New lead-free non-stoichiometric perovskite relaxor ceramics derived from BaTiO_3

摘要

The present work concerns the preparation and dielectric characterization of some new non-stoichiometric lead-free ceramics with perovskite compositions derived from BaTiO_3. 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 BaTiO_3-Ba_(0.5)NbO_3 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-TiO_2-Nb_2O_5. The variation in the Curie temperature T_C or the temperature T_m of the maximum of ε'_r decreased when the composition deviated from BaTiO_3 and when the number of vacancies increased. On the contrary, the relaxor state was favored by such a deviation.