New lead-free non-stoichiometric perovskite relaxor ceramics derived from BaTiO3

The present work concerns the preparation and dielectric characterization of some new non-stoichiometric lead-free ceramics with perovskite compositions derived from BaTiO3. Lead-free compositions could be of great interest for environment-friendly applications (dielectric for capacitors, actuators, etc.). These materials have been shown to be either classical or relaxor ferroelectrics. In the first part of this article, the BaTiO3-Ba0.5NbO3 system concerns the cationic non-stoichiometry occurring only in the 12-coordination crystallographic site. In the second part, the influence of non-stoichiometry also occurring in the anionic site was determined in compositions belonging to the ternary system 2BaO-TiO2-Nb2O5. The variation in the Curie temperature T-C or the temperature T-m of the maximum of e;. decreased when the composition deviated from BaTiO3 and when the number of vacancies increased. On the contrary, the relaxor state was favored by such a deviation. (C) 2003 Elsevier SAS. All rights reserved.