Optical, electrical, and catalytic (photo-and sono-) properties of indium doped γ-Bi2O3 with Sillenite structure

The exotic structure and properties exhibited by the metastable solids are exemplified adequately in the materials chemistry area. In this report, metastable gamma-Bi2O3 has been stabilized without adding any impurity by the auto-combustion method and compared with the changes in structure and optical property brought out by the inclusion of In3+ ions. Compositions doped with indium (7 and 10 mol% in place of bismuth) resulted in stoichiometric Sillenite-type structures as revealed by their powder X-ray diffraction patterns, FTIR, and Raman spectral measurements. The pale yellow gamma-Bi2O3 acquired pale brown coloration on indium inclusion, and the intensities varied with varying indium content. Optical bandgap reduction from 2.63 (pure gamma-Bi2O3) to 2.41 eV occurred when 10 mol% of indium was doped in place of bismuth. The formation of non-stoichiometric Sillenite structures was noticed in samples with higher indium concentrations (up to 50 mol%). The non-stoichiometric samples displayed intense brown color and showed a drastic reduction in the optical bandgap, reaching values as low as 1.57 eV (50 mol% indium doped sample). From XPS analysis and red-ox titrations, nearly 5% of oxygen excess was estimated for the non-stoichiometric samples doped with indium. The BET surface area of indium doped non-stoichiometric Sillenites (126 m(2)/g) was higher than indium doped stoichiometric Sillenites (74 m2/g). The oxygen ion conductivity studies of pure gamma-Bi2O3 and indium doped non-stoichiometric Sillenites revealed a marginal rise in conductivity with indium inclusion. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study stabilized metastable gamma-Bi2O3 without impurities and investigated the effects of indium ion doping on its structure and optical properties. Doping with indium resulted in changes in color and optical bandgap, with non-stoichiometric samples exhibiting lower bandgap values. Additionally, indium-doped non-stoichiometric Sillenites displayed higher BET surface area and slightly increased oxygen ion conductivity compared to stoichiometric counterparts.