Anomalous phase in the relaxor ferroelectric Pb(Zn1/3Nb2/3)O-3

X-ray diffraction studies on a Pb(Zn1/3Nb2/3)O-3 (PZN) single-crystal sample show the presence of two different structures. An outer layer exists in the outer most similar to10 to 50 mum of the crystal, and undergoes a structural phase transition at the Curie temperature T(C)approximate to410 K. The inside phase is, however, very different. The lattice inside the crystal maintains a cubic unit cell, while ferroelectric polarization develops below T-C. The lattice parameter of the cubic unit cell remains virtually a constant, i.e., much less variations compared to that of a typical relaxor ferroelectric, in a wide temperature range of 15 to 750 K. On the other hand, broadening of Bragg peaks and change of Bragg profile line shapes in both longitudinal and transverse directions at T-C clearly indicate a structural phase transition occurring.