Synthesis and optical characterization of In3+-stabilized γ-Bi2O3 sillenite semiconductor with cation deficiency

Bi3+-containing semiconductors usually show rich optical and electronic properties due to the hybridization between 6s and 6p electronic components together with the lone pair in Bi3+ ions. In this work, an In3+-stabilized γ-Bi2O3 sillenite structure, Bi24InO37.5 (Bi12In0.5O18.75), was prepared through the facile sol-gel method. The samples developed into ball-like nanoparticles with size of 200-300 nm. The Rietveld structure refinement was performed. Bi24InO37.5 belongs to cubic sillenite-structure of metastable cubic γ-Bi2O3 (space group I23), a well-known group of non-centrosymmetric crystal. The morphological characteristics were tested by SEM, TEM, EDS and Brunauer-Emmett-Teller (BET) measurements. The optical absorption, band gap energy and electronic structures were discussed. In contrast to the reference Bi2O3, Bi24InO37.5 shows a narrower band energy of 2.48 eV. Meanwhile, it has a self-activated emission with a low luminescence quenching.