Microstructure and frequency sensitive electrical conductivity in Fe 3 BO 6 :B 2 O 3 of a hybrid vitroceramic nanocomposite

Iron oxyborate Fe 3 BO 6 , a mixed compound of iron oxide Fe 2 O 3 and iron borate FeBO 3 , offers multifunctional properties for electrodes, gas sensors, drugs delivery, or biological probes. To accolade useful properties, in this paper we report frequency ( f ) dependence of ac electrical conductivity ( σ ac ) of Fe 3 BO 6 , which is crystallized in shapes of thin plates (40–50 nm thickness) and rectangular bars (50–100 nm thickness) from an iron borate glass 40Fe 2 O 3 –60B 2 O 3 . Residual B 2 O 3 (10–15 wt%), which remains in a vitreous phase, forms a hybrid vitroceramic nanocomposite. This B 2 O 3 is useful to surface modify Fe 3 BO 6 so that it turns into a strongly correlated antiferromagnet with uncompensated surface Fe 3+ (3d 5 ) spins, showing only very small magnetization of the order of a few 10 −4  emu/g at room temperature. The σ ac ‐values measured at selective frequencies 0.1–10 3  kHz over a temperature range 300–575 K follow an activation energy varied from 0.345 to 0.244 eV, if the plot is analyzed in nearly linear parts, in raising frequency from 10 to 10 3  kHz. Primarily oxygen vacancies preside over a thermal assisted condition process wherein the initial σ ac ‐value increases effectively slowly against temperature. Otherwise, Fe 3 BO 6 with an optical bandgap 3.1 eV is a typical insulator. At f  ≥ 50 kHz, a characteristically weak peak arises in a spin‐reorientation transition near 433 K. The spin‐flops, which commence on a frequency assisted σ ac ‐value, illustrate the effect of a coupled system of the spins and charge carriers.