Ag1-xNaxNbO3(ANN) solid solutions: from disordered antiferroelectric AgNbO3to normal antiferroelectric NaNbO3

The ceramics of new solid solutions of Ag 1- x Na x NbO 3 (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 ( T ) maxima, associated with M 1 -M 2 and M 2 -M 3 phase transitions. The evolution from disordered antiferroelectric AgNbO 3 to normal antiferroelectric NaNbO 3 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.