Atomic scale study of oxidation of hafnium: Formation of hafnium core and oxide shell

Abstract

Perturbed angular correlation studies on hafnium foil subjected to annealing in oxygen atmosphere show that there exists three distinct Hf sites which are identified as probe atoms associated with hafnium metallic clusters, hafnium oxide, and oxygen deficient oxide zones. Kinetics of oxidation has been studied. Variations of quadrupole parameters with annealing treatments show that there is a formation of hafnium core surrounded by a shell of hafnium oxide. Inner hafnium core and outer oxide shell are identified to be separated by oxygen deficient oxide zones. Results suggest that annealing at elevated temperatures leads to a reduction in the size of hafnium cores to submicron, surrounded predominantly by well grown hafnium oxide. Occurrence of nanometallic hafnium clusters in the hafnium oxide matrix has been identified by low frequency laser Raman scattering studies.