Study of the Structural, Optical, Dielectric and Magnetic Properties of Copper-Doped SnO2 Nanoparticles

This work explores the structural, optical and dielectric properties and the magnetic behaviour of copper (Cu) (0-4%)-doped tin dioxide (SnO2) nanoparticles, synthesized by the sol-gel method using methanol as solvent. X-ray diffraction (XRD) analysis confirmed the tetragonal structure of SnO2. The inclusion of Cu in the SnO2 lattice enhanced the crystallite size of the Cu-doped SnO2 nanoparticles, as determined by the Scherrer method, and crystallite sizes were found to be consistent with the Williamson-Hall method. The morphology, observed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), revealed the formation of uniformly distributed nanoparticles of spherical shape. The formation of a characteristic peak in the range of 480-750 cm(-1) was associated with an antisymmetric O-Sn-O bridge functional group of SnO2. The reduced band gap is in accordance with the quantum confinement effect in synthesized samples. Strain-influenced dielectric studies conducted at room temperature within a frequency range of 1 Hz to 7 MHz revealed a relatively high dielectric constant, AC conductivity and low dielectric loss. Here, for the first time, electric modulus formalism is adapted to analyse the relaxation mechanism in Cu-doped SnO2 nanoparticles. The relaxation peak shift towards lower frequency (approximate to 1kHz)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \approx 1\;{\hbox{kHz}}) $$\end{document} in the investigated samples indicates the short-range mobility of ions and longer relaxation times. The transition from a diamagnetic to a paramagnetic state is confirmed by the addition of Cu content in the SnO2 lattice. The observed paramagnetism of the Cu-doped SnO2 nanoparticles is correlated with lattice strain. Cu doping led to an increase in magnetic moment on the order of 10(-1) emu/g. The synthesized samples with high dielectric constant, low dielectric loss and paramagnetic behaviour are found to be efficient candidates for high-frequency devices and biomedical applications. The longer relaxation times may make them suitable for future memory materials.