Electrical properties of Nb-doped and Nb-Mn-codoped BaTiO_3-(Bi_(0.5)Na_(0.5))TiO_3 lead-free PTCR ceramics

摘要

Nb-doped and Nb-Mn-codoped (l-xmol%)BaTiO_3-xmol%(Bi_(0.5)Na_(0.5))TiO_3 (BBNTx) lead-free positive temperature coefficient of resistivity (PTCR) ceramics were prepared by the conventional solid state reaction method. The XRD patterns indicated that all BBNTx samples formed a single perovskite structure with tetragonal phase. 0.25 mol% Nb doped BBNT1 ceramic, sintered at 1330°C for 1h in air, had low room-temperature resistivity (ρ_(25)) of 80 Ω·cm and a high resistivity jump (maximum resistivity [ρ_(max)]/minimum resistivity [pmin]) of 4.2 orders of magnitude with T_c about 152°C. The Nb-doped BBNTx (10≤x≤60) ceramics also showed distinct PTC effect with T_c between 185 and 232°C by sintering in N_2, which was shut off when samples were cooled to a low temperature. In addition, The Nb-Mn-codoped BBNT1 ceramics exhibited higher resistivity jump than the single Nb-doped ones, with increasing the room-temperature resistivity.