Morphotropic phase boundary in (1−x)BiFeO3–xPbTiO3: phase coexistence region and unusually large tetragonality

Abstract

It is shown that the tetragonal (T) and rhombohedral (R) structures of (1−x)BiFeO3–xPbTiO3 are stable for xT⩾0.31 and xR⩽0.27, respectively, giving the narrowest width of 0.03, reported so far, for the morphotropic phase boundary region in this system. The Rietveld refined structure of the T phase for x=0.31 reveals partial covalent character of the Ti∕Fe–O and Pb∕Bi–O bonds which may be responsible for the unusually large tetragonality.