Potential Barrier Behavior of BaTiO₃–(Bi_0.5Na_0.5)TiO₃ Positive Temperature Coefficient of Resistivity Ceramic

High-Curie-temperature (T_c) lead-free Y-doped 90 mol%BaTiO₃–10 mol%(Bi_0.5Na_0.5)TiO₃ ceramic with positive temperature coefficient of resistivity (PTCR) is prepared by the conventional solid state reaction in nitrogen atmosphere. The PTCR ceramic exhibits a room-temperature resistivity (ρ₂₅) of ～500 Ω?cm and a high PTCR effect (maximum resistivity (ρ_max)/minimum resistivity (ρ_min)) of ～4.5 orders of magnitude. A capacitance-voltage approach is first employed to calculate the potential barrier (?) of the grain boundary of PTCR ceramic above T_c. It is found that the potential barrier changes from 0.17 to 0.77 eV as the temperature increases from 180 to 220°C, which is very close to the predictions of the Heywang–Jonker model, suggesting that the capacitance-voltage method is valid to estimate the potential barrier of PTCR thermistor ceramics.