Influence of Ni2+ and Sn4+ substitution on gas sensing behaviour of zinc ferrite thick films

Nanocrystalline ferrite powders of Ni (x) Zn1 - x + y Fe2-2y Sn (y) O-4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0 and y = 0.1, 0.2) were prepared by oxalate co-precipitation method and characterized by XRD, FT-IR and FE-SEM techniques. The ferrite thick films (FTFs) of all compositions were prepared by screen printing technique and tested for gas sensing behaviour for liquid petroleum gas (LPG), ethanol (C2H5OH) and chlorine (Cl-2). For LPG, the sensitivity decreases with an increase in Ni2+ up to x = 0.6. It increases slightly for further increment in Ni2+. For this gas, the sensitivity is higher for higher concentration of Sn4+ (y = 0.2) while the optimum temperatures are smaller than that for lower concentration of Sn4+ (y = 0.1). The response and recovery times increase with the increase in Ni2+ for lower concentration of Sn4+ (y = 0.1), while at higher concentration of Sn4+ (y = 0.2), there is increase (for Ni2+ up to x = 0.6) and decrease (for further increase in Ni2+ up to 1.0) in response and recovery times. For ethanol and Cl-2, the sensitivity of Zn FTFs decreases with an increase in Ni2+ and increases with an increase in Sn4+. For these gases, the optimum temperature is found to be higher for higher concentration of Sn4+. The response and recovery times of Zn FTFs for ethanol and Cl-2 increase with increasing Ni2+ and Sn4+.