Ordered LiGa.sub.5O.sub.8 loaded with redox capable Cu.sup.2+, Cr.sup.3+ ions to manifest interesting optical, magnetic, and catalytic properties

• Published in: Journal of materials science 2021-12, Vol.56 (36), p.20111
• Main Authors: Yadav, Priyanka, Uniyal, Shrishti, Uma, Sitharaman, Nagarajan, Rajamani
• Format: Article
• Language: English
• Subjects: Analysis; Crystals; Diffraction; Spinel group; Structure; X-rays
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-021-06572-z

The crystal structure and associated property changes brought about by substituting Cu.sup.2+ and Cr.sup.3+ ions for Li.sup.+ and Ga.sup.3+ ions, respectively, in ordered LiGa.sub.5O.sub.8 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 % Cu.sup.2+ with Li.sup.+, 20 mol % Cr.sup.3+ with Ga.sup.3+ and coupled substitution of Cu.sup.2+ (25 mol %) and Cr.sup.3+ (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 Cu.sup.2+(1069 and 1044 °C)- and Cr.sup.3+(1100 and 1038 °C) substituted samples. Photoemission in the red region and antiferromagnetic behavior with a Néel temperature of 8 K were displayed by the Cr-containing LiGa.sub.5O.sub.8. The Cu.sup.2+-substituted samples catalyzed the reduction of the nitroaromatics while Cr.sup.3+-containing sample catalyzed the photodegradation of Rh-6G dye solution. The coupled substituted sample (Cu/Cr), being advantageous, could perform both catalytic conversions.