Solution combustion synthesis of zinc and calcium aluminate spinel phase materials: optical and structural properties

In this experimental study, zinc aluminate and calcium aluminate spinel nano-powders were synthesized using the solution combustion method. Subsequently, we explored the impact of metal cation substitution (Zn⁺² and Ca⁺²) on the optical and structural properties of these samples through ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction analysis (XRD). Crystalline forms of ZnAl₂O₄ and CoAl₂O₄ were obtained after calcination at 900 °C for 4 h under atmospheric air conditions. The UV–visible spectroscopy results revealed optical bandgap values of 3.771 and 3.507 eV for ZnAl₂O₄ and CaAl₂O₄ respectively. The FT-IR spectra demonstrated the presence of intense fundamental absorption peaks in the wavenumbers range 400–745 cm⁻¹, confirming the formation of metal aluminate spinel structure. The X-ray diffraction analysis confirmed the spinel structure of the prepared samples. Furthermore, the XRD results revealed that the variation of the M element in the structure led to change in the lattice type and the crystallite size, which is ranged from 26.003 to 42.001 nm. These findings indicate that these compounds are promising candidates for a range of optoelectronic applications.