Piezoresponse force microscopic study of ferroelectric (1 - X)Pb(Sc _1/2Nb _1/2)O ₃ - xPbTiO ₃ and Pb(Sc _1/2Nb _1/2)O ₃ single crystals

The microscopic piezoelectric response and ferroelectric domain switching in the (001)-oriented rhombohedral piezo-/ferroelectric (1 - x)Pb(Sc _1/2Nb _1/2)O ₃ - xPbTiO ₃ (PSN-PT) and relaxor Pb(Sc _1/2Nb _1/2)O ₃ (PSN) single crystals were studied by piezoresponse force microscopy. PSN-PT shows clear domain structures while the domain contrast of PSN is very weak. For PSN-PT, after being fully poled vertically, its lateral domain structure is still composed of a multi-domain state. Both PSN-PT and PSN crystals respond to positive and negative DC field drives through piezoelectricity. However, their poling behaviors are different. For PSN-PT, during successive applications of a positive external electric field, the areas with piezoresponse in phase with the electric field grow at the expense of domains of opposite piezoresponse, implying a domain switching process via sideway motion of domain walls. On the other hand, in the PSN single crystal, the piezoresponse contrast of the alternatively poled area shows a uniformly fading and enhancing pattern, depending on the direction of the polarization component of the domains relative to the external field. While the domain pattern of PSN-PT and its evolution under an external field behave like a normal ferroelectric material, the domain structure and domain evolution process of PSN appear to be abnormal for a ferroelectric, but consistent with the character of a relaxor.