ before and after the calcination steps on the microstructure and on the positive temperature coefficient of resistivity (PTCR) of Sb₂O₃ donor-doped Ti-excess barium titanate (BT) were investigated. The additions before calcination resulted in coarse porosity between the grains and the additions after calcination gave rounded, uniform grains with a pronounced decrease in porosity. The Sb₂O₃ donor-doped BT became conductive when sintered at 1300°C giving a room temperature resistivity (ρ_RT) of 400 Ohm cm. The ρ_RT values of the B₂O₃ and SiO₂ contained samples decreased when modifiers were added after the calcination step. The Sb₂O₃ donor-doped BT showed a PTCR effect of 4.2 orders of magnitude and a range of 4.5-5.0 orders of magnitude were obtained for the B₂O₃ and SiO₂ added samples.