Structural and optical properties of Mg-doped BaTiO3 nanoparticles for optoelectronic applications

In this work, we investigated the structural and optical characteristics of Mg-doped Ba 1-x Mg x TiO 3 (x = 0.00, 0.005, 0.01, 0.02, 0.04, and 0.06) powders, synthesized via the sol–gel method. XRD analysis demonstrated that the Ba 1-x Mg x TiO 3 samples crystallize in a pure perovskite-type structure, indicating that the Mg 2+ ions are successfully incorporated into the BaTiO 3 (BT) lattice at low doping levels (x ≤ 0.06). Magnesium incorporation reduces tetragonality with increasing dopant concentration, indicating a phase transition toward a pseudo-cubic structure. This observation was further confirmed by Rietveld refinement. The crystallite size was estimated using the Debye-Scherrer equation. UV–visible spectroscopy revealed a gradual decrease in the optical band gap energy (E g ) from 3.228 to 3.080 eV, accompanied by an increase in the Urbach energy (E U ) from 0.115 eV to 0.153 eV, with increasing Mg concentration from 0 to 0.06. Additionally, fundamental optical parameters, including the linear refractive index (n), dielectric constants (ε 1 and ε 2 ), optical conductivity (σ opt ), and the static index (n 0 ), were determined and correlated with the varying Mg content (x). An analysis of the linear and non-linear (NLO) optical properties revealed that the NLO refractive index (n 2 ) and third-order NLO susceptibility (χ (3) ), estimated from empirical relations, increase with increasing Mg content. These results indicate that Ba 1-x Mg x TiO 3 ceramics are promising candidates for advanced optoelectronic applications.