Microwave-assisted solid-state route for low-activation-energy phase formation and grain growth kinetics in nanocrystalline ZnFe₂O₄ photocatalyst
摘要
Nanocrystalline ZnFe₂O₄ (ZFO) particles were synthesized using a microwave-assisted solid-state reaction (MW–SSR), and their phase formation kinetics were systematically investigated. Differential scanning calorimetry revealed an exceptionally low activation energy for crystallization (~ 5.1 kJ·mol⁻1), several times lower than values reported for conventional solid-state reaction method. This reduction highlights the strong influence of microwave irradiation in accelerating spinel phase formation. In contrast, the activation energy for grain growth (~ 38 kJ·mol⁻1) was found to be higher than in conventional methods, suggesting that microwave processing promotes rapid nucleation while suppressing coarsening, thereby stabilizing nanoscale crystallites (~ 35 nm). Structural and optical analyses confirmed phase-pure ZFO with a bandgap of ~ 1.9 eV, while morphological studies showed uniform particle distribution. Photocatalytic tests on methylene blue degradation demonstrated visible-light activity comparable to solid-state synthesized ZFO. These findings extend new kinetic insights into microwave-driven crystallization and growth to the past studies. The results establish MW–SSR method as a rapid, energy-efficient, and scalable approach for fabricating functional ferrites with potential applications in photocatalysis and related areas.