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Armalcolite, a current motivated rare earth ceramic usually available in the moon, had been used for the first time, as dielectric-type humidity sensors. The armalcolite nanocomposite was prepared using multistep solid-state sintering under high pressure and a high-sensitive dielectric sensor was developed for humidity controlling applications. Different concerning phases developed by the proper sintering were analyzed precisely by X-ray diffraction (XRD) as well as scanning electron microscopy (SEM). At 100 Hz frequency, the obtained dielectric constant was 24 times greater at 95% relative humidity (RH) as compared to 33% RH. The armalcolite-based sensor showed lower hysteresis (<3.5%), good stability, and faster response (~18 seconds) and recovery (~35 seconds) times compared to conventional humidity sensors. The sensing mechanism of the nanocomposite was categorically determined by the analyzed characteristics parameters such as dielectric constants, normalized loss tangent, and alternating current conductivity properties. This study also confirmed that the whole conduction mechanism was accomplished by electrons or ions and dipoles in the entire RH range. Therefore, the present armalcolite-based porous nanocomposite would be a potential sensing material for novel humidity sensors. [ABSTRACT FROM AUTHOR]

Since humidity sensors have been widely used in many sectors, a suitable humidity sensing material with improved sensitivity, faster response and recovery times, better stability and low hysteresis is necessary to be developed. Here, we fabricate a uniformly porous humidity sensor using Ca, Ti substituted Mg ferrites with chemical formula of CaMgFe1.33Ti3O12 as humidity sensing materials by solid-sate step-sintering technique. This synthesis technique is useful to control the grain size with increased porosity to enhance the hydrophilic characteristics of the CaMgFe1.33Ti3O12 nanoceramic based sintered electro-ceramic nanocomposites. The highest porosity, lowest density and excellent surface-hydrophilicity properties were obtained at 1050 °C sintered ceramic. The performance of this impedance type humidity sensor was evaluated by electrical characterizations using alternating current (AC) in the 33%-95% relative humidity (RH) range at 25 °C. Compared with existing conventional resistive humidity sensors, the present sintered electro-ceramic nanocomposite based humidity sensor showed faster response time (20 s) and recovery time (40 s). This newly developed sensor showed extremely high sensitivity (%S) and small hysteresis of <3.4%. Long-term stability of the sensor had been determined by testing for 30 consecutive days. Therefore, the high performance sensing behavior of the present electro-ceramic nanocomposites would be suitable for a potential use in advanced humidity sensors. [ABSTRACT FROM AUTHOR]