Cryogenic dielectric and piezoelectric activities in rhombohedral (1 - X)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃single crystals with different crystallographic orientations

We report the cryogenic dielectric and piezoelectric activities in [0 0 1]-, [1 1 0]- and [1 1 1]-oriented rhombohedral (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3single crystals for temperatures down to -200 °C. Unusual dielectric relaxation resulting from collective pinning of randomly distributed point defects to ferroelectric macrodomain walls is observed instead of a phase transition in all the poled crystals below -150 °C rather than in the unpoled ones. Stiffening of the poled crystals by the cryogenic temperature-induced pinning effect leads to a characteristic decrease in the piezoelectric coefficient (d31) and the compliance coefficient ( ), along with a similar quantitative increase in frequency constant (N31). An almost temperature-independent property region is revealed in a wide temperature range of -50 to -150 °C, enabling applications of the crystals in cryogenic fields.