Raman scattering in HfxZr1−xO2 nanoparticles

Raman spectroscopy demonstrates that ,5 nm dimension HfxZr1−xO2 nanocrystals prepared by a nonhydrolytic sol-gel synthesis method are solid solutions of hafnia and zirconia, with no discernable segregation within the individual nanoparticles. Zirconia-rich particles are tetragonal and ensembles of hafnia-rich particles show mixed tetragonal/monoclinic phases. Sintering at 1200 °C produces larger particles s20–30 nmd that are monoclinic. A simple lattice dynamics model with composition-averaged cation mass and scaled force constants is used to understand how the Raman mode frequencies vary with composition in the tetragonal HfxZr1−xO2 nanoparticles. Background luminescence from these particles is minimized after oxygen treatment, suggesting possible oxygen defects in the as-prepared particles. Raman scattering is also used to estimate composition and the relative fractions of tetragonal and monoclinic phases. In some regimes there are mixed phases, and Raman analysis suggests that in these regimes the tetragonal phase particles are relatively rich in zirconium and the monoclinic phase particles are relatively rich in hafnium.