SURFACE CHARACTERIZATION OF YTTRIA-STABILIZED TETRAGONAL ZRO2 .1. STRUCTURAL, MORPHOLOGICAL, AND SURFACE HYDRATION FEATURES

The characterization of three microcrystalline Y2O3-stabilized tetrago nal zirconia (t-ZrO2) preparations was carried out by BET, XRD, HRTEM, and FTIR spectroscopy, and revealed that morphological and surface fe atures of t-ZrO2 specimens depend, much more than in the case of the m onoclinic modification (m-ZrO2), on the preparative history of the mat erial. Preparations fired at T less-than-or-equal-to 1000 K are mostly made up of coin-like particles terminating with the same crystal plan e and present only one surface OH species, but after firing at higher temperatures crystal shape and morphology of the various preparations start changing appreciably and differing from one another. The morphol ogical changes are also monitored by changes in the IR spectrum of the surface OH layer, which becomes quite similar to that of the microcry stalline m-ZrO2 phase. After firing at T greater-than-or-equal-to 1173 K, some of the t-ZrO2 preparations will generate to various extents ( depending on the Y2O3 content and on the preparative procedure) an amo rphous phase coating the particles. This modification can be monitored by appreciable changes in the IR spectrum of the surface OH layer.