Morphotropic domain structures and phase transitions in relaxor-based piezo-/ferroelectric (1-x)Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) single crystals

The domain structures and phase transitions of relaxor-based piezo-/ferroel ectric (1-x)Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) [PMNT] single crystals, grown from high temperature solutions, have been analyzed by polarized light microscop y using an optical crystallographic approach. The substitution of Ti4+ ions for the B-site complex (Mg1/3Nb2/3)(4+) ions in the relaxor PMN results in a long-range symmetry breaking, as revealed by the formation of birefringe nt macrodomains. The domain structures of the PMNT80/20 crystals indicate a primitive trigonal symmetry at room temperature with a weak birefringence. PMNT crystals with 50% Ti show tetragonal domain structures, reflecting th e symmetry of PbTiO3. Single crystals of PMNT65/35 exhibit complex morphotr opic domain structures, which are composed of both the trigonal and the tet ragonal phase intimately mixed together. The domain structures, the sequenc e and temperature of phase transitions have been interpreted in relation to the morphotropic phase boundary behavior of the PMN-PT system. It is shown that in situ analysis of domain structures and phase transitions can be us ed as a nondestructive analytical tool for evaluating the local morphotropi c composition and the properties, which sensitively depend upon the individ ual domains and the Ti4+ concentration. The analysis of morphotropic domain structures and phase transitions provides a better understanding of the mi croscopic mechanisms of the enhanced piezoelectric properties recently disc losed in PMNT and other relaxor-based piezocrystals. (C) 2000 American Inst itute of Physics. [S0021-8979(00)01805-3].