Synthesis and Characterization of the Orthorhombic Sn₃O₄ Polymorph

Abstract

An unexplored tin oxide crystal phase (Sn3O4) was experimentally synthesized via a facile hydrothermal method. After tuning the often‐neglected parameters for the hydrothermal synthesis, namely the degree of filling of the precursor solution and the gas composition in the reactor head space, an unreported X‐ray diffraction pattern was discovered. Through various characterization studies, such as Rietveld analysis, energy dispersive X‐ray spectroscopy, and first‐principles calculations, this novel material was characterized as orthorhombic mixed‐valence tin oxide with the composition SnII2SnIVO4. This orthorhombic tin oxide is a new polymorph of Sn3O4, which differs from the reported conventional monoclinic structure. Computational and experimental analyses showed that orthorhombic Sn3O4 has a smaller band gap (2.0 eV), enabling greater absorption of visible light. This study is expected to improve the accuracy of hydrothermal synthesis and aid the discovery of new oxide materials.