부산대학교 도서관

Cobalt doped SnO2 nanoparticles were prepared for different molar concentration 2%, 4% & 6% of Co by Chemical co precipitation method. The prepared samples were characterized by X-ray diffraction (XRD), UV-visible absorption spectra, Photoluminescence (PL), High Resolution transmission electron microscopy (HRTEM) and Vibrating sample magnetometer for their Structural, Optical and Magnetic Properties. The doping concentration of Co induces crystal phase, crystallite size, lattice distortion, optical and magnetic properties were investigated. XRD Results showed that Co2+ replaces Sn4+ in the crystal lattice of SnO2, which enhanced the growth of crystallite size and suppressed the transformation from anatase to rutile phase due to lattice distortion produced in SnO2. The UV absorption studies concluded the band gap of Co doped SnO2 nanoparticles decreased from 3.79 eV to 3.62 eV in visible region. PL spectra exhibit only a broad emission peak in the range of 420 nm to 540 nm and excitation is observed at the wavelength of 385 nm. New energy levels are not formed in the band structure to produce new emission due to Co doping and also indicates that the substitution of Co2+ ions for Sn4+ ions without the formation of other additional energy levels. Due to increasing Co concentration in SnO2, the emission energies are decreasing the peak intensities. An efficient method for inducing the ferromagnetic behavior from increasing the Co concentration from 2% to 6 % was known from the magnetization versus magnetic field (M--H) curves at room temperature of the Co doped SnO2 samples. The dominant magnetic interaction between Co ions, and hence, the ferromagnetic behaviour increases for increase in Co2+ doping concentration.Consequently, to achieve the good ferromagnetic character in these materials, the concentration of Co dopant has to be properly optimized. [ABSTRACT FROM AUTHOR]