Effect of co-doping with Mn and Nb on the properties of BaTiO₃

This study shows the effect of co-doping with manganese (Mn) and niobium (Nb) on the structural, morphological, optical, and ferroelectric properties of barium titanate (BaTiO₃). The precursor reagents used were barium carbonate (BaCO₃) and titanium dioxide (TiO₂), while manganese dioxide (MnO₂) and niobium pentoxide (Nb₂O₅) were added for doping at concentrations of 0, 1, 3, and 5 mol% in equal amounts. For the ceramic synthesis, the reagents in stoichiometric proportions are mixed, mechanically milled, compressed, and sintered at 1250°C. The physicochemical properties of the materials were analyzed using scanning electron microscopy (SEM/EDS), X-ray diffraction (XRD), micro-Raman spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, PFM analysis, dielectric, pyroelectric, and ferroelectric hysteresis loop measurements. The incorporation of dopants shows a decreasing trend in grain size, XRD and Raman spectra indicated that doped BaTiO₃ samples undergo a crystalline phase transition from the tetragonal phase to a pseudo-cubic phase, also the energy band gap decreased from 3.24 eV to 1.51 eV for undoped sample to 5% doped sample respectively. The ferroelectric hysteresis loops showed a trend of decreasing saturation and remnant polarization, and an increase in the coercive electric field (Ec). PFM analysis shows that the composition with 3 mol% of dopants presents a maximum in the piezoelectric coefficient d₃₃. The pyroelectric response follows a decreasing trend like remnant polarization. These results demonstrate that co-doping BaTiO₃ with Mn and Nb reduces its band gap energy, improving the absorption of a broader range of the solar spectrum, making it a promising ferroelectric material for photo response devices.