Effects of Annealing Temperature on Phase Transformation of CoTiO₃ Nanoparticles and on their Structural, Optical, and Magnetic Properties

Cobalt titanate (CoTiO₃) nanoparticles have been prepared by annealing of precursor molecules obtained from a mixture of titanium isopropoxide with cobalt nitrate and glacial acetic acid by sol-gel method. The structural properties of nanoparticles were investigated by X-ray diffraction (XRD) and Raman spectroscopy to determine the phase composition and crystallite size. The optical properties of the nanoparticles were characterized by UV-Vis absorption spectra. XRD and Raman analysis confirmed that CoTiO₃ phase was present at annealing temperatures above 700 °C. For the investigation of the elemental compositions and chemical binding configurations, the samples were analyzed by X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the morphology and particle sizes and were found to be between 70 and 90 nm. The samples annealed at temperatures equal or higher than 600 °C exhibited paramagnetic behavior, whereas those annealed at or above 700 °C exhibited superparamagnetic behavior as shown by vibrating sample magnetometer at room temperature.