METASTABLE STATE WITH HIGH ELECTRIC CONDUCTIVITY IN Li0,12Na0,88Та0,25Nb0,75O3 SYNTHESIZED AT HIGH PRESSURE

Abstract

The results are presented of a study of a ferroelectric solid solution Li0,12Na0,88Та0,25Nb0,75O3 with a perovskite structure based on sodium niobate and synthesized under high pressure and temperature. In the temperature range of 290-800 K, the values of the specific conductivity at direct current, the activation energy of charge carriers, and the real part of the dielectric constant were determined by the method of impedance spectroscopy. Evolution of temperature anomalies of specific conductivity and dielectric constant during thermal cycling is shown. The observed effects are associated with structural phase transitions, and the Curie temperature is determined. The Li0,12Na0,88Та0,25Nb0,75O3 undergoes a second-order phase transition. It was found that a metastable phase is formed in Li0,12Na0,88Та0,25Nb0,75O3, which has a high electrical conductivity at the room temperature. When heated above the Curie temperature, this phase is destroyed. Possible mechanisms of the discovered phenomena are discussed.

Keywords

• impedance spectroscopy
• solid solutions based on sodium niobate
• high pressure
• metastable phase
• phase transitions