BULK, SURFACE AND DOUBLE-LAYER PROPERTIES OF ZIRCONIA POLYMORPHS SUBJECTED TO MECHANICAL TREATMENTS

Zirconia (ZrO2) may exist in different polymorphs. At low pressures and for temperatures as high as congruent-to 1150-degrees-C only the stable phase has the monoclinic structure; tetragonal and cubic oxides form however, as metastable phases together with the monoclinic in the lower temperature region (up to ca. 600 - 800-degrees-C). By combining stages of calcination (of a hydrothermal precursor) with severe grinding treatments of the powders it was possible to obtain pure phase monoclinic oxides (S. Ardizzone, G. Bassi, G. Liborio, Colloids and Surfaces 51 (1990) 207). This paper reports results concerning the effects specifically induced by the severe grinding on the phase composition, on the state of the surface and on the interfacial electrostatic reactivity of the powders. The effects produced by ageing, calcinations and further mechanical treatments of the samples are also examined by the same techniques i.e. by X-ray diffraction, XPS determinations and surface charge measurements.