Induction of Relaxor Behavior in Na1−xSrx/2◻x/2NbO3 through the Introduction of Cationic Vacancies

Materials in the Na 1− x Sr x /2 ◻ x /2 NbO 3 system (0.3 ≤ x ≤0.4) have been investigated by combining diffraction methods and high resolution electron microscopy with dielectric measurements. They undergo a microstructural evolution by continuously decreasing the coherent structural domain size as a consequence of the random distribution of the growing A-vacancy concentration. Change in the electrical properties occurs from the achievement of relaxor ferroelectric character in Na 0.7 Sr 0.15 NbO 3 to the strongly diffuse phase transition of Na 0.6 Sr 0.2 NbO 3 . The nanometric size of the structural domains found in the relaxor material led us to discuss the relationship between structural domain and polar region.