Cerium(IV) oxide – zinc oxide nanocomposites have attracted considerable attention for gas-sensing applications owing to their favourable structural, electronic, and catalytic characteristics. In this study, CeO₂–ZnO composite gas sensors were fabricated using hydrothermally prepared powders followed by a thick-film screen-printing process. The structural and morphological properties of the materials were systematically examined using scanning electron microscopy (SEM), and X-ray diffraction (XRD). The analyses confirmed high crystallinity, uniform surface morphology, compact microstructure, and well-defined phase development. XRD patterns indicated the coexistence of the hexagonal wurtzite structure of ZnO and the cubic fluorite structure of CeO₂, verifying the successful formation of a hetero-structured composite. The sensing characteristics of the fabricated devices were evaluated against several reducing gases, including ethanol, liquefied petroleum gas (LPG), and ammonia. Among the investigated compositions, the 2 wt% CeO₂–ZnO composite demonstrated the best sensing performance toward ethanol, delivering a response of approximately 94% at an optimal operating temperature of 325 °C. In addition, it exhibited shorter response and recovery times compared with pure ZnO-based sensors. The enhanced sensing behaviour is attributed to the synergistic interaction between CeO₂ and ZnO, which promotes higher surface reactivity, increased oxygen vacancy concentration, and improved catalytic activity, thereby accelerating adsorption–desorption dynamics. Furthermore, CeO₂, ZnO, and CeO₂/ZnO core–shell nanostructures were also synthesized via a facile and economical chemical combustion route without the use of stabilizing agents. This method provided advantages such as high phase purity, rapid synthesis, homogeneous particle distribution, and the avoidance of complex instrumentation. The sensor displayed optimal performance at 120 °C, achieving a sensitivity of about 70% toward hydrogen sulphide (H₂S), which was notably superior to that of individual ZnO or CeO₂ sensors. Overall, the CeO₂–ZnO nanocomposite sensors exhibited improved sensitivity, rapid response–recovery behaviour, good stability, and reproducible performance.

Keywords: Cerium(IV) Oxide–Zinc Oxide Nanocomposites; Sol Gel; Gas Sensor; Nanocrystal;