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. (C) 2011 Elsevier B.V. All rights reserved.