Negative Capacitance Effect in the Low-Frequency Impedance of Barium Strontium Titanate Semiconductor Ceramics

Abstract

Polycrystalline (Ba_0.85Sr_0.15)_0.999Ce_0.001TiO₃ samples prepared by a standard ceramic processing technique for positive temperature coefficient of resistance materials have been characterized by impedance spectroscopy. Major attention has been paid to the inductive character of the impedance in the low-frequency range of the measuring signal. In the literature, such an impedance is interpreted in terms of a negative capacitance effect. Based on analysis of the existing notions of the structure of grain boundaries in ceramics, we have proposed an equivalent circuit that models frequency dependences of the immitance in good agreement with experimental data.