Large acoustic thermal hysteresis in relaxor ferroelectric Pb(Zn1/3Nb2/3)O3-PbTiO3

The diffuse phase transition in relaxor-based 0.93Pb(Zn1/3Nb2/3)O3–0.07PbTiO3 ferroelectric single crystals is studied by observing the large thermal hysteresis over 100 K of the longitudinal acoustic (LA) phonon. By observing this hysteresis in the LA phonon frequency with different temperature-cycles, it is concluded that nonequilibrium states are induced by supercooling. Relaxor ferroelectrics easily go supercooling, because they demonstrate structural hierarchy like glass-forming materials. The inhomogeneous structure disrupts sharp phase transitions, revealing diffuse phase transition on cooling. However, annealing at low temperatures reduces the inhomogeneity markedly. These interpretations are consistent with LA phonon behavior under electric fields, which reduce the inhomogeneity.