Structural phase transition, optical and pyroelectric properties of lead-free single crystals

Abstract

0.14 at% Mn-doped 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3 (0.95NBT-0.05BT) lead-free single crystals were grown by a top-seeded solution growth method (TSSG). X-ray powder diffraction measurement showed that the as-grown single crystals exhibit rhombohedral perovskite structure with apparent distortion. With the increase of temperature, successive structural phase transitions occur in the Mn-doped 0.95NBT-0.05BT single crystals. After poling, apparent dielectric anomaly is induced accompanied by the increase of the character of diffuse phase transition and the decrease of the value of dielectric constant. The Mn-doped 0.95NBT-0.05BT single crystals exhibit complex domain structure, in which micro and macro domains coexist with statistically 4 mm symmetry. The Mn-doped 0.95NBT-0.05BT lead-free single crystals exhibit excellent piezoelectric and pyroelectric properties, which will lead to promising advance in piezoelectric and pyroelectric applications. The infrared-absorption band occurred around 630.6 cm−1 can be assigned to the “stretching” normal vibration of [Na1/2Bi1/2]/Ti-O group. The three diffused Raman bands centered around 300, 560 and 800 cm−1 can be attributed to F2g [TiO6] bending vibration, A1g [TiO6] stretching vibration and “soft mode” mixed by bending and stretching vibrations.