Effect of the Reoxidation on Positive Temperature Coefficient Behavior of BaTiO3–Bi0.5Na0.5TiO3

As a positive temperature coefficient of resistivity (PTCR) material, (1− x )BaTiO 3 – x (Bi 0.5 Na 0.5 )TiO 3 (BT–BNT, 0.01≤ x ≤0.08) ceramics without any donor doping were prepared by a conventional solid‐state reaction method. All samples were sintered in an N 2 atmosphere at 1340°C, followed by reoxidizing at 800°–1100°C in air. The PTCR characteristics of BT–BNT ceramics were investigated in terms of BNT content, reoxidation temperature, and time. Room‐temperature resistivity (ρ RT ) of simples sintered in N 2 decreased to 10 2 Ω·cm, and the jump in resistivity (maximum resistivity [ρ max ]/minimum resistivity [ρ min ]) was enhanced by three orders of magnitude through a suitable reoxidation process without sacrificing the ρ RT . The Curie temperature ( T c ) 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 ρ RT of 2 × 10 2 Ω·cm, a typical PTC effect of ρ max /ρ min >10 3 , and a T c of 160°C.