Optical and Structural Studies of Long-Range Order Development in Relaxor Ferroelectrics

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Abstract
Development of long-range order in relaxor ferroelectrics [Pb(Mg 1/3 Nb 2/3 )O 3 ] 1- x -[PbTiO 3 ] x (PMN/ x PT) and Pb(Zn 1/3 Nb 2/3 )O 3 (PZN) has been investigated by neutron powder diffraction and birefringence along with transmission-electron and optical microscopies. The Rietveld analysis of PZN revealed that the rhombohedral phase develops gradually in the cubic matrix but that it does not prevail on the whole crystal even at low temperature. Development of the heterophase is quite similar to that observed in PMN/ x PT with x =0. Temperature dependence of the birefringence induced by an electric field was also measured using the PMN/ x PT with x =0 and 0.1, and was found to depend strongly on pre-history of the specimen; zero-field cooling, field-heating, field-cooling and zero-field heating exhibit differences in the temperature dependence. The development of long-range order was observed under the electric field. The birefringence increases quite slowly at the first stage with a incubation time. After the long incubation, the increase becomes significant and eventually is saturated. A possible origin of these phenomena was discussed.