engleski

THERMAL BEHAVIOR OF THE AMORPHOUS PRECURSORS IN THE ZrO2-GaO1.5 SYSTEM

The amorphous precursors of the ZrO2-GaO1.5 system at the ZrO2-rich side of the concentration range were prepared by the co-precipitation from aqueous solutions of the corresponding salts. Thermal behaviour of the amorphous precursors was monitored using differential thermal analysis, X-ray powder diffraction (XRD) and Raman spectroscopy. The crystallization temperature of the amorphous precursors increased with an increase in the GaO1.5 content, from 435 °C (0 mol % of GaO1.5) to 720 °C (50 mol % of GaO1.5). The results of phase analysis indicated an extended capability for the incorporation of Ga3+ ions in the metastable ZrO2-type solid solution obtained after crystallization of amorphous co-gels. However, solubility significantly decreased with further temperature treatment. The results of XRD and Raman spectroscopy showed that the incorporation of Ga3+ ions partially stabilized only tetragonal polymorph of ZrO2. Precise determination of lattice parameters, performed using whole-powder-pattern decomposition method, showed that the unit-cell volume of t-ZrO2 type solid solutions decreases linearly with the increase of Ga3+ content. The obtained results were compared with the results obtained for some other trivalent undersized dopant cations (Al3+, Cr3+, and Fe3+).

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