The electrical properties of LiNbO3 ceramic pellets were investigated by impedance spectroscopy in the temperature range of 450–800 °C. Impedance data are presented in the Nyquist plot which, in addition to the separation of grain and grain boundary contributions, allows the determination of the relaxation frequency of samples. The results of bulk electrical conductivity and its activation energy, confirmed by measuring samples with different geometrical parameters, are presented. Relaxation frequencies follow an Arrhenius behavior with the same activation energy found for the electrical conductivity. Relaxation frequencies were also used to calculate bulk dielectric constants and the results are compared to the behavior of the real part of the sample dielectric constant.
The electric permittivity of the sodium niobate ceramic was investigated in the temperature range from 15 up to 900 K, at frequencies from 100 Hz to 1 MHz. Three anomalies were found in the permittivity curve. A phase transition for NaNbO3 was assigned to anomaly at around 280 K, while other two ones have previously been reported. In addition, the dielectric permittivity dependence with the temperature and frequency, at temperatures lower than 400 K, showed two regions with typical characteristics of a relaxor ferroelectric materials.
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