Humidity sensing properties of nanocrystalline pseudobrookite (Fe2TiO5) based thick films

• Published in: Sensors and actuators. B, Chemical Vol. 277; pp. 654 - 664
• Main Authors: Nikolic, Maria Vesna, Vasiljevic, Zorka Z., Lukovic, Miloljub D., Pavlovic, Vera P., Vujancevic, Jelena, Radovanovic, Milan, Krstic, Jugoslav B., Vlahovic, Branislav, Pavlovic, Vladimir B.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 20.12.2018; Elsevier Science Ltd
• Subjects: Acetic acid; Adhesives; Aluminum oxide; Anatase; Carrier mobility; Diffuse reflectance spectroscopy; Dispersants; Distilled water; Ethyl cellulose; Fe2TiO5; Field emission microscopy; Frequency ranges; Hematite; Humidity; Humidity sensor; Impedance; Measurement; Minerals; Nanocrystals; Photoelectrons; Pseudobrookite; Raman spectroscopy; Relative humidity; Scanning electron microscopy; Sensors; Spectrum analysis; Substrates; Thick film; Thick films; Transmission electron microscopy; Weight; X ray photoelectron spectroscopy; X-ray diffraction; Humidity sensor; Pseudobrookite; Fe2TiO5; Thick film
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2018.09.063

[Display omitted] •Nanocrystalline pseudbrookite thick films.•High humidity sensing.•Fast response.•Short time delay. Pseudobrookite based nanopowder was obtained by solid state synthesis of starting hematite and anatase nanopowders in the weight ratio 55:45. Structural and morphological properties were analyzed using X-ray diffraction (XRD), BET, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV/Vis diffuse reflectance spectroscopy, Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) confirming the formation of nanocrystalline pseudobrookite. The obtained powder was mixed with a binder (ethyl cellulose), dispersant (α-terpinol) and adhesion agents (acetic acid and distilled water) to obtain a thick film paste. It was screen printed on alumina substrate with interdigitated PdAg electrodes and fired at 600 °C for 30 min. Formation of a porous nanocrystalline thick film structure was shown using Scanning electron microscopy (SEM), while Hall measurements enabled determination of carrier mobility. Change of impedance response in the frequency range 42 Hz–1 MHz with humidity was analyzed at room temperature (25 °C) and 50 °C in the relative humidity range 30–90% and 40–90%, respectively. At 42 Hz, and room temperature the impedance reduced ∼28 times, while at 50 °C it reduced ∼147 times in the relative humidity range 40–90%. The sensor showed rapid response (16 s) and relatively low hysteresis (8.39% at 25 °C and 2.64% at 50 °C) showing that this is a promising material for application in humidity sensing.