Ordered LiGa5O8 loaded with redox capable Cu2+, Cr3+ ions to manifest interesting optical, magnetic, and catalytic properties

The crystal structure and associated property changes brought about by substituting Cu2+ and Cr3+ ions for Li+ and Ga3+ ions, respectively, in ordered LiGa5O8 are probed in the present work. The samples were synthesized by a single-step calcination process of epoxide-mediated xerogels rapidly and characterized extensively. Powder X-ray diffraction patterns revealed the preservation of the superstructure of spinel up to 50 mol % Cu2+ with Li+, 20 mol % Cr3+ with Ga3+ and coupled substitution of Cu2+ (25 mol %) and Cr3+ (5 mol %) with Li and Ga, respectively. The structural refinements and electron microscopic analysis (high-resolution transmission electron microscopy and selected area electron diffraction) confirmed the samples’ ordered spinel structure. Raman and FTIR features confirmed the lower symmetry arising from the cation ordering in the samples. UV–visible and electron paramagnetic resonance spectroscopy measurements on Cu- and Cr-containing samples revealed their oxidation state and site preferences. Reversible peaks in DSC heating and cooling traces showed order/disorder phase transition in Cu2+(1069 and 1044 °C)- and Cr3+(1100 and 1038 °C) substituted samples. Photoemission in the red region and antiferromagnetic behavior with a Neel temperature of 8 K were displayed by the Cr-containing LiGa5O8. The Cu2+-substituted samples catalyzed the reduction of the nitroaromatics while Cr3+-containing sample catalyzed the photodegradation of Rh-6G dye solution. The coupled substituted sample (Cu/Cr), being advantageous, could perform both catalytic conversions.