In this work, we investigate the impact of calcination temperature on the structural, elastic, and optical properties of Mg0.4Cd0.3Cu0.3FeCrO4 spinel ferrites aiming to optimize their performance for optoelectronic applications. Following synthesis via the sol–gel route, the samples were calcined at temperatures of 850 °C and 950 °C. X-ray diffraction (XRD) analysis with Rietveld refinement confirmed the formation of a single cubic spinel phase (space group \(Fd\overline{3}m\) ), with a marked increase in the unit cell parameters (from 8.324 Å to 8.327 Å) and crystallite size (from 78 nm to 91 nm by Scherrer method) when the calcination temperature increased from 850 °C to 950 °C. Concurrently, elastic parameters (force constants, stiffness constants, Young’s modulus, Debye temperature) increased significantly, indicating enhanced interatomic bonding and improved lattice stability. The calculated stiffness constants satisfy the Born stability criteria, and the Pugh coefficient (~ 1.66) reveals brittle but isotropic mechanical behavior (Poisson’s ratio ~ 0.25). Optically, increasing calcination temperature reduces the band gap energy (Eg) from 2.332 eV to 2.246 eV and the Urbach energy (Eu) from 0.569 eV to 0.252 eV, reflecting improved structural order and decreased defect density. Comprehensive optical analysis, including refractive index, penetration depth, extinction coefficient, dielectric constants, and nonlinear optical parameters, demonstrated the materiel has enhanced suitability for optoelectronic applications.
