Dielectric Relaxation in Ba 2NaNb 5(1- x)Ta 5 xO 15 Single Crystrals

This paper presents the results of dielectric dispersion in Ba 2 NaNb 5(1- x ) Ta 5 x O 15 (BNNT) single crystals over the frequency range 1 kHz to 4 GHz. The fundamental dielectric dispersion occurs above 10 7 Hz and is caused by a soft relaxational mode. This mode gives the main contribution to the high static permittivity which fits the Curie-Weiss law. The results indicate the anharmonic motion of the Nb(Ta) atoms and the order-disorder nature of the proper ferroelectric phase transition in BNNT.