Co⁺³ substituted gadolinium nano-orthoferrites for environmental monitoring: Synthesis, device fabrication, and detailed gas sensing performance

The development of gas sensors with high sensitivity, stability, and selectivity is vital in detecting hazardous gas leaks and monitoring air pollution. The perovskite comprises a stable chemical structure and offers multifunctional properties to act as a base for several device engineering. Specifically, perovskites possess a great potential for chemical sensors with their semiconducting nature and ease to dope with other elements to further improve gas sensing properties. In this present study, a rare-earth gadolinium orthoferrite, GdFeO₃ (GFO), and Co-doped GFO were systematically investigated by evaluating their structural, morphological, electrical, and gas sensing properties. A high-temperature solid-state reaction synthesized the phase-pure compounds. The magnetic properties of Co-doped GFO significantly improved than pure GFO. The pellet-type gas sensor was fabricated, which does not need any sophisticated instrumentation such as microfabrication. When exposed to 20 ppm of NO₂ gas, a GdFe_0.7Co_0.3O₃ (GFOC3) device gave 6.86% response at 200 ˚C, along with a response time of 104 s and the recovery time of 97 s. Additionally, Co-doped GFO sensors showed a detectable response even at room temperature, enabling- practical applications in an ambient environment. The gas sensor revealed stable gas response characteristics even after several months. Therefore, this study elucidates that the Co-doped GFO has better gas sensing performance compared to a bare GFO and that it is highly selective towards the NO₂ gas.