Comparative Study of Zr/Te Co-Doped MgTiO

This study investigates the structural, electronic, and optical properties of pristine and Zr/Te co-doped MgTiO3 using first-principles calculations based on density functional theory (DFT). The calculations were performed within the full-potential linearized augmented plane wave (FP-LAPW) method implemented in the WIEN2k code. Structural optimization was carried out using the generalized gradient approximation (GGA), while the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential was employed to obtain improved electronic and optical properties. The optimized lattice parameter of pristine MgTiO3 was found to be a = 3.8427 Å. The calculated band gap of undoped MgTiO3 is 2.93 eV, confirming its wide-band-gap semiconducting nature with predominant ultraviolet absorption. Upon Zr and Te co-doping, the band gap significantly decreases to 1.15 eV for Mg8Ti7Zr1O23Te1 and further to 0.64 eV for Mg8Ti7Zr1O22Te2 due to dopant-induced electronic states near the Fermi level. Electronic structure analysis reveals strong hybridization between Te-p, O-p, Ti-d, and Zr-d orbitals, leading to band gap narrowing and a transition toward a direct band gap character. Optical calculations based on the complex dielectric function show a pronounced red shift of the absorption edge from the ultraviolet to the visible region, accompanied by an increase in the static dielectric constant and optical conductivity at low photon energies. These results demonstrate that Zr/Te co-doping effectively tunes the electronic structure and enhances visible-light absorption in MgTiO3, highlighting its potential for optoelectronic and energy-related applications.