STRUCTURAL AND SPECTRAL CHARACTERIZATION OF Co 2+ -AND Ni 2+ -DOPED CdO POWDER PREPARED FROM SOLUTION AT ROOM TEMPERATURE (original) (raw)

The mild and simple solution method was used for the synthesis of Co 2+-and Ni 2+-doped CdO powders at room temperature. The prepared powders were characterized using powder X-ray diffraction, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), optical absorption, and Fourier transform infrared spectroscopy (FTIR). From the powder X-ray diffraction patterns, it has been observed that the prepared Co 2+ and Ni 2+ ion-doped CdO powders belong to the cubic phase, and the evaluated average crystalline sizes of the powders are 20 and 14 nm, respectively. The SEM images and the EDS spectra show that the prepared powders are distributed over different sizes in the grain boundaries. Optical absorption studies allow determination of site symmetry of the metal ion with its ligands. The crystal fi eld (Dq) and inter-electronic repulsion (B and C) parameters have been evaluated from the optical absorption spectra. The FTIR spectra show the characteristic fundamental vibrations of the metal oxide and CdO. Introduction. Cadmium oxide (CdO) is a semiconductor with a band gap of 2.4 eV. It has excellent electrical, mechanical, and optical properties. It has a cubic crystal structure of high density (8150 kg/m 3) and melting point (1500 o C) with alternating Cd and O atoms located at lattice points. CdO is an n-type semiconductor and has been widely investigated owing to its potential applications in optical fi elds, photovoltaic cells, and transparent electrodes [1, 2]. So far a number of methods have been used to synthesize various nanostructures, including thermal evaporation [3, 4], chemical bath deposition [5], solvothermal synthesis [6] and plasma-assisted approach [7–9]. The opto-electrical properties of CdO could be controlled by doping with different metallic ions such as In, Sn, Al, Sc, Y, Tl, Fe, Sm, Dy, etc. [10–17]. It has been observed that doping with ions of a radius smaller than that for Cd 2+ results in an increase in the doped material conductivity. The addition of ions with ionic radii equal or larger than Cd 2+ does not sig-nifi cantly alter the lattice parameters. By introducing a magnetic element into a non-magnetic matrix, some special physical properties, such as the giant magneto-resistance effect and mixed magnetism, can appear because of the change in magnetism, structure, and electrical transport [18]. Zou et al. [19] have prepared CdO nanoparticles by the micro-emulsion method employing AOT reverse micelles. There is also a report of stearate-coated CdO nanoparticles of 5–10 nm size range, obtained by the micro-emulsion method starting from an aqueous solution of cadmium salt and stearic acid in xylene [20]. A new method to prepare CdO nanoparti-cles has been reported, wherein a cadmium precursor compound is decomposed under solvothermal [21, 22] conditions in the presence of a capping agent. For this purpose, the cadmium compound Cd(C 6 H 5 N 2 O 2) 2 was used as the precursor and CdO nanoparticles of different sizes were obtained using tri-n-octylphosphine oxide (TOPO) as the capping agent [23]. Among these methods, the mild and simple solution method is rather effective in realizing the diversifi ed forms of CdO nanostructures using aqueous and non-aqueous solutions. The advantage of this method compared with other mentioned techniques includes low process temperature, inexpensiveness, and the capability of controlling the morphology of metal oxide semiconductors.