ZnCo_{(2−<i>x</i>)}Ce_<i>x</i>O₄, (<i>x</i>=0–1.0 wt%): optimized structural, morphological, dielectric, and magnetic properties for humidity sensing applications

In this article ZnCo_(2-<i>x</i>)Ce _<i>x</i> O₄ doped Ce was prepared by the sol-gel process where <i>x</i> = 0, 0.2, 0.5, and 1 wt%. The samples were investigated by XRD, SEM, FTIR, VSM, and dielectric studies. XRD shows the dominance of the cubic structure with an intense peak at 36°. SEM showed that the material changed from densely packed particles to flaky, porous structures. SEM results signify undoped samples having a pure ceramic microstructure with dense, well-packed particles. In contrast, doped samples reflect the residence particles and flaky features with more spaces between particles. FTIR showed two main peaks at 557 cm^-1 and 660 cm^-1 from Co-O and Zn-O stretching. When Ce was added, these peaks shifted and got weaker, showing that the structure became less ordered. The dielectric properties showed very high charge storage at low frequencies due to charges building up at boundaries. Ce doping made the charge storage lower and less sensitive to temperature. The combined para- and slight ferromagnetic nature is initiated with the highest cerium content (SCe1.0). The conductivity showed a flat region at low frequencies, and then increased following a power law. Ce doping made conductivity much lower. Sample SCe0.5 exhibited a distinctive conductivity feature because it had a good balance of trapped and free charges. Medium Ce levels (SCe0.2 and SCe0.5) led to balanced properties good for applications like supercapacitors and sensors. The application of the composite as a humidity sensor demonstrated high repeatability throughout a range of humidity levels (11-84% RH). The response and recovery times are 800 and 20 s, respectively.