PREPARATION AND CHARACTERIZATION OF HAFNI UM ZIRCONIUM AND TITANIUM-OXIDE POWDERS FROM OXALIC PRECURSORS

This paper deals with the preparation preparation of oxalic complexes H-2[Hf1-xMxO(C2O4)2], yH-2O (M=Zr or Ti), precursors of ceramics in th e HfO2-ZrO2 and HfO2-TiO2 systems, and with the characterization of ox ides obtained at low temperature. The influence of the introduction of yttrium oxide in these systems was studied, leading to metastable tet ragonal phases formation at lower temperatures. Thermal analysis of th e complexes have been performed by DTA and TGA. The powder specimens p roduced after the pyrolysis have been caracterized by X-ray diffractio n, scanning electron microscopy and granulometric distribution analysi s.