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Non-stoichiometric spinel ferrites are attracting increasing interest for gas sensing because their electrical and surface properties can be altered through composition control. In this work, ZnxFe₂O₄ nanostructures with varying zinc content (0.95,1.00,1.05) were synthesized with a microwave-assisted coprecipitation method and investigated for the detection of toxic and flammable gases. The influence of non-stoichiometry on the structural, morphological, and electronic properties was examined using X-ray diffraction and transmission electron microscopy, confirming the formation of nanostructured spinel phases with controlled deviations from stoichiometry. Gas sensing measurements were performed against representative reducing gases at operating temperatures of 25 – 225°C. The results show that both zinc-deficient (x < 1) and zinc-rich (x > 1) compositions display markedly different sensing behaviors compared to stoichiometric ZnFe₂O₄ (x =1). In particular, the Zn-deficient sample (x = 0.95) exhibited the highest response of S = 2941.59 to LPG at 25°C, with a response (97s) and recovery (303s) times. These findings indicate that modifying the Zn:Fe ratio changs defect chemistry, and surface adsorption sites, thereby enhancing selectivity. Overall, the study demonstrates that controlled non-stoichiometry in ZnxFe₂O₄ nanostructures is an effective strategy for improving sensitivity and stability in toxic and flammable gas detection, making them strong candidates for environmental monitoring and industrial safety applications.
