Electrical and humidity sensing properties of Chromium(III) oxide–tungsten(VI) oxide composites

The composite made from the mixture of Cr2O3 and WO3 for humidity sensing properties are described in detail. The sintered Cr2O3 (COWO-10), WO3 (COWO-01), and the composites of CO and WO in the mole ratio 1:1, 1:2, 2:1, 3:2, and 1:4, respectively in the form of a disc of 10 mm diameter were subjected to dc conductance measurements over the temperature range 373–673 K from which activation energies were determined. The Brunauer–Emmett–Teller (BET) surface adsorption studies showed that the radius of the pore sizes were found to be distributed from 10–45 Å. The pore specific volume was calculated to be 0.01 cm3 gm−1, which was further evidenced by scanning electron microscopic photographs. As the composites having micropores are preferred for the humidity sensing properties, the composites were subjected to dc resistance measurements as a function of relative humidity in the range of 5–98% RH, achieved by different water vapor buffers thermostated at room temperature. The sensitivity factor, Sf (R5%/R98%) measured at 25 °C revealed that COWO-14 has the highest humidity sensitivity factor of 14039(±977). The response and recovery time for this humidity sensing composite was also studied.