BaTiO_3-(Bi_(1/2)Na_(1/2))TiO_3 solid-solution semiconducting ceramics with T_c > 130℃

摘要

As a candidate of a lead-free positive temperature coefficient of resistivity (PTCR) material, barium titanate (BaTiO_3)-based solid-solution ceramics, Ba_(1-x)(Bi_(1/2)Na_(1/2))_xTiO_3 with x=0.05 (BBNT5), have been synthesized by an ordinary sintering technique. Temperature dependences of the dielectric and ferroelectric properties show ferroelectric and paraelectric phase transition of the ceramics with the Curie temperature of T_c=170℃, which is higher than that of BaTiO_3 (130℃). The La-doped BBNT5 ceramics display low p values of 10~2-10~3 Ω cm at room temperature and their abrupt changes of 10~2-10~4 at about 220℃. The reduced BBNT5 ceramics show small PTCR characteristics compared to the La-doped ones.