Ti and Fe Speciation by X-Ray Photoelectron Spectroscopy(XPS) and Mössbauer Spectroscopy for a Full Crystal Chemical Characterisation of Ti-Garnets from Colli Albani (Italy)
✍ Scribed by Emanuela Schingaro; Fernando Scordari; Giuseppe Pedrazzi; Cosimino Malitesta
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 233 KB
- Volume
- 94
- Category
- Article
- ISSN
- 0003-4592
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✦ Synopsis
Abstract
Different analytical and structural methods (Electron Probe Micro‐ Analysis, Single Crystal X‐ray diffraction, X‐ray Photoelectron Spectroscopy, Mössbauer spectroscopy) were combined to fully characterise the crystal chemistry of natural Ti‐bearing garnets from Colli Albani (Lazio, Italy). The study of the relevant complex crystal chemistry (large number of cation substitutions affecting the three independent X(8‐fold), Y(6‐fold) and Z(4‐fold) crystallographic sites and Fe and Ti transition elements exhibiting several oxidation states and coordination environments) benefited from the multi‐technique approach.
Electron probe microanalysis provided elemental composition of the analysed samples, which have low Ti‐content (TiO~2~ in the range 1.99 ‐ 3.48 wt %) and slightly different Fe/Al ratios. For all samples, two doublets were fitted to room temperature Mössbauer spectra and assigned to Fe^3+^(Y) (∼ 95%) and Fe^2+^(X) (∼ 5%). Up to three doublets (Ti^3+^(Y), Ti^4+^(Y), Ti^4+^(Z)) were fitted to XPS spectra and yielded direct evaluation of Ti site population. XPS technique confirmed its potential for the study of speciation of Ti in minerals.