Abstract
Polycrystalline samples with general formula Yb2-xCrxO3 (0<x<0.03), obtained by sot-gel method and analyzed by X-ray diffraction, formed solid solutions over all the mentioned range. Cr showed a maximum solubility of 2.8 mol% in Yb2O3 sesquioxide at 1000 degrees C. A preferential substitution of Cr3+ ions over two cationic sites, 8b and 24d in the space group Ia-3 was found. The lattice parameters a are found to vary linearly (10.4402(4) angstrom < a < 10.4372(1) angstrom) with the composition x. The two independent atoms Yb/Cr have octahedral coordination; however, the degrees of distortion of their coordination polyhedron are different. Replacing Yb3+ by Cr3+ introduces slight changes in the atomic coordinates leading to an increase of the mean cation-anion distances. The ability of Raman spectroscopy to detect changes in local coordination is utilized. A pseudo-tetrahedral coordination for the Cr3+ in the 24d site was found. Magnetic susceptibility measurements of all samples were done in a temperature range of 2-50 K. For T < 37 K, the inverse paramagnetic susceptibilities depend linearly on temperature. However, in the high-temperature region, for T > 37K, the inverse paramagnetic susceptibilities are non-linear versus temperature. This deviation from the Curie-Weiss behaviour was discussed. (C) 2011 Elsevier Inc. All rights reserved.