Correlation of micro-structure with the opto-electronic properties of the sol-gel derived powder Sn1-xCdxO2 nanoparticles

Abstract

Powdered cadmium substituted tin oxide (Sn1-xCdxO2) nanoparticles (NPs) with various Cd2+ ion concentrations (0%–30%) were synthesized via sol-gel route. The X-ray diffraction (XRD) and high resolution transmission electron microscopic (HRTEM) results justified the nanocrystallinity of the samples as the mean crystallite sizes were found within 16 nm–38 nm. The Williamson – Hall (W – H) analysis was employed for determining the relation between the lattice strain and crystallite size of the powder NPs. The monotonous decrease of lattice strain is consistent with the increase of crystallite size by increase in Cd2+ substitution concentration. The substitution of Sn4+ with Cd2+ caused an increase of particle size with the increase of Cd2+ concentration. The energy dispersive X-ray spectroscopic (EDS) studies indicated the presence of cadmium ion in the Cd-substituted SnO2 powder NPs. Further, the Fourier-transform infrared (FT-IR) spectra of the powder samples registered the distinct absorbance band dips highlighting the atomic vibrations. The optical absorption (OA) spectra revealed that the band gap energies (Eg) decreased with the increase in Cd2+ substitution levels. The positron annihilation lifetime (PAL) spectroscopic analysis based on the vacancy type defects which were present in abundance in the powder NPs and played vital roles to modify their properties. The photo-induced luminescence properties were studied by fluorescence (FL) spectroscopy based on defects and/or oxygen vacancies associated with the emission transitions. The results suggested the feasibility of tailoring the characteristics of Cd-substituted SnO2 NPs synthesized through sol-gel route for various technological applications.