Room Temperature Ferroelectricity in Na<sub>1−<i>x</i></sub>Sr<sub><i>x</i>/2</sub>◻<sub><i>x</i>/2</sub>NbO<sub>3</sub> through the Introduction of Cationic Vacancies

The present study relates structural and microstructural modifications in the Na<sub>1−<i>x</i></sub>Sr<sub><i>x</i>/2</sub>◻<sub><i>x</i>/2</sub>NbO<sub>3</sub> solid solution with variations in the dielectric behavior when changing the chemical composition as an unprecedented investigation in lead-free ferroelectric compounds. X-ray diffraction, electron diffraction, and high resolution electron microscopy have been used as techniques to obtain a complete knowledge of the structural and microstructural evolution of the system as a result of the doping process. In this paper, we focus our attention in the relevant structural transition which occurs in the 0 < <i>x</i> ≤ 0.2 composition range correlated to the change in dielectric behavior observed from the electric characterization performed. The microstructural study performed in this system in correspondence with the exhaustive electric characterization provides evidence about the evolution suffered by the system in which the changeable A-vacancy concentration might play a crucial role by tuning the electric behavior.