Effect of the Reoxidation on Positive Temperature Coefficient Behavior of BaTiO3–Bi0.5Na0.5TiO3
As a positive temperature coefficient of resistivity (PTCR) material, (1[minus]x)BaTiO3[ndash]x(Bi0.5Na0.5)TiO3 (BT[ndash]BNT, 0.01[le]x[le]0.08) ceramics without any donor doping were prepared by a conventional solid-state reaction method. All samples were sintered in an N2 atmosphere at 1340°C, followed by reoxidizing at 800°[ndash]1100°C in air. The PTCR characteristics of BT[ndash]BNT ceramics were investigated in terms of BNT content, reoxidation temperature, and time. Room-temperature resistivity ([rho]RT) of simples sintered in N2 decreased to 102[Omega]·cm, and the jump in resistivity (maximum resistivity [[rho]max]/minimum resistivity [[rho]min]) was enhanced by three orders of magnitude through a suitable reoxidation process without sacrificing the [rho]RT. The Curie temperature (Tc) was shifted to a high temperature (>130°C) with an increase in the BNT content. With the addition of 4 mol% BNT, the obtained ceramic exhibited a low [rho]RT of 2 × 102[Omega]·cm, a typical PTC effect of [rho]max/[rho]min>103, and a Tc of 160°C.
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