Bandgap tuning of [KNbO3]1−x[BaCo1/2Nb1/2O3−δ]x ferroelectrics

Ferroelectric perovskite oxides [KNbO3]1−x[BaCo1/2Nb1/2O3−δ]x(KBCNO, δ>0 means the existence of oxygen vacancies) solid solutions (0.1≤x≤0.5)were successfully synthesized by doping Co and Ba into the lattice of KNbO3 though solid-state reaction. The band gap energy of KBCNO shifts down to 2.4 eV and became visible-light-active due to the doping affection on the energy band structure comparing with that of wide-band-gap semiconductor KNbO3 (3.4 eV). The X-ray diffraction and Raman spectra revealed that the KBCNO solid solutions are in perovsite phase and gradually transiting from orthorhombic to cubic structure with the different BaCo1/2Nb1/2O3−δ (BCNO) contents. The reduction of band gap value makes KBCNO ferroelectric a promising candidate for photovoltaic materials.