Investigating the impact of calcination temperature on the structural and optical properties of chromium-substituted Mg–Co ferrite nanoparticles

Abstract

The primary objective of this study is to comprehensively examine how the calcination temperature affects the structural, infrared, and optical properties of Mg0.6Co0.4FeCrO4 compounds. These compounds were synthesized using the sol-gel method and subjected to calcination at two distinct temperatures, namely 900 °C and 1100 °C. The X-ray diffraction measurements confirmed that the compounds adopt a cubic crystal structure with a space group of Fd3¯m. Furthermore, the FTIR analysis of these compounds revealed the presence of an absorption band corresponding to the stretching vibration of the oxygen atom and metal ions within the tetrahedral site. As the calcination temperature increased, various properties showed notable changes. The crystallite size, determined using the Debye-Scherrer equation from the strongest diffraction peak, increased from 48 nm at 900 °C to 56 nm at 1100 °C for the compounds. Additionally, the direct optical band gap energy (Eg) decreased from 1.346 eV to 1.322 eV with the rise in calcination temperature from 900 °C to 1100 °C. Furthermore, the Urbach energy values decreased from 0.491 eV to 0.310 eV as the calcination temperature increased from 900 °C to 1100 °C. The compounds exhibited direct optical transitions as per the absorption coefficient (α) and Tauc's model. The study delved into the impact of calcination temperature on various optical properties. Specifically, the penetration depth, extinction coefficient, and refractive index were thoroughly investigated and their findings interpreted. In addition, the dispersion parameters were examined using the Wemple and DiDomenico single oscillator model and it was discovered that these parameters were significantly influenced by the calcination temperature. Moreover, as the calcination temperature increased, the optical dispersion moments (M−1 and M−3) exhibited a decrease. Finally, the study also explored and interpreted the influence of calcination temperature on the real and imaginary parts of the dielectric permittivity and conductivity of the compounds. These analyses provide valuable insights into how calcination temperature affects the optical characteristics of the studied compounds.