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Article

Humidity Sensing Ceria Thin-Films

1
Faculty of Chemical Engineering and Technology, Marulićev trg 20, 10000 Zagreb, Croatia
2
Ruđer Bošković Institute, Bijenička Cesta 54, 10000 Zagreb, Croatia
3
College of Materials and Environmental Engineering, Hangzhou Dianzi University, 1158, No.2 Street, Hangzhou 310018, China
*
Authors to whom correspondence should be addressed.
Academic Editors: Marcin Runowski and Antonino Gulino
Nanomaterials 2022, 12(3), 521; https://doi.org/10.3390/nano12030521
Received: 7 December 2021 / Revised: 18 January 2022 / Accepted: 28 January 2022 / Published: 2 February 2022
Lowering the constitutive domains of semiconducting oxides to the nano-range has recently opened up the possibility of added benefit in the research area of sensing materials, in terms both of greater specific surface area and pore volume. Among such nanomaterials, ceria has attracted much attention; therefore, we chemically derived homogeneous ceria nanoparticle slurries. One set of samples was tape-casted onto a conducting glass substrate to form thin-films of various thicknesses, thereby avoiding demanding reaction conditions typical of physical depositions, while the other was pressed into pellets. Structural and microstructural features, along with electrical properties and derivative humidity-sensing performance of ceria thin-films and powders pressed into pellets, were studied in detail. Particular attention was given to solid-state impedance spectroscopy (SS-IS), under controlled relative humidity (RH) from 30%–85%, in a wide temperature and frequency range. Moreover, for the thin-film setup, measurements were performed in surface-mode and cross-section-mode. From the results, we extrapolated the influence of composition on relative humidity, the role of configuration and thin-film thickness on electrical properties, and derivative humidity-sensing performance. The structural analysis and depth profiling both point to monophasic crystalline ceria. Microstructure analysis reveals slightly agglomerated spherical particles and thin-films with low surface roughness. Under controlled humidity, the shape of the conductivity spectrum stays the same along with an increase in RH, and a notable shift to higher conductivity values. The relaxation is slow, as the thickness of the pellet slows the return of conductivity values. The increase in humidity has a positive effect on the overall DC conductivity, similar to the temperature effect for semiconducting behavior. As for the surface measurement setup, the thin-film thickness impacts the shape of the spectra and electrical processes. The surface measurement setup turns out to be more sensitive to relative humidity changes, emphasized with higher RH, along with an increase in thin-film thickness. The moisture directly affects the conductivity spectra in the dispersion part, i.e., on the localized short-range charge carriers. Moisture sensitivity is a reversible process for thin-film samples, in contrast to pellet form samples. View Full-Text
Keywords: thin-films; relative humidity sensors; ceria nanoparticles; solid-state impedance spectroscopy; grazing incidence X-ray diffraction (GIXRD); atomic force microscopy (AFM); field emission scanning electron microscopy (FESEM) thin-films; relative humidity sensors; ceria nanoparticles; solid-state impedance spectroscopy; grazing incidence X-ray diffraction (GIXRD); atomic force microscopy (AFM); field emission scanning electron microscopy (FESEM)
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MDPI and ACS Style

Mandić, V.; Bafti, A.; Pavić, L.; Panžić, I.; Kurajica, S.; Pavelić, J.-S.; Shi, Z.; Mužina, K.; Ivković, I.K. Humidity Sensing Ceria Thin-Films. Nanomaterials 2022, 12, 521. https://doi.org/10.3390/nano12030521

AMA Style

Mandić V, Bafti A, Pavić L, Panžić I, Kurajica S, Pavelić J-S, Shi Z, Mužina K, Ivković IK. Humidity Sensing Ceria Thin-Films. Nanomaterials. 2022; 12(3):521. https://doi.org/10.3390/nano12030521

Chicago/Turabian Style

Mandić, Vilko, Arijeta Bafti, Luka Pavić, Ivana Panžić, Stanislav Kurajica, Jakov-Stjepan Pavelić, Zhen Shi, Katarina Mužina, and Ivana Katarina Ivković. 2022. "Humidity Sensing Ceria Thin-Films" Nanomaterials 12, no. 3: 521. https://doi.org/10.3390/nano12030521

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