Ferroelectric phase transition in relaxor ferroelectric single crystals 0.76PMN-0.24PT

The features of the single crystals 0.76PMN-0.24PT in dietectric, ferroetectric, pyroetectric properties and domain structures indicate that they are located between typical ferroetectrics and normal ones. The unpoled crystals present a transitional domain configuration between microdomains and typical macrodomains while the crystals on (001) cuts undergo fietd-induced phase transition under poling, showing two special temperature points T_d andT _m during the succedent heating procedure. The dietectric constant starts to decrease drastically at T_d during cooling, or the transformation from induced macrodomain to transitional domain takes place atT _d during heating. Ferroetectric-paraetectric phase transition or depolarization continues within the whole temperature range ofT _d-T _m, where ferroetectric phase in the form of transitional macrodomains coexists with paraetectric phase. Then the crystals macroscopically transoform into paraetectric phase containing ferroetectric microdomains at a temperature aboveT _m. However, owing to the influence of crystallite orientation on fietd-induced phase transition, the temperatureT _d does not appear in the same temperature-etectric fietd history in multicrystal ceramics with the same composition as the above single crystals.