Synthesis of KBiFe2O5 by electrospinning: Structural, optical, and magnetic properties

Ferroelectric oxides are currently being studied as absorbing materials in photovoltaic devices due to their spontaneous polarization that facilitates charge separation. KBiFe2O5 (KBFO) is a ferroelectric oxide with a perovskite like structure that has a low band gap; however, it has a relatively low electrical conductivity, which makes it difficult to transport and collect carriers. One way of overcoming that deficiency would be by decreasing the dimensions of the active layer. Thus, in this work, for the first time, nanofibers of KBFO were produced by electrospinning. Aqueous solutions of the ceramic precursors in the form of Fe, K and Bi nitrates were electrospun using poly (vinylpyrrolidone) (PVP) as the carrier. The as-spun fibers were calcinated at different temperatures and times. The pure KBFO phase was obtained after calcination at 750 °C, during 1.5 h at 15 °C/min; the nanofibers had diameters between 300 nm and 800 nm as analyzed by scanning electron microscopy (SEM). The interplanar distances of the (100) and (111‾) planes were 0.78 and 0.37 nm, respectively, as calculated by a VESTA software, x-ray diffraction (XRD) and transmission electron microscopy (TEM). Using a Magnetization-Field (MxH) curve, KBFO was found to be highly paramagnetic with low magnetization. The band gap was measured by spectrophotometry via a Tauc plot, resulting in a value of 1.72 eV. Therefore, KBFO in the form of nanofibers seems to have a high potential as an absorbing material in photovoltaic cells.