Characterization of manganese-doped BaTi O₃ - (Bi_1/2 Na_1/2) Ti O₃ positive temperature coefficient of resistivity ceramics using impedance spectroscopy

Small amount of manganese (Mn)-doped BaTi O3 - (Bi12 Na12) Ti O3 (BT-BNT) positive temperature coefficient of resistivity ceramics are investigated by impedance analyses. The impedance/modulus spectroscopic plots reveal that a third resistance-capacitance (RC) response besides grains and grain boundaries is exhibited in the Mn-free BT-BNT ceramic with 4 mol % BNT, but is not observed in the Mn-doped samples. The third RC element can be attributed to a barium vacancy-rich layer in the outer grain region. The evidence of impedance spectroscopy indicates that the highly Bi donor is partially compensated by the Mn acceptor and the predominant charge compensation defect shifts from barium vacancies to electrons with doping small amount of Mn dopant.