A study of the ZrO2-Fe2O3 system by XRD, Fe-57 Mossbauer and vibrational spectroscopies

Samples at the ZrO2-rich side of the ZrO2-Fe2O3 system were prepared from a morphous precursors, precipitated from solutions of Zr(OC3H7)(4) and Fe(NO3 )(3). 9H(2)O and after their calcination at 500 degrees C, 800 degrees C an d 1100 degrees C 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 th eir segregation into an alpha-Fe2O3 phase were determined by Mossbauer spec troscopy. It was found that the Fe3+ ions appear in two different ZrO2-type solid solutions, Z(m) and Z(c), closely related structurally to m-ZrO2 and c-ZrO2, respectively. The volume fraction of the Z(c) phase increases with an increase in the iron content and a decrease in the temperature. The sol ubility of Fe2O3 in the ZrO2 lattice decreases with an increase in temperat ure. The terminal solid solubility limits of Fe2O3 in ZrO2 were estimated t o be 6.0 +/- 0.5 mol% at 500 degrees C, 4.0 +/- 0.5 mol% at 800 degrees C a nd less than 1 mol% at 1100 degrees C. The influence of the preparation che mistry on the formation of solid solutions was discussed. (C) 1999 Elsevier Science B.V. All rights reserved.