Thermal study of the local structures in a HfO2-14 mol % CaO film

M.A. TAYLOR, P.C. RIVAS, O. DE SANCTIS, A.M. RODRIGUEZ, A.F. PASQUEVICH, J.A. MARTINEZ AND M.C. CARACOCHE

Bariloche, Argentna

Conferencia; 13th International Conference on Solid Films and Surface; 2006

A film of HfO2-14 mol% CaO prepared by sol-gel has been grown onto Al2O3 by deep coating. The thermal behavior of the film is investigated by using Differential Thermal Analyses (DTA-TGA), X-ray diffraction (XRD) as a function of annealing temperatures and the Perturbed Angular Correlation (PAC) technique in- temperature and after annealing. XRD experiments were performed in air, DTA in air and Ar and PAC in air and vacuum. The as-prepared film exhibits a cubic structure (XRD) and a predominant cubic hyperfine interaction (PAC in air). PAC results in air also show the existence of two other components, one of them associated to CaHf4O9 and the other, unknown. The thermal evolution of the starting phase content evolved to the appearance of the monoclinic phase above 800ºC in agreement with subtle changes observed in DTA recorded in air. The differences between PAC results in air and vacuum and between DTA in air and Ar, allowed interpreting the unknown interaction as due to processes occurring at the free surface of the film and also to understand why, in vacuum, the monoclinic phase does not appear.