X-ray Photoelectron Spectroscopy, Raman and Humidity Sensing Properties of Sm3+ Doped CoCr2O4 for Humidity Sensor Applications

This research presents the structural, microstructural, Raman, XPS and humidity sensing behaviour of Sm3+ doped cobalt chromite (CoCr2O4). All samples are synthesized using solution combustion method with urea and glucose as fuels. The X-ray diffraction analysis confirms the single-phase formation with a spinel cubic structure. Field emission scanning electron microscopy micrographs revealed that the materials are porous and include soft agglomerations. Elemental analysis was performed using Energy-dispersive X-ray spectroscopy analysis, confirming the presence of Samarium (3+) in the Sm3+ doped CoCr2O4 samples. The oxidation state of each element was determined using X-ray photoelectron spectroscopy (XPS) for CoCr1.98Sm0.02O4 samples. The vibration bands identified by the Raman spectra confirm the formation of the spinel cubic structure. The electrical properties were measured by using an LCR meter, and it was observed that smaller crystallite size exhibits higher dielectric constant. All the electrical properties were found to increase with increasing samarium concentration. In humid conditions, this material's resistance to electricity and permittivity and permittivity changes with frequency, making it useful as a capacitive and resistive humidity sensor. The findings of this work pave the way for the use of metal-doped magnetic chromites in applications for humidity sensing.