Preparation and positive temperature coefficient of resistivity behavior of Ba0.95Ca0.05TiO3–BiYO3–Na0.5Bi0.5TiO3 ceramics

As a promising material for lead-free PTC thermistor ceramics, Nb2O5-doped (1 − x − y)Ba0.95Ca0.05TiO3–xNa0.5Bi0.5TiO3–yBiYO3 ceramics with complex perovskite structure were prepared by a conventional mix-oxide method and characterized with X-ray diffraction, scanning electron microscope and resistivity-temperature measurement instrument. The results showed that the tetragonality c/a of the perovskite lattice, the grain size, the Curie temperature and the room temperature resistivity of Ba0.95Ca0.05TiO3–Na0.5Bi0.5TiO3–BiYO3 ceramics varied with the increasing additions of BiYO3 and Na0.5Bi0.5TiO3. A further study was conducted by impedance spectroscopy so as to study the effects of Na0.5Bi0.5TiO3 and BiYO3 on the resistivity of grains and grain boundaries.