Glycine combusted ZnFe2O4 gas sensor: Evaluation of structural, morphological and gas response properties

A simple and robust synthesis approach to zinc based spinel ferrite (ZnFe2O4) using the glycine combustion method is reported. The route utilizes divalent zinc nitrate (Zn(NO3)2·6H2O) and trivalent iron nitrate (Fe(NO3)3·9H2O) precursors in aqueous solution (distilled H2O). Glycine (NH2–CH2–COOH) acts as a fuel for the combustion process and subsequent ferrite (ZnFe2O4) formation. As produced material powder was sintered at 700 °C in the pellet form and examined for LPG, acetone, ethanol and ammonia sensing properties in the temperature range of 200–450 °C. XRD and TEM analyses revealed the formation of single phase nanocrystalline material with crystallite size in the range of 25–30 nm. SEM analysis confirmed the coarse structural morphology due to auto-ignition during the combustion reaction. The produced ferrite showed maximum response to both acetone (57%) and LPG (54%) at operating temperatures of 250 °C and 375 °C, respectively. Further, the sensor showed decent stability and reproducibility towards LPG and acetone, over the period of 30 days, which was then decreased by 2% up to 45 days. The present study confirms that the as produced ZnFe2O4 is a promising candidate for fabricating high performance sensors towards LPG and acetone sensing, in practice.