Thermal behavior of the amorphous precursors of the ZrO2-GaO1.5 system

• Published in: Journal of alloys and compounds Vol. 460; no. 1-2; pp. 444 - 452
• Main Authors: STEFANIC, G, MUSIC, S
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier 28.07.2008
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from solid phases (including multiphase diffusion and recrystallization); Materials science; Methods of crystal growth; physics of crystal growth; Physics; Scanning electron microscopy; Raman spectra; Crystallization; Gallium oxide; X-ray diffraction; Differential thermal analysis; XRD; Amorphous state; Gallium additions; Heat treatments; Phase transitions; Field emission electron microscopy; Zirconium oxide; Aqueous solutions; Phase stability; SEM; Thermal analysis; Solubility limit; Oxide materials; Coprecipitation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2007.05.075

The amorphous precursors of the ZrO2-GaO1.5 system on 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 (DTA), X-ray powder diffraction (XRD), Raman spectroscopy and field emission scanning electron microscopy (FE-SEM). Crystallization temperature of the amorphous precursors rose with an increase in the GaO1.5 content, from 405 deg C (0 mol% GaO1.5) to 720 deg C (50 mol% GaO1.5). The results of Rietveld refinements indicated that the maximum solubility of Ga3+ ions in the ZrO2 lattice (43 mol%) occurred in the metastable products obtained after crystallization of the amorphous precursors. Further thermal treatment caused a decrease of the solubility limits, which became negligible after calcination at 1100 deg C. The results of Raman spectroscopy showed that the incorporation of Ga3+ ions partially stabilized the tetragonal polymorph of ZrO2, but could not stabilize its cubic polymorph. The incorporation of Ga3+ ions caused a linear decrease in the unit-cell volume of the ZrO2-type solid solutions, but the rate of the decrease turned out to be smaller than the rate obtained after the incorporation of bigger Fe3+ ions.