A first-principles study on the ferroelectric and optical properties of (Zn, Co)-doped barium titanate

In light of recent advancements in energy technology, there is an urgent need for lead-free BaTiO₃(BTO)-based materials that exhibit remarkable ferroelectric and photoelectric properties. Notwithstanding the considerable experimental advances, a theoretical understanding from the perspectives of electrons and atoms remains elusive. This study employs the generalized-gradient-approximation plane-wave pseudopotential method to investigate the structural, electronic, ferroelectric, and optical properties of (Zn, Co)-codoped BaTiO₃ (BZCT) using density functional theory. The objective is to ascertain the extent of performance enhancement and the underlying mechanism of (Zn, Co) co-doping in barium titanate. Our findings reveal that the incorporation of (Zn, Co) into the BaTiO₃ lattice significantly augments the tetragonality of the unit cell. Moreover, the ferroelectric properties are enhanced, with spontaneous polarization that is stronger than that observed in pure BTO, exhibiting excellent ferroelectricity. This characteristic improves the charge storage capacity of energy storage devices, providing critical performance support for applications such as high-energy-density capacitors. The results of the Hubbard+U algorithm indicate that the band gap of BZCT is reduced. Concurrently, the enhanced ferroelectric polarization increases the built-in electric field of the material, facilitating the separation of photogenerated carriers and improving optical absorption. The synergistic effect of narrowing the bandgap and enhancing carrier separation efficiency endows BZCT with practical application potential in visible-light-driven photocatalysis and ferroelectric photovoltaic devices. Consequently, BZCT materials represent promising candidates for energy storage and photovoltaic applications.