ANALYSIS OF DIELECTRIC PARAMETERS AND ION HOPPING RATES IN THE BETA-LNNB3O9 PHASES (LN = LA, CE, PR AND ND)

The electric transport characteristics of beta-LnNb3O9 (Ln=La, Ce, Pr and Nd) orthorhombic phases, measured by ac impedance spectroscopy, were recently reported. In this work, a detailed analysis of dc component, obtained directly from ac data, is given. The dc conductivity of beta-CeNb3O9 is quite close to the bulk conductivity at low temperatures. Different behaviour is shown in the other three cases. The hopping rate characteristics of the charge carriers and an estimation of the relative carrier concentration are also presented. Exhaustive analysis has been made on admittance versus frequency plots to extract hopping rate and dc values. The beta-LnNb3O9 compounds show Arrhenius behaviour in their hopping rate and dc characteristics. Finally, the behavior with temperature and frequency of dielectric parameters like tan delta and permittivity are discussed.