Crystal symmetry transition and its influence on optical, dielectric, and ferroelectric properties in (1-x)Na0.5Bi0.5TiO3-xSrTiO3 system.

Ferroelectric perovskites materials are the most promising materials because of their multifunctional applications as well as the ongoing fundamental research on them. The present study investigates the correlation between the crystal structure and various physical properties such as dielectric, ferroelectric, and optical properties of Sr2+ modified Sodium bismuth titanate Na 0.5 Bi 0.5−x Sr x TiO 3 (x = 0.00, 0.02, 0.04, and 0.06) synthesized by solid-state reaction method. Rietveld refinement of the X-ray diffraction pattern reveals that the system undergoes a crystal symmetry transition from a two-phase crystal symmetries system (rhombohedral (R3c) and tetragonal (P4bm)) to a three-phase crystal symmetries system (rhombohedral (R3c), tetragonal (P4bm) and Cubic (Pm 3 ̅ m)) with the rise in Sr2+ concentration in Na 0.5 Bi 0.5−x Sr x TiO 3 which is the foremost reason behind the variation of physical properties of the system. The dielectric constant and maximum polarization increase with the Sr2+ concentration up to 2% and it decreases with the further increase in Sr concentration due to the distortion in crystal structure induced by the introduction of cubic phase (Paraelectric) in the system. The maximum value of the dielectric constant is estimated to be 3629 at a low frequency on the Na 0.50 Bi 0.48 Sr 0.02 TiO 3 system. The optical band gap (E g) of Na 0.5 Bi 0.5−x Sr x TiO 3 (x = 0.00, 0.02, 0.04, and 0.06) ceramics are found to vary between 3.202 eV to 3.172 eV which indicates the semiconducting nature of prepared samples but urbach energy shows an opposite behaviour i.e. increases with Sr concentration. [Display omitted] • Crystal symmetry transition occurs from R3c + P4bm to R3c + P4bm + Pm 3 ̅ m. • Na 0.50 Bi 0.48 Sr 0.02 TiO 3 exhibits Maximum polarization of 7.05 μC/cm2. • The highest dielectric constant is found to be 3629 for Na 0.50 Bi 0.48 Sr 0.02 TiO 3. • Na 0.50 Bi 0.48 Sr 0.02 TiO 3 ceramics exhibits a low optical band gap of 3.138 eV. • Sr2+ modified NBT can be utilized in various technological applications. [ABSTRACT FROM AUTHOR]