Correlation of spectroscopic properties and substitutional sites of Cr3+in aluminosilicates: II. Andalusite and sillimanite

✍ Scribed by J. Qin; C. Rudowicz; Y. M. Chang; Y. Y. Yeung

• Publisher: Springer-Verlag
• Year: 1994
• Tongue: English
• Weight: 676 KB
• Volume: 21
• Category: Article
• ISSN: 0342-1791
• DOI: 10.1007/bf00203928

✦ Synopsis

This paper is an extension of the earlier one dealing with kyanite in which the best fitting value of the oxygen ligand distance for Cr 3+ is adopted to study the spectroscopic properties of Cr 3 + ions doped at the two possible A1 sites in the other two polymorphs of the aluminosilicate group (A120 3 9 SiO2), namely, andalusite and sillimanite. The superposition model and the crystal field analysis package recently developed for 3d ions doped at arbitrary low symmetry sites in crystals are used to predict energy levels and statevectors within the whole 3d 3 configuration. Then the values of the ground state zerofield splitting for Cr 3+ ions at each A1 sites in the two crystals are obtained. The splittings of the lower excited states 2E and 4T 2 as well as the admixture of 4T 2 into 2E have also been predicted. Comparison of our results with the available experimental data enable us to correlate the optical and EPR spectroscopic properties with the substitutional Cr 3 § sites. The conclusion is that in andalusite and sillimanite only the A1 sites with nearly-octahedral six-fold coordination seem to be occupied by Cr 3+ ions.