Internal distortion in ceria-doped hafnia solid solutions: High-resolutionx-ray diffraction and Raman scattering - art. no. 134104

High-resolution synchrotron x-ray powder diffraction and Raman scattering h ave indicated the existence of tetragonal ceria-doped hafnia with both an a xial ratio c(f)/a(f) of unity and internal shear defomation. The values of c(f)/a(f) ratio in HfO2-X-mol %-CeO2 samples (X= 80, 85, and 90) are estima ted to be 1 +/-0.000 04 from the estimated standard deviation of the peak p ositions and to be 1 +/-0.002 from the full width at half maximum of the 40 0(f) reflection peaks. However, the Raman spectra of these samples clearly demonstrate the tetragonal phase. The intensity of the Raman band around 28 0 cm(-1), which is one of the characteristic bands of the tetragonal phase, continuously decreased and approached zero between X=90 and 95, which refl ects the tetragonal-cubic phase boundary is located within this composition al range. The lattice distortion does not induce the cubic-tetragonal phase transition but an internal distortion in oxygen sublattice, oxygen displac ement along the c(f) axis from the ideal fluorite position, does.