Interrelationship between Interphase Boundaries and Phase Contents near the Critical Compositions of Lead-Free Ferroelectric (Na_0.5Bi_0.5)TiO₃−BaTiO₃

Abstract

Heterophase structures in lead-free perovskite-type ferroelectric solid solutions of (1 − z)(Na_0.5Bi_0.5)TiO₃ − zBaTiO₃ are analysed for a few critical compositions near the morphotropic phase boundary (z = 0.05−0.07). Examples of the phase coexistence and elastic matching of the phases from different symmetry groups are considered to find optimum volume fractions of specific domain types and coexisting phases at the complete stress relief in two-phase samples. Some interrelations between these volume fractions are described using variants of the domain arrangement at changes in the composition and unit-cell parameters. The evaluated room-temperature volume fractions of the ferroelectric monoclinic (Cm symmetry) and tetragonal (P4mm symmetry) phases near the morphotropic phase boundary are in agreement with experimental data.

Keywords:

• Heterophase ferroelectric solid solution
• domain structure
• phase transition
• crystal structure
• volume fraction

Acknowledgments

The authors would like to thank Prof. Dr. A. E. Panich, Prof. Dr. I. A. Parinov, Prof. Dr. A. A. Nesterov, Dr. V. V. Eremkin, and Dr. V. G. Smotrakov (Southern Federal University, Rostov-on-Don, Russia), and Prof. Dr. D. Pandey (Banaras Hindu University, India) for their continuing interest in heterophase FE solid solutions. The research subject is concerned with the Programme Supporting the Research at the Southern Federal University Centre of Collective Use ‘High Technologies’, project RFMEFI59414X0002 (Russia).