Pyroelectric Study on Dipolar Alignment in 0.69Pb(Mg_1/3Nb_2/3)O₃−0.31PbTiO₃ Single Crystals

Pyroelectric measurements are conducted during zero-field heating in 001, 110 and 111 poled 0.69Pb(Mg_1/3 Nb_2/3)O₃−0.31PbTiO₃ single crystals. Compared to the room−temperature-poled samples, the crystals poled by using the field cooling method show broad but well recognizable pyroelectric current peaks near 190°C, which is much higher than the Curie point (126°C) of the crystal. We propose that this peak of the crystals poled by field-cooling above the Curie point is ascribed to the order-disorder transition of the dipoles in polar nano-regions formed at the Burns temperature.