Antimony substitution leading to structural transformation (Bixbyite→ Fluorite) and altering the optical band gap in Y2O3

Abstract

The transformation of ordered bixbyite structured Y2O3 to cation disordered fluorite structure is demonstrated by antimony substitution in the present work. The samples are prepared by the wet chemical method and characterized by employing various physicochemical techniques. The superstructure reflections of bixbyite were observed for samples prepared with 10 mol% of antimony, beyond which the structure transformed into a disordered fluorite structure. The diffracted peaks became broad in the powder X-ray diffraction pattern with increasing antimony concentration. The Williamson-Hall analysis indicated compressive strain in antimony substituted samples. Microscopy and Raman spectral measurements confirmed this structural transformation. The antimony existed in the III oxidation state, as revealed by XPS measurements. The optical bandgap of Y2O3 changed from 4.81 to 3.62, and 3.20 eV for 20 and 50 mol% antimony substituted samples. In the photoluminescence emission spectrum, the transitions of the excited Jahn-Teller state of Sb3+ are observed in the visible region. 50 mol% antimony substituted yttria sample catalyzed the complete degradation of aqueous rhodamine-6G (Rh-6G) in 105 min, assisted by the UV–visible radiation. The reaction followed pseudo-first-order kinetics, and the catalyst showed nearly the same efficiency up to five times of its reuse. The recovered catalyst did not undergo any change in its structure.