A study of structural, morphological, optical and humidity sensing properties of CaCu3Ti4O12 powders synthesized by combustion method

Calcium Copper Titanate (CCTO) powder was synthesized via a low-cost facile combustion method at various calcination temperatures and times. The structural properties of the prepared CCTO powder were investigated from an X-ray diffraction (XRD) study, which confirmed the formation of the cubic phase with space group Im3. Further, Rietveld refinement of the XRD data was performed for the detailed structural analysis of the samples. The surface morphology of the CCTO powder was studied by Field Emission Scanning Electron Microscopy (FESEM), which showed an increase in particle size with an increase in the calcination temperature. The optical properties of the powders were examined by UV–vis Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence Spectroscopy. The optical bandgap values, estimated from Tauc’s plot, increase with the increase in calcination temperature due to the elimination of structural defects or localized states inside the bandgap. The porous single-phase CCTO ceramic was subjected to a homemade experimental set-up combined with an LCR meter to investigate its room temperature humidity sensing characteristics in capacitive mode at various operating frequencies. At 100 Hz, the obtained humidity response curve for the CCTO-based sensor showed a 560 % increment in capacitance as the Relative Humidity (RH) changed from 40 % to 90 %.