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

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

Bariloche

Conferencia; XIII International Conference on Solid Films and Surfaces; 2006

A film of HfO2-14 mol% CaO prepared by sol-gel has been grown on Al2O3 by deep coating. The thermal behavior of the film is investigated by using Differential Thermal Analyses (DTA-TGA), X-ray difraction (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 in order to find out the role of the atmospheric oxygen in the stability of the film. The as-prepared film exhibits a cubic structure (XRD) also revealed by the predominat hyperfine interaction determined by PAC. PAC results in air also showed the existence of another two components, one of them associated to CaHf4O9. The thermal evolution of the starting phase content evolved to the appearance of the monoclinic phase above 800°C in agreeament with subtle changes observed in DTA recorded in air. The differences between PAC results in air and vaccum and DTA in air and Ar, allowed interpreting the unknown interaction as due to processes occuring at the free surface of the film and also to understand why, in vaccum, the monoclinic phase did not appear.