Anomalous resistivity of sodium-lithium-niobium-tantalum ceramics

The electric resistance R of the samples of a Na0.88Li0.12Nb0.5Ta0.5O3 ferr oelectric ceramic composition with the electron conductivity increased by t hermal reduction in vacuum exhibit anomalous temperature variation of the p osistor type in the temperature region of 350-400 degrees C, where the nonr educed samples exhibit transition to the state with superionic conductivity . The R(T) anomaly was observed during the electrical measurements both in air and in vacuum. The effect depends on the degree of material reduction a nd the measurement frequency, reaching 4-5 orders of magnitude for the de m easurements in samples with maximum conductivity. It is suggested that the R(T) anomaly is localized in the near-electrode layer and is related to a m utual influence of the electron and ion transport processes. (C) 2000 MAIK "Nauka/Interperiodica".