engleski

Influence of Cr2O3 on the stability of low temperature t-ZrO2

Aqueous solutions containing different molar fractions of Cr(NO3)3ˇ9H2O and ZrO(NO3)2ˇ2H2O salts were dried at 110 oC for 24 hours and calcinated up to 1100 oC. Precise X-ray powder diffraction measurements of the obtained samples, covering the whole concentration region in the system ZrO2-Cr2O3, were performed. It was found that the solubility of Cr2O3 in ZrO2, as well as the solubility of ZrO2 in Cr2O3, was negligible. Except for the end samples, identified as pure m-ZrO2 and Cr2O3, other samples contained the phases Cr2O3, m-ZrO2 and metastable t-ZrO2. The fraction of the t-ZrO2 phase in the total content of ZrO2 (m-ZrO2 + t-ZrO2) increased with an increase of the initial content of Cr2O3 but this relation was not linear. The observed stabilization of metastable t-ZrO2 could not be attributed to the formation of a solid solution. It was suggested that the stabilization of t-ZrO2 at room temperature resulted from a very strong surface interaction between chromium oxide and zirconia. This interaction prevented the diffusion of oxygen from the atmosphere into the ZrO2 lattice, which otherwise triggers the transition t-ZrO2Žm-ZrO2 on cooling.

T-zro2-cr2o3 system; Phase relation; Phase transformation; Solid-solubility

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