Impact of Controlled Thermal Oxidation on Phase Transition and Tailoring Properties of Sb2S3/Sb2O3 Composites

The study investigates the synthesis and characterisation of the Sb2S3/Sb2O3 composite materials through thermal oxidation at 350 °C with varying heating times. The structural, morphology, and electrical behaviours were characterised using XRD, FT-IR, SEM, EDS, UV–Vis spectroscopy, PL, and EIS. The phase transformation from stibnite (Sb2S3) to Sb2O3 phases (senarmontite and valentinite) is observed and discussed. The FT-IR spectra confirm the presence of characteristic Sb–S and Sb–O vibrations. The absorbance spectrum reveals a shift in the energy bandgap (Eg) with values of 1.58–2.23 eV, indicating the compositional changes due to prolonged heating. The emergence of electron donor Sb5+ ions (at 541.36 eV) and Sb3+ (at 540 eV) was investigated in the XPS study. In association, PL emission at 560 nm is attributed to the oxidative transformation of Sb3+ to Sb5+, suggesting the redox transformations within the composite. EIS analysis reveals the fastest interfacial charge-transfer process in the 60 min—heated sample. As a result, the prolonged heating time influences the phase transition and composition, resulting in the properties tailoring of the Sb2S3/Sb2O3 composites.