Ag1-xNaxNbO3 (ANN) solid solutions:: from disordered antiferroelectric AgNbO3 to normal antiferroelectric NaNbO3

The ceramics of new solid solutions of Ag1-xNaxNbO3 (ANN) have been sintered for the whole concentration range. Low frequency dielectric investigations (120-800 K) and DTA investigations (290-600 K) revealed a series of phase transitions. Two predominant aspects of the Na substitution have been found. The first one is related to a large increase of thermal hysteresis of the M-3-O-1 phase transition which points to its martensitic nature. The second one is related to the gradual disappearance of two diffuse epsilon(T) maxima, associated with M-1-M-2 and M-2-M-3 phase transitions. The evolution from disordered antiferroelectric AgNbO3 to normal antiferroelectric NaNbO3 is considered. The influence of the oxygen octahedron size on the Nb ion dynamics is discussed. From the results obtained a phase diagram of the ANN system has been proposed.