Electrical and humidity sensing properties of molybdenum(VI) oxide and tungsten(VI) oxide composites

Abstract

Experimental results on the composites made from WO3 (WO) and MoO3 (MO) for electrical and humidity-sensing properties are described. The compound and composites of WO3 and MoO3 in mole ratios (1:0, 0:1, 1:1, 1:2, 2:1, 3:2 and 1:4) were sintered in the form of the disc and subjected to dc conductance measurements over the temperature range 373–673 K from which the activation energies were determined. The biphasic nature of the composites was identified by powder XRD. The dc resistance of these hybrid oxides decreased on exposure to humidity at room temperature and the use of a mixture of oxides was found to be effective for optimizing humidity sensing performance in dc mode. The composite WOMO-21 has the highest humidity sensitivity (R5%/R98%), greater than 9 × 103, with a response and recovery time of approximately 320 and 200 s respectively, attributed mainly to the optimization of pore structure and its even distribution in a biphasic matrix which is a metastable mixture of the two phases WO3 and MoO3.