Solid State Electrical Conductivity and Humidity Sensing Properties of Cr2O3-MoO3 Composites

Abstract

Experimental results on the composites made from Cr2O3 (CO) and MoO3 (MO) for electrical and humidity‐sensing properties are described. The compound and composites of Cr2O3 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 composites were identified by powder XRD data. The composites were subjected to dc resistance measurements as a function of relative humidity in the range of 5–98%, achieved by different water vapor buffers thermostated at room temperature. The sensitivity factor, Sf (R5%/R98%) measured at 25 °C revealed that COMO‐32 has the highest humidity sensitivity 8.08 × 103 for which the response and recovery time have been studied. The scanning electron microscope (SEM) showed the porous structure of the composite.

Electronic to protonic conduction switching in Cu2O nanostructured porous films: the effect of humidity exposure

“…Most of the studies available reported on composite semiconducting oxides. [25][26][27][28][29] For example, Hsueh et al 25 reported the fabrication of a humidity sensor by growing CuO nanowires (NWs) on the surface of a glass substrate. The results showed that the sensitivity of the sensor increased with increasing RH level, which was due to the p-type nature of the CuO NWs.…”

“…A similar conclusion was reported by Pokhrel and Nagaraja in the case of Cr 2 O 3 -MoO 3 composites exposed to humid conditions. 28 Recently, Wang et al 29 reported the humidity-sensing properties of sea urchin-like CuO modied by reduced graphene oxide (rGO). When they compared the performance in terms of response time and RH value at relatively high humidity conditions, they found that the sensor based on the CuO/rGO composite performed better than the sensors fabricated using pure CuO and rGO.…”

Influence of Lithium Insertion on the Electronic Transport in Electroactive MoO3 Nanobelts and Classical Powders: Morphological and Particle Size Effects

“…Dc conductivity of α-MoO 3 has been previously investigated for single crystals, powders, and thin films. Conductivity of single crystal was measured perpendicular to molybdenum trioxide sheets with a value of about 10 −10 S·cm −1 and that of pressed or sintered classical powders between 10 −10 and 10 −3 S·cm −1 . − Differences in stoichiometry and in sintering processes can lead to such differences in conductivity. Conductivity of aggregated powder of nanobelts was estimated at 10 −5 S·cm −1 .…”

Evolution of Anodic Product from Molybdenum Metal in Absolute Ethanol and Humidity Sensing under Ambient Conditions

“…Sensors are widely used in environmental monitoring, industrial/agricultural production, and daily lives − and sensors based on nanosized metal oxides, such as SnO 2 , CeO 2 , and perovskites, are popular ones for humidity sensing. − MoO 3 has been used in the humidity sensing of trimethylamine, , ammonia, ethanol, volatile organic compounds (VOCs), , and hydrogen, , but it can also be used for humidity sensing, using the facile resistivity technique. − The α-MoO 3 -based humidity sensor has been prepared via the evaporation of Mo 0 under an O 2 atmosphere, , and MoO 3 plays a major role in enhancing the humidity sensing performance of composites due to the variation of microstructure and the water adsorption kinetics in the composite sensor with oxides ,− , of NiO, Cr 2 O 3 , WO 3 , etc. Mo VI oxide in the highest oxidation state shows different crystalline phases, depending on the synthetic routes: − four metastable phases have been reported for MoO 3 at high temperature or high pressure, in addition to the stable orthorhombic two-dimensional (2-D) α-MoO 3 phase. , For example, hexagonal molybdenum trioxide, which is a metastable phase that transforms to α-MoO 3 above 425 °C, has been reported to have a formula ranging from MoO 3 to MoO 3 · n H 2 O (0.09 ≤ n ≤ 0.69) and allows a versatile intercalation chemistry with interesting chemical, electrochemical, and catalytic properties. ,, The systematic study of the phase evolution of MoO 3 under different moisture and reducing/oxidation conditions would benefit the design and understanding of humidity sensing.…”