Phase coexistence and Mn-doping effect in lead-free ferroelectric (Na1/2Bi1/2)TiO3 crystals

Phase transformations of (001)-cut (Na1/2Bi1/2)TiO3 (NBT) and 1 at. % Mn-doped NBT (Mn-NBT) crystals have been investigated by means of dielectric permittivity, conventional x-ray diffraction (XRD), and high-resolution synchrotron XRD and reciprocal space mapping. An R-R+T-T-C transition sequence was observed in NBT and Mn-NBT upon zero-field heating. R, T, and C are rhombohedral, tetragonal, and cubic phases, respectively. R+T represents that the ferroelastic T phase coexists with the ferroelectric R phase. The Mn dopant can enhance dielectric response and reduce the dielectric loss in the high-temperature region due to the increased degree of ordering.