Anomalous behaviour of dynamic electrical conductivity in semiconductor ferroelectric ceramics near the phase transition temperature

Abstract

The article presents the results of a study of the electrical properties of semiconductor perovskite ceramics based on a solid solution of barium-strontium titanate with the addition of the rare earth element of cerium with the initial formula Ba1–x–y SrxCeyTiO3 (x = 0.05, y = 0.003). A scanning electron microscope was used to obtain images of the sample surfaces and the elemental composition data. The measurements were performed by impedance spectroscopy in the temperature range of 348-385 K in the frequency range of 102–106 Hz using an LCR metre. It was found that there is an anomalous behaviour in the dynamic electrical conductivity of the samples in the temperature range close to the ferroelectricparaelectric phase transition. This is expressed by a decrease in the value of the real part of the dynamic conductivity with an increase in frequency. An analysis of the simplified equivalent circuit of the intergranular barrier showed that this anomaly can be explained by introducing an inductive element into the circuit. This element can be considered a “negative capacitance element”. Following the results of the study, a conclusion was made about the generalised character of the phenomenon

Keywords

• semiconductor ceramics
• impedance spectroscopy
• negative capacitance effect
• posistor