Modified structure and optical band-gap in perovskite ferroelectric (1-x)KNbO₃-xBaCo_1/3Nb_2/3O₃ ceramics

In the process of exploring ideal ferroelectric perovskites for photovoltaic applications, a novel kind of ceramic (1-x)KNbO₃-xBaCo_1/3Nb_2/3O₃ (xKBCNO) has been synthesized using solid-state method. The phase transition, microstructure, optical and ferroelectric properties of the compounds were investigated in detail. X-ray diffraction and Raman scattering spectra analyses indicate that single phase ceramics have been formed with cubic perovskite structure in space group Pm3m. Obvious crystal lattice expansion can be found as x increases. A narrow band gap of 1.87 eV is observed at x = 0.75, which proves the dramatic effect of BaCo_1/3Nb_2/3O₃ (BCNO) addition on the energy band gap. Besides, the room-temperature ferroelectricity has been detected in KBCNO ceramics controlled by the BCNO doping content. These results lay a solid foundation on further exploring the phase transition, band gap engineering, and electric properties in perovskite oxides, and indicate potential applications in perovskite solar cells.