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

Abstract

Abstract. 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.

Multifrequency EPR study of Cr3+ions in LiScGeO4

“…For Fe 3+ with S = 5/2 useful structural information can be obtained from the topological (pseudosymmetry) analysis of the fourth rank ZFS tensor [22,23,26]. Additional confirmation of our present conclusion on the Cr 3+ substituting for Sc 3+ would be possible by performing the full diagonalization of the crystal field Hamiltonian [32,33] within the 3d 3 configuration as in the case of Cr 3+ in aluminosilicates [34,35]. This procedure involves the optical parameters, which are not available at present for the Cr-doped LiScGeO 4 .…”

Superposition model analysis from polarized electronic absorption spectra of Co2+in trigonally distorted octahedra in brucite-type Co(OH)2

“…Hence, the necessary intrinsic and power law exponent parameters for application to systems containing d-block elements, for example in geosciences, are practically missing or were obtained from natural, dilute phases, where the local structure around the particular transition ion is not exactly known (e.g. Cr 3+ in alumosilicates (Qin et al 1994). In order to provide reliable SM parameters of 3d n elements for future applications in geosciences, we started to investigate inorganic model compounds, i.e.…”

EMR study and superposition model analysis of Cr3+ and Fe3+ impurity ions in mullite powders used in aerospace industry

“…Standardization of orthorhombic and monoclinic ZFS (as well as crystal fi eld) parameters [23,24] will be considered in a full paper. Preliminary results for the impurity Cr 3+ and Fig.…”