Hydrogen sensitivity of doped CuO/ZnO heterocontact sensors

Heterocontact sensors based on p-type CuO and n-type ZnO ceramics have been shown to exhibit a high sensitivity to reducing gas species and an intrinsic selectivity. In this work, doped heterocontact sensors were prepared via solid state synthesis routes. CuO was doped with various monovalent (Li, Na) and isovalent (Ca, Sr, Ni) dopants at different compositions to form both single phase and two phase samples. Effects of dopants on hydrogen sensitivity through conductivity and heterogeneous microstructure were investigated using dc current-voltage measurements and ac impedance analysis. It was observed that both monovalent and divalent dopants increased the hydrogen sensitivity significantly. The highest sensitivity was observed in a 2.5 mol% Ni-CuO/ZnO heterocontact and low amounts of Li doping were shown to greatly enhance the rectifying characteristics.