CHROMIUM AS A PROBE IN AMORPHOUS AND SINGLE-CRYSTAL ZIRCONIA

The spectral properties of amorphous ZrO2. nH(2)O:Cr prepared by preci pitation from aqueous solution and those of cubic single crystals of y ttrium stabilised zirconia (YSZ) containing Cr(III) obtained by the sk ull method were studied. Cr(III) was used as a probe for the local env ironment. Its UV/Vis and luminescence spectra were recorded in both ma trices. The absorption spectrum of a single crystal of YSZ:Cr(III) was measured at 20 K. The temperature dependence of the luminescence of Z rO2. 33% Y2O3:Cr(III) and ZrO2. nH(2)O:Cr(III) was determined between 20 and 150 K. Heat treatment of the ZrO2. nH(2)O:Cr(III) between 400 a nd 1000 degrees C yielded tetragonal or monoclinic ZrO2:Cr microcrysta ls with average crystallite sizes of 15-45 nm. The powder samples were characterised by XRD and IR spectroscopy. Keating in air oxidised the incorporated chromium at T greater than or equal to 250 degrees C. Th e ZrO2. 33% Y2O3:Cr single crystal was only partially oxidised at 1000 degrees C. A qualitative physicochemical explanation for the incorpor ation and oxidation of Cr(III) in the zirconia matrices is proposed.