Comparative study on micromorphology and humidity sensitive properties of thin-film and thick-film humidity sensors based on semiconducting MnWO4

Qu, Wanyuan; Włodarski, W.; Meyer, J.-U.

doi:10.1016/s0925-4005(99)00487-6

Cited by 145 publications

(66 citation statements)

References 5 publications

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“…The second polarization mechanism is switched on at RH 20%, approximately. Then as RH increases, above RH 50%, the electrolytic charge transport in the condensed water within the pores and the charge transfer to the walls of the pores starts to become important and only through a sort of Warburg impedance [22,23] our results can be explained. Then, see (Figs.…”

Section: Discussionmentioning

confidence: 78%

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Humidity sensing properties of a thick-film titania prepared by a slow spinning process

Faia

Furtado

Ferreira

2004

Sensors and Actuators B: Chemical

127

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A ceramic thick film humidity sensor was produced from an emulsion of titania powders by a spin coating technique using a low speed. Electrical measurements were taken between interdigital electrodes obtained by depositing silver paste on the oxide, then cured at 500 • C for 15 min. Different relative humidities of a dynamic atmosphere were obtained by mixing dry and 23 • C saturated synthetic air in convenient proportions. Complex impedance spectra of the titania sensor at various relative humidities (RH) and different temperatures were measured and compared. The humidity sensing behaviour is due to surface water molecules adsorption and capillary condensation. The proposed sensing mechanisms, explaining the registered impedance spectra, are a combination of proton hopping, hydronium electrical drift and diffusion, and electrolytic conduction. In the frequency range 1-400 Hz, resistance and capacitive reactance show variations of three to four-order magnitude over the RH range 10-100%. The curves representing the variations of resistance and capacitive reactance versus RH show clearly the existence of two dominant electrical charge transport mechanisms. A parameter called characteristic humidity is defined to represent the sensitive response of the sensor. It was found that the sensitivity was highly dependent on the frequency. This work also shows that, for the same RH, both resistance and capacitive reactance vary with the atmosphere temperature.

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Section: Discussionmentioning

confidence: 78%

“…The charge transport occurs when H 3 O + ions release a proton to neighbouring water molecules, which accepts it while releasing another proton and so on. This is known as the Grotthuss's chain reaction [7,21,22]. At higher humidity levels physisorbed water layers show a liquid-like behaviour and H + ions move freely.…”

Section: Discussionmentioning

confidence: 99%

Humidity sensing properties of a thick-film titania prepared by a slow spinning process

Faia

Furtado

Ferreira

2004

Sensors and Actuators B: Chemical

127

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“…An electrolytic conduction in condensed water will take place in addition to the protonic transport in the physisorbed layers [11]. This succession of mechanisms leads to a rapid increase in conduction (decrease in resistance) with increasing humidity content.…”

Section: Humidity Sensitivitymentioning

confidence: 99%

A Ceramic Thick Film Humidity Sensor Based on MnZn Ferrite

Arshaka

Twomey

Egan

2002

Sensors

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A ceramic thick film humidity sensor, produced from MnZn ferrite, is presented. The proposed sensing mechanism is a combination of proton hopping, hydronium diffusion, and vacancy donor traps releasing electrons into the conduction band. The sensor structure comprises a two-layer device; the first layer is an interdigitated conductor and the second layer is a 30µm thick sensing layer. The effects of sintering the sensing pastes in air and vacuum have been reported. The air-fired sample exhibits the highest humidity sensitivity (1.54%/RH%) and the lowest temperature sensitivity (0.37%/ o C). The vacuum-fired sample has the lowest humidity sensitivity (0.043%/RH) and the highest temperature sensitivity (0.77%/ o C). The sensitivity results indicate that the air-fired sample has the best potential for use in humidity sensing applications.

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“…7,8 The second tungstate oxides exhibit a wolframite-type monoclinic structure where both M and W atoms are bonded to six oxygen atoms, which results in the formation of octahedral [MO 6 ]/[WO 6 ] clusters. 9,10 These differences in the coordination/structure cause defects in the crystal lattice and the appearance of photocatalytic, 11,12 photoluminescence (PL), [13][14][15][16] humidity sensor [17][18][19] and magnetic properties 20,21 as well as electronic properties for the tungstates.…”

Section: Introductionmentioning

confidence: 99%

Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO4 nanocrystals

et al. 2012

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Comparative study on micromorphology and humidity sensitive properties of thin-film and thick-film humidity sensors based on semiconducting MnWO4

Cited by 145 publications

References 5 publications

Humidity sensing properties of a thick-film titania prepared by a slow spinning process

Humidity sensing properties of a thick-film titania prepared by a slow spinning process

A Ceramic Thick Film Humidity Sensor Based on MnZn Ferrite

Effect of partial preferential orientation and distortions in octahedral clusters on the photoluminescence properties of FeWO4 nanocrystals

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