Local Structures and Raman Spectra in the Ca(Zr,Ti)O3 Perovskite Solid Solutions

Abstract

Local structures and cation distributions in perovskite Ca(Zr,Ti)O{sub 3} solid solutions were analyzed using X-ray absorption fine structure and pair-distribution functions obtained from total neutron scattering. The analyses revealed that the Zr-O and Ti-O bond distances in the solid solutions remain distinct and close to their respective values in the end-compounds, CaZrO{sub 3} and CaTiO{sub 3}. The structural strain in the solid solutions, which results from the ionic size mismatch between Zr and Ti, is accommodated by adjustment of the tilting angles for the different [BO6] octahedra. Additionally, the octahedra are distorted by bending, which affects the O-O distances while preserving a uniform distribution of the B-O distances. Combined experimental and theoretical analyses of Raman spectra demonstrated that high-frequency modes associated with the breathing of oxygen octahedra arise even in the nearly disordered solid solutions. Our results suggest a coexistence of both localized and extended Raman-active breathing vibrations, associated with the octahedra hosting the minority and majority B-cations, respectively. For the dilute solid solutions (<25 at. %), these modes yield two well-resolved Raman peaks.