Cation ordering in cubic and monoclinic : an x-ray powder diffraction and magnetic susceptibility study

Mixed sesquioxides Y2-xEuxO3 (x = 0.10, 0.20, 0.60, 1.00, 1.60 and 1.80) in the cubic (C) phase were obtained by precipitation and subsequent sintering. Cubic Eu2O3 and Y0.20Eu1.80O3 were transformed into monoclinic (B) phases at 1400 K and 1600 K respectively. The transformation is reconstructive in character. All of the structures were refined using the Rietveld powder method, and the Eu3+ ions found to be randomly distributed. The molar magnetic susceptibilities at room temperature exceed the free-ion values, and are almost independent of the concentration for x greater than or equal to 0.60. For x less than or equal to 0.20, the susceptibilities decrease with decreasing concentration of the magnetic ion Eu3+. This behaviour is attributed to crystal-field and anisotropic exchange effects.