Phase transformations in poled PZN-4.5%PT single crystal revealed by combined property measurements and high-resolution diffraction technique

The phase transformation of annealed and poled 0.955Pb (Zn _1/3Nb_2/3)O₃ -0.045 PbTiO₃ (PZN-4.5%PT) single crystals has been studied by means of combined bulk property measurements (dielectric permittivity and thermal current density measurements) and microstructural characterization (polarized light microscope and high-resolution x-ray diffraction). Our results showed that upon heating under zero-field condition, poled PZN-4.5%PT undergoes a R-(R+ R_NT +T+T_NT) - (T+T_NT) -C transformation sequence, where (R+R_NT) and (T+T_NT) denote that the rhombohedral and tetragonal phases present consist of a mixture of microscopic (R,T) and nanotwin (RNT, TNT) domains and C denotes the cubic phase. The R_NT and T _NT nanotwin domains were detected only in the temperature vicinity of the R-T transformation, possibly as a means to alleviate the transformation stress in the material. These nanotwin diffractions can be easily mistaken as monoclinic diffractions.