Electronic structure correction via DFT+U+mBJ, ferroelectricity, n-type half-metallicity, and high figure of merit in B/C/N/F-substituted BaTiO3

The various features of the pristine (prist.)/X = B/C/N/F@O-substituted (subst.) BaTiO${}_3$ (BTO) perovskite oxide are investigated through $ab$-$initio$ calculations. It is revealed that the prist. motif is a non-magnetic insulator keeping an bandgap ($E_g$) of 3.5 eV for GGA$+U+$mBJ, which is in 100% accordance with the experimental one and contains a spontaneous polarization (P) of 28 $\mu$Ccm⁻². It is found that the X-substitution has a negative influence on structural distortions, resulting in lower P. The most astonishing feature is that the F@O-subst. BaO-layer-based structure displays an $n$-type half-metallic (HM) character holding a giant $E_g$ of 3.3 eV in the spin-majority channel, which is large enough to prevent reverse leakage current and guarantee the HM state. Strikingly, a high figure of merit of 1.04/1.05 at 300 K makes the prist./F@O-subst. BaO-layer-based structure, valuable for designing the thermoelectric devices.