Structural phase transition, impedance spectroscopy and narrow optical band Gap in 1-xKNbO3-xBaSc12Nb12O3

In the progress of exploring lead-free ferroelectric perovskites, a new solid solution of 1-xKNbO3-xBaSc12Nb12O3 is synthesized using solid state method. The effect of Ba and Sc codoping on structural phase transition, dielectric, ferroelectric, electrical, and optical properties is systematically studied. A narrow band gap of 1.98eV is observed at x = 0.05. On further increase in x, the optical band gap increases due to increased strain. The crystal symmetry changes from orthorhombic at x = 0.00 to tetragonal phase at x ≤ 0.15, remains in pseudocubic phase for 0.15 < x < 0.35, and finally transforms to the cubic symmetry at x ≥ 0.35. A new Raman active mode evolves at 180 cm-1 at x = 0.15, which could be the TO or LO phonon of A1 symmetry. The electrical microstructure of the prepared electroceramics at room temperature has been investigated using impedance spectroscopy. This newly synthesized ferroelectric perovskite material has promising potential applications for photocatalysis and photovoltaics, especially under the visible light spectrum.