engleski

A study of the ZrO2–Fe2O3 system by XRD, 57Fe Mössbauer and vibrational spectroscopies

Samples at the ZrO2-rich side of the ZrO2-Fe2O3 system were prepared from amorphous precursors, precipitated from solutions of Zr(OC3H7)4 and Fe(NO3)3ˇ9H2O and after their calcination at 500, 800 and 1100oC. X-ray powder diffraction and laser Raman spectroscopy were used to investigate the phase composition and the solid solubility limits. The status of the Fe3+ ions in the ZrO2-type lattice and the process of their segregation into an a-Fe2O3 phase were determined by Mössbauer spectroscopy. It was found that the Fe3+ ions appear in two different ZrO2-type solid solutions, Zm and Zc, closely related structurally to m-ZrO2 and c-ZrO2, respectively. The volume fraction of the Zc phase increases with an increase in the iron content and a decrease in the temperature. The solubility of Fe2O3 in the ZrO2 lattice decreases with an increase in temperature. The terminal solid solubility limits of Fe2O3 in ZrO2 were estimated to (6.0ą0.5) mole % at 500oC, (4.0ą0.5) mole % at 800oC and less then 1 mole % at 1100 oC. The influence of the preparation chemistry on the formation of solid solutions was discussed.

ZrO2–Fe2O3 system ; Mössbauer ; XRD ; Raman ; solid state solubility

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