Piezoelectric properties of {100}-oriented epitaxial BiCoO3-BiFeO3 films measured using synchrotron x-ray diffraction

Electric polarization and the strain of {100}- oriented epitaxial BiFeO3 and BiFeO3-BiCoO3 films grown on (100)cSrRuO3 // (100)SrTiO3 substrates were simultaneously measured using synchrotron X-ray diffraction. The apparent piezoelectric coefficient d33,obs values of BiFeO3 and BiFeO3-BiCoO3 films were 28 and 63 pm/V, while the observed electrostrictive coefficient Q11,obs values of the films calculated from electric polarization and strain were 1.4x10-2 and 3.6x10-2 m4/C2, respectively. These results implied that the films become soft by the addition of BiCoO3 into BiFeO3. (author)