Low-frequency dielectric dispersion in NaNbO3 single crystals

Dielectric measurements have been performed in NaNbO3 single crystals in the frequency range 20 Hz - 1MHz and temperature range 320 K-750 K. A low-frequency relaxation process is observed in the temperature range above phase transition point Te and in vicinity of Tc. The obtained data were fitted to Cole-Cole formula. The mean relaxation time obeys the Arrhenius law above T-C. The dispersion step ae (the maximum value of Delta epsilon approximate to 2000) is temperature dependent. Both relaxation parameters: tau and Delta epsilon as have high discontinuity at Tc. The occurrence of a low-frequency relaxation in NaNbO3 may be connected with the disorder of crystal structure already at high temperatures. This disorder can lead to arising of local dipoles (polar regions).