Enhanced visible-light absorption and room-temperature ferromagnetism of [KNbO 3 ] 1- x [BaFe 1/2 Nb 1/2 O 3-δ ] x solid solutions

In this work, [KNbO 3 ] 1- x [BaFe 1/2 Nb 1/2 O 3- δ ] x (KBNFO) solid solutions were synthesized with sol–gel method. Structural, morphological, optical, and magnetic properties of KBNFO samples were investigated. X-ray diffraction spectra show that the incorporation of Ba 2+ and Fe 3+ ions in KNbO 3 lattice caused the orthorhombic to cubic phase transition of KNbO 3 . Despite the structural phase change, Raman results revealed the existence of long-range polar order in KBNFO solid solutions, indicating possible ferroelectric properties of KBNFO. Enhanced visible-light absorption and narrowed bandgap evaluated from Tauc plot were obtained in KBNFO samples. A minimum 2.41 eV bandgap was achieved for x = 0.4 sample. Ultraviolet photoelectron spectrum study showed that the enhanced visible-light absorption was mainly caused by the lowered conduction band. The samples also showed significant ferromagnetic behavior at room temperature. Their remnant magnetization increased with dopant concentration. Ferromagnetic behavior of KBNFO could be explained with bound magnetic polaron theory. The enhanced visible-light absorption and room-temperature ferromagnetism may indicate that KBNFO materials are of potential in photovoltaic and photoelectric applications.