Ammonia sensing properties of V-doped ZnO:Ca nanopowders prepared by sol-gel synthesis

V-doped ZnO:Ca nanopowders with different V loading were prepared by sol-gel synthesis and successive drying in ethanol under supercritical conditions. Characterization data of nanopowders annealed at 700 degrees C in air, revealed that they have the wurtzite structure. Raman features of V-doped ZnO:Ca samples were found to be substantially modified with respect to pure ZnO or binary ZnO:Ca samples, which indicate the substitution of vanadium ions in the ZnO lattice. The ammonia sensing properties of V-doped ZnO:Ca thick films were also investigated. The results obtained demonstrate the possibility of a fine tuning of the sensing characteristics of ZnO-based sensors by Ca and V doping. In particular, their combined effect has brought to an enhanced response towards NH3 compared to bare ZnO and binary V-ZnO and Ca-ZnO samples. Raman investigation suggested that the presence of Ca play a key role in enhancing the sensor response in these ternary composite nanomaterials. (C) 2015 Elsevier Inc. All rights reserved.