Crystal structure analysis of epitaxial BiFeO3-BiCoO3 solid solution films grown by metalorganic chemical vapor deposition

Epitaxial (001)-oriented (1-x)BiFeO3-xBiCoO(3) solid solution films with x = 0-0.33 were grown on (100)SrTiO3 substrates at 700 degrees C by metalorganic chemical vapor deposition. The crystal structure of the films was characterized by high-resolution X-ray diffraction analysis and Raman spectroscopy. Unit cell volume and the lattice parameter were changed with increasing x. The BiFeo(3) film with x = 0 has rhombohedral symmetry and those with x = 0.16 and 0.21 have a mixture of rhombohedral and tetragonal symmetries. Finally, tetragonal symmetry was observed for the film with x = 0.33 together with a small amount of the contamination phase. This result suggests that the symmetry of (1-x)BiFeO3-xBiCOO(3) films changed from rhombohedral to tetragonal with increasing x similarly to Pb(Zr,Ti)O-3 having a large piezo response.