Electric-field poling effect on thermal stability of monoclinic phase in Pb(Mg1/3Nb2/3)0.74Ti0.26O3 single crystal

Phases and domains in a (1 1 0)-cut Pb(Mg1/3Nb2/3)0.74Ti0.26O3 (PMNT26%) single crystal have been investigated as functions of temperature and direct current (DC) electric (E) field by dielectric permittivity, polarizing microscopy, and electric polarization. The unpoled sample has a dominant rhombohedral (R) phase coexisting with monoclinic (M) phase domains, i.e. R/M at room temperature (RT). With 45 kV/cm DC poling applied along [1 1 0] at RT, a single domain of R phase with polar orientation perpendicular to the poling field, i.e. R, was obtained. No microcracking was observed under such high DC field poling. After the poling was removed, the poled sample has R/M microdomains, where the M distortion is close to the R phase. The zero-field-heating domain patterns in the unpoled and poled samples exhibit continuous polarization rotation via an intrinsic M phase in the regions of 355-373 and 365-378 K, respectively. Orthohombic (O) and tetragonal (T) phases were not observed in the temperature-dependent study. The whole crystal becomes cubic (C) phase near 393 and 399 K in the unpoled and poled sample, respectively. In brief, an R/M→M→C transition sequence takes place upon heating for both unpoled and poled samples.