Fabrication and characterisation of nanocrystalline composites of Ca1−xCoxMoO4 (x = 0, 0.3, 0.5, 0.7, 1) prepared by co-precipitation method as a humidity sensor

• Published in: Journal of materials science. Materials in electronics 2017-02, Vol.28 (4), p.3548-3559
• Main Authors: Jeseentharani, V., Jeyaraj, B., Dayalan, A., Nagaraja, K. S.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Materials Science; Optical and Electronic Materials
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-016-5956-5

The effect of substitution of scheelite structure of calcium–cobalt molybdate (CaCM, Ca 1−x Co x MoO 4 ; x = 0, 0.3, 0.5, 0.7, 1) for humidity sensor application was studied. The composites were prepared using a co-precipitation method with different mole ratios. As-prepared composites were studied by TG/DTA analyses to find out the sintering temperature of the prepared the composites. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed in order to identify phase composition and crystallite structure. The composites were characterised by Fourier Transform-Infrared spectroscopy, Fourier Transform-Raman spectroscopy, transmission electron microscopy (TEM) and UV–visible absorption spectroscopy. Surface area of composites was studied using Brunauer–Emmett–Teller (BET) analysis. The composites were subjected to solid-state dc electrical conductivity for humidity sensing at room temperature. The resistance measurements as a function of relative humidity (RH) in the range of 5–98% were carried out and the sensitivity factors ( S f  =  R 5% / R 98% ) were calculated. Our results showed high sensitivity (S f ) of Ca 0.7 Co 0.3 MoO 4 (CaCM-2) as 5252 ± 157 compared with that of the end composites CaMoO 4 (CaM-1) and CoMoO 4 (CoM-5). The response and recovery times of CaCM-2 showed 150 and 110 s, respectively.