Freezing of the Nb5 + ion dynamics in AgNbO3 studied by linear and nonlinear dielectric response

Abstract

Linear and nonlinear dielectric measurements ofAgNbO3 ceramics and single crystals were carried out for the M phases (77–673 K). The linear dielectricresponse is dominated by the contribution of the submillimetre relaxational mode related to theNb5 + ion dynamics(M2–M3). On the other hand,nonlinear dielectric χ3′ susceptibility revealed anomalies at three characteristic temperatures:90, 325 and 448 K. Two later ones are connected with changes of theNb5 + ion dynamics.At Tf = 448 K a partialfreezing of the Nb5 + ion displacement to the anti-polar, antiferroelectric array takes place. At 325 K furtherfreezing of Nb and Ag displacements to the polar weak relaxor ferroelectric or dipolar glasstransition occurs. This polar state coexists with the ground antiferroelectric one.