Cubic-tetragonal phase change of yttria-doped hafnia solid solution: high-resolution X-ray diffraction and Raman scattering

High-resolution synchrotron X-ray powder diffraction and Raman scattering h ave demonstrated the existence of tetragonal yttria-doped hafnia solid solu tion with an axial ratio, c(f)/a(f), of unity, but having displacements alo ng the cf(-) axis from the ideal fluorite position in the oxygen sublattice . The values of c(f)/a(f) ratio in HfO2-X mol%YO1.5 samples (X = 13, 14, an d 16) are estimated to be unity with the precision of +/-0.00003 from the e stimated standard deviation of the peak position and less than +/-0.001 fro m the full-width at the half-maximum of the 400(f) reflection peak. However , the Raman spectra of the samples of X = 13, 14, and 16 clearly demonstrat e the tetragonal phase. (C) 2001 Elsevier Science B.V. All rights reserved.