Characterization of ZnAl₂O₄ Spinel Obtained by Hydrothermal and Microwave Assisted Combustion Method: A Comparative Study

Abstract

In this work, zinc aluminate spinel was prepared by two methods of directly synthesis (without calcination): microwave assisted combustion and hydrothermal method. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N₂-adsorption/desorption isotherms. The XRD patterns confirmed the formation of cubic ZnAl₂O₄ spinel structure with no secondary phases for both synthesis routes, whereas the hydrothermal method yielded powders with crystallite size 3 times smaller (6.9 nm), as compared to the powders produced by microwave assisted combustion method (25.6 nm). The micrographs revealed agglomerated powders with plate-like morphologies for both routes. Nitrogen adsorption/desorption isotherms (BET) revealed higher surface area (183 m².g^-1) and greater pore volume (0.173 cm³.g^-1) for ZnAl₂O₄ powders prepared by the hydrothermal method.

Keywords:
Zinc Aluminate; Hydrothermal Method; Microwave Assisted Combustion