Roles of Micro-cracking and Phase Transition on Electric Fatigue for 001-Oriented Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3 Single Crystals

摘要

In-situ observations of microstructure and polarization degradation under cyclic electric loadings are carried out for [001]-oriented Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3 ferroelectric single crystals. Direct evidences of the effects of micro-cracking and phase transition on the polarization degradation are revealed. Upon cyclic electric loading with a comparatively low field magnitude, there is no phase transition while the propagation of micro-cracks significantly reduces the polarization. When electric loading is cycled under a high field magnitude, the single crystal transforms from a rhombohedral phase to a monoclinic phase. Both micro-cracking and phase transition inhibit ferroelectric domain switching and reduces the number of electric dipoles that can efficiently switch their orientation under cyclic electric field. The phase transition degrades the polarization to a greater degree than do the micro-cracks. The findings are of importance concerning the long-term reliability of the high performance PMN-PT single crystals.