Fabrication and characterization of Ru-doped LiCuFe2O4 nanoparticles and their capacitive and resistive humidity sensor applications

Polycrystalline ruthenium-doped lithium-copper-ferrite (Ru - LiCuFe2O4)nanoparticles (NPs) are synthesized using a simple and cost-effective chemical co-precipitation method and annealed at different temperatures for increasing the crystallinity. The transmission and scanning electron microscopy images have confirmed the presence of soft agglomerations and cuboids for the samples annealed at 1100 degrees C. X-ray photoelectron results along with Raman spectra have collectively demonstrated the presence of Ru in the structure of Ru - LiCuFe2O4 NPs. The dielectric properties of as-synthesized Ru - LiCuFe2O4 NPs are investigated using LCR meter where the smaller NPs demonstrates a higher dielectric constant. Also, the results of magnetic measurements of annealed Ru - LiCuFe2O4 NPs have corroborated a soft magnetic nature due to the pinning sites that endow lower coercivity, remanence and saturation magnetization than that of the pristine one. The variation of permittivity and electrical resistivity with respect to frequency under humidity conditions suggested that this material has a potential to use as capacitive and resistive humidity sensor. The results of this study open the doors for utilization of metal-doped magnetic ferrites for humidity sensing applications.