Memorial Lecture for Dr. H. Okino

Dr. Okino´s contributions for piezoelectric application field will be introduced. First of all, by using piezoresponse force microscopy (PFM) and contact-resonance piezoresponse microscopy (CR-PFM), domain structures and domain-related properties of typical piezoelectric single crystal, for example PbTiO₃, Pb(Mg_1/3Nb_2/3)O₃ -PbTiO₃ single crystals, were successfully observed. Four kinds of domain structures (180 c-c, 180 a-a, 90 a-a and 90 a-c domains) on grown surfaces of PbTiO₃ single crystals were imaged successfully using vertical and lateral piezoresponse force microscopy (PFM). Next, the domain-structure images of (001) plates of Pb(Mg_1/3Nb_2/3)O₃ -PbTiO₃ (PMN-PT) single crystals were successfully observed in a vacuum using a contact-resonance piezoresponse force microscopy. The domain structures of (001) plates of (l-x) Pb(Mg_1/3Nb_2/3)O_3-xPbTiO₃ (PMN-PT) single crystals were obtained at room temperature after 240 thermal treatment at various cooling rates. PMN -32 % PT and PMN- 34 %PT single crystals undergoes a relaxor-ferroelectric phase transition from Tetragonal phase to the Cubic phase.