Effect of doping concentration of CaCl2 and Zn content on the Cu - Zn humidity sensor

Variation of dc electrical resistivity with respect to percentage relative humidity (% RH) for Cu.2Zn.8Fe2O4 and Cu.8 Zn.2Fe2O4 ferrites doped with 0.01%, 0.05% and 0.1% CaCl2 was investigated. With the increase in %RH, the resistivity decreased exponentially up to 60% RH and linearly beyond 60% RH. For Cu.2Zn.8Fe2O4, the resistivity values found to be much higher as compared to Cu.8 Zn.2Fe2O4 for all doping concentrations of CaCl2. With higher Zn content, i. e. for Cu.2Zn.8Fe2O4, the resistivity as well as sensitivity decreased with the increase in doping percentage from 0.01% to 0.05% but increased again with the further increase in doping percentage to 0.1%. However, Cu.8 Zn.2Fe2O4 which has less Zn content showed different trend. For this system, with the increase in doping percentage of CaCl2, the resistivity found to be increased where as the sensitivity found to be decreased.