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

Abstract

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 ($$ \approx 1\;{\hbox{kHz}}) $$ 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.