Effect of segregation on Mn-doped relaxor-PT single crystal

The effect of compositional segregation on the properties of relaxor ferroelectric single crystal are attracting increasing attention for its serious limitation on the application field. In this paper, the composition, phase structure, optical properties and electric properties of Mn-doped Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT) single crystal were investigated. The real composition of the single crystal fluctuated around the original ratio, except for MnO₂. The single crystal contained less Mn element after removing inclusions compared with the starting ratio. The single crystal samples exhibited rhombohedral phase (R phase), orthorhombic phase (O phase) and tetragonal phase (T phase) structures with different composition due to the segregation. The rhombohedral to tetragonal phase transition temperature (T_R-T) shifted to a lower value along the growth direction, while the Curie Temperature (T_C) shifted to a higher value instead. The relaxation level of the single crystal went down to a lower level when the crystal structure changed from R phase to T and O phase. The coercive field (E_C) with [001] poling in R phase remained stable before a rise in O phase and T phase. However, the composition segregation didn't obviously affected the internal bias field and kept around 0.2 kV/cm. The piezoelectric coefficient d₃₃ and unipolar strain with poling direction along [001] had the same trend along growth direction. The curves of them both took a rapid fall at the top of the single crystal boule, which related to the T phase.