This paper describes an attempt to develop a ceramic humidity sensor having an approximately exponential dependency of its AC conductance on relative humidity and having a short response time. Ammonium paratungstate pentahydrate [(NH4)10W12O41.5H2O] and aluminium sulphate [Al2(SO4)3.16H2O] mixed in different wt% are used to make thick films. It is found that the AC conductance of the thick film with 40 wt% of ammonium paratungstate pentahydrate shows an almost exponential relationship with relative humidity. SEM and XRD studies are also carried out on the film to look at the nature and constituents of the samples.

 

Studies on ceramics for use as humidity sensors have been a field of research for the last two decades. Porous ceramics have been investigated and used as humidity sensors for consistency and durability. In particular, ammonium paratungstate pentahydrate (APT.5H2O) has consolidated its position as a humidity sensing material  and a humidity sensor. On the other hand, recent studies on aluminium sulphate, Al2(SO4)3.16H2O also enhance the possibility of its use as a humidity sensor. Here, the humidity dependency of the AC electrical conductance of thick films of APT mixed with aluminium sulphate in different proportions is investigated. The response time of the sensor is also measured. The SEM and XRD studies on the sample are carried out in order to know the structure of the samples and to identify the constituents of the samples. The results are presented and discussed in this paper.