Origin of dielectric anomaly in double perovskite Ba2CoNbO6

The dielectric properties of Ba2CoNbO6 were investigated in the frequency range of 100 Hz to 10 MHz and temperature range of 300–600 K. Two relaxations and a dielectric anomaly were observed. The low-temperature relaxation is a Maxwell–Wagner relaxation caused by the surface-layer effect; the high-temperature relaxation is attributed to the hopping of oxygen vacancies. The dielectric anomaly located at 485 K is an artificial effect caused by negative capacitance associated with the transition of carriers from localized to free states.