Electric field dependent phase stability and structurally bridging orthorhombic phase in Na0.5Bi0.5TiO3-x%BaTiO3 crystals near the MPB

The dielectric, domain and structural properties of Na0.5Bi0.5TiO3-5.2%BaTiO3 (NBT-5.2%BT) single crystals were studied as a function of temperature in unpoled and 〈001〉〈001〉-poled conditions. A rhombohedral phase was found to coexist with a small volume fraction of a tetragonal one in the unpoled condition. However, in the poled condition, a single cc-domain tetragonal state was found to be stable at room temperature with a piezoelectric d33d33 constant of 400 pC/N. On heating above 105 °C, this single cc-domain tetragonal state first transformed into an intermediate orthorhombic structure at 130 °C, and then subsequently into a rhombohedral one above 140 °C.

Research highlights
► A tetragonal phase was found for 〈001〉〈001〉-poled NBT-5.2%BT single crystals.
► The tetragonal phase was stable below 130 °C.
► On heating from the poled condition, an orthorhombic phase was found at 130 °C.
► Above 140 °C, a rhombohedral phase was found to be stable.