Joint Research on the Fundamental Functions of Relaxors

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Crystal structure of ferroelectric relaxor Pb (Mg_<1/3>Nb_<2/3>)O_3 from room temperature down to 10K was determined by the neutron diffraction technique with the Rietveld analysis. It was found that the crystal structure at room temperature is a disordered perovskite where a Pb atom is distributed spherically around the ideal A site in the perovskite, an O distributes in rings near {100} surfaces, while a Mg/Nb is located at the B site. When temperature is lowered, the polar rhombohedral region with atomic shifts along the {111} direction develops in the disordered cubic matrix. The second harmonic generation was also measured using a ceramic sample under the field-heating after zero field-cooling process. The non-ergodic behavior was observed.