Abstract
Lanthanum (La) doped BaTiO3-(Bi0.5Na0.5)TiO3 (BT-BNT) positive temperature coefficient of resistivity (PTCR) ceramics were prepared by a conventional solid state reaction method. The microstructure and PTCR effect of BT-BNT ceramics were investigated by scanning electron microscopy and measurement of resistivity-temperature dependence. The BT-BNT ceramics sintered in a N2 gas flow possessed low room-temperature resistivity (ρRT < 102 Ω·cm) and PTCR effect wasn't remarkable (ρmax/ρmin < 10); through a proper reoxidation process, the ceramics showed a typical PTCR effect (ρmax/ρmin > 103) but with a high room-temperature resistivity (ρRT > 103 Ω·cm). Room-temperature resistivity increased with the raising content of BNT. The Curie temperature (Tc) of BT-BNT ceramics shifted to 160°C for the 8mol% BNT added. With the addition of 4mol% BNT, the obtained BT-BNT ceramics reoxidized at 950°C possessed ρRT = 103 Ω·cm and exhibited a resistivity jump (ρmax/ρmin > 103) at 150°C. The possible mechanism underlying the PTCR behavior in BT-BNT ceramics was discussed.
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