Semiconducting ceramics produced using nanocrystalline barium titanate powder

Positive temperature coefficient of resistance ceramics of composition (Ba0.89Ca0.08Pb0.03)TiO3 + Y2O3 + MnO + SiO2 have been produced using barium titanate powder with an average crystallite size of 125 nm prepared by calcining barium titanyl oxalate at 900A degrees C. The effect of firing temperature on their microstructure and electrical properties has been studied. The results demonstrate that the ceramics possess semiconducting properties starting at a firing temperature of 1205-1215A degrees C. The room-temperature resistivity of the ceramics has a minimum at t (firing) a parts per thousand 1245-1250A degrees C. The samples sintered at 1250-1260A degrees C have the largest positive temperature coefficient of resistance. The highest electric strength (360 V/mm at rho(25A degrees C) = 290 Omega cm) is offered by the thermistor materials sintered at 1260A degrees C, which is 60-70A degrees C below the firing temperature of analogous ceramics produced by solid-state reaction.