Enhanced High-Temperature (600 °C) NO Response of ZnFeO Nanoparticle-Based Exhaust Gas Sensors.

Fabrication of gas sensors to monitor toxic exhaust gases at high working temperatures is a challenging task due to the low sensitivity and narrow long-term stability of the devices under harsh conditions. Herein, the fabrication of a chemiresistor-type gas sensor is reported for the detection of NO gas at 600 °C. The sensing element consists of ZnFeO nanoparticles prepared via a high-energy ball milling and annealed at different temperatures (600-1000 °C). The effects of annealing temperature on the crystal structure, morphology, and gas sensing properties of ZnFeO nanoparticles are studied. A mixed spinel structure of ZnFeO nanoparticles with a lattice parameter of 8.445 Å is revealed by X-ray diffraction analysis. The crystallite size and X-ray density of ZnFeO nanoparticles increase with the annealing temperature, whereas the lattice parameter and volume are considerably reduced indicating lattice distortion and defects such as oxygen vacancies. ZnFeO nanoparticles annealed at 1000 °C exhibit the highest sensitivity (0.13% ppm), sharp response ( = 195 s), recovery ( = 17 s), and linear response to 100-400 ppm NO gas. The annealing temperature and oxygen vacancies play a major role in determining the sensitivity of devices. The plausible sensing mechanism is discussed. ZnFeO nanoparticles show great potential for high-temperature exhaust gas sensing applications.