Effect of the Nb2O5 content on electrical properties of lead-free BaTiO3–Bi0.5Na0.5TiO3 ceramics

(1−x)BaTiO3–xBi0.5Na0.5TiO3 (BT–BNT) ceramics were prepared by the solid-state reaction method. With an increase of BNT content, both the Curie temperature and the room temperature resistivity increased. At 1 mol% BNT addition, the sample was not semiconducting, due to Bi2O3 volatilization resulting from the decomposition of pre-calcined BNT during sintering. Appropriate extra Nb2O5 doping in the raw materials could offset Bi2O3 volatilization and neutralize the redundant acceptor Na+ ions. When the extra Nb2O5 content was 0.6 mg, the sample room-temperature resistivity was 6.3×103 Ω cm, with the Curie point about 135 °C and a high PTC effect of ∼3 orders of magnitude.