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 (% R
H
) for Cu
.2
Zn
.8
Fe
2
O
4
and Cu
.8
Zn
.2
Fe
2
O
4
ferrites doped with 0.01%, 0.05% and 0.1% CaCl
2
was investigated. With the increase in %R
H
, the resistivity decreased exponentially up to 60% R
H
and linearly beyond 60% R
H
. For Cu
.2
Zn
.8
Fe
2
O
4
, the resistivity values found to be much higher as compared to Cu
.8
Zn.2Fe
2
O
4
for all doping concentrations of CaCl
2
. With higher Zn content, i. e. for Cu
.2
Zn
.8
Fe
2
O
4
, 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.2Fe
2
O
4
which has less Zn content showed different trend. For this system, with the increase in doping percentage of CaCl
2
, the resistivity found to be increased where as the sensitivity found to be decreased.