Chemical and microstructural characterisation of HfO2-Y2O3 ceramics with high amount of Y2O3 (33, 40 and 50 mol. %) manufactured using spark plasma sintering

Hafnia based ceramics are potential promising candidates to be used as thermal barrier coatings (TBC) for ap-plications in the field of propulsion. In this study, Spark Plasma Sintering (SPS) of fully stabilised hafnia with yttrium oxide (yttria) was investigated to provide a better understanding of the effect of manufacturing pa-rameters, on the crystallography, chemistry and microstructure of the material. Several hafnia powders, con-taining different amounts of yttria (33 mol. %, 40 mol. % or 50 mol. %), were sintered by SPS at different temperature levels ranging from 1600 degrees C to 1850 degrees C. On these materials, X-ray diffraction patterns associated with scanning electron micrographs have highlighted the influence of both the sintering temperature and the amount of yttria on the final composition, the lattice parameter and the microstructure of hafnia-based materials. In the end, it is established that, for all quantities of yttrium employed, the main phase is Y2Hf2O7 with very high densification levels.