engleski

Thermal behavior of the amorphous precursors of the ZrO2-CrO1.5 system

The amorphous precursors of the ZrO2-CrO1.5 system at the ZrO2-rich side of the concentration range were prepared by co-precipitation from aqueous solutions of the corresponding salts. Thermal behavior of the amorphous precursors was monitored using differential thermal analysis, XRD, Raman and FT-IR spectroscopies. The crystallization temperature of the amorphous precurssors increased with an increase in the CrO1.5 content, from 435 oC (0 mol % of CrO1.5) to 822 oC (50 mol % of CrO1.5). The results of phase analysis indicated an extended capability for the incorporation of Cr3+ ions into metastable ZrO2-type solid solution obtained after crystallization of amorphous co-gels. Maximum solubility of Cr3+ ions in the ZrO2 lattice, obtained after crystallization of amorphous precursors, was estimated at approx. 26 %, but significantly decreased with futher temperature treatment. The results of XRD and Raman spectroscopy showed that incorporation of Cr3+ ions partially stabilized only the tetragonal ZrO2 polymorph. The incorporation of Cr3+ ions caused a decrease in the unit-cell volume of the t-ZrO2-type solid-solutions, but the rate of decrease turned out to be smaller than the rate obtained after the incorporation of Fe3+ ions. The reason of such behavior was discussed.

ZrO2-CrO1.5 system ; DTA ; Raman ; XRD

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