Dielectric and piezoelectric activities in (1-x)Pb(Mg _1/3Nb _2/3)O ₃-xPbTiO ₃ single crystals from 5 K to 300 K

Lead based relaxor single crystals have raised a considerable interest due to their outstanding piezoelectric properties. These piezoelectric properties are temperature dependent and are known to decrease when the temperature is decreased. The aim of this paper is to study the variation of the dielectric constant, the elastic compliance, the coupling factor, the piezoelectric charge coefficient, and the mechanical quality factor for rhombohedral single crystals of (1-x)Pb(Mg _1/3Nb _2/3)O ₃-xPbTiO ₃ (PMN-PT) poled along [001] in the 5 K-300 K temperature range. In particular, it has been shown that a relaxation phenomenon occurs around 100 K leading to a rapid decrease of the studied piezoelectric, mechanical, and dielectric constants just after a plateau. As a consequence, the similar behaviour of the dielectric constant, piezoelectric charge coefficient, and elastic compliance versus temperature leads to a temperature independent behaviour of the coupling factor above 100 K. This relaxation is also responsible for the minimum observed on the mechanical quality factor. By comparing the measured dielectric constant with the calculated one using the Landau-Ginsburg-Devonshire theory, this relaxation has been attributed to electrical charges freezing within the domain as the temperature is decreased.