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Microstructure and frequency sensitive electrical conductivity in Fe 3 BO 6 :B 2 O 3 of a hybrid vitroceramic nanocomposite
Author(s) -
Kumari K.,
Bhargav K. K.,
Kumar N.,
Ram S.,
Kotnala R. K.
Publication year - 2011
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201026580
Subject(s) - materials science , analytical chemistry (journal) , microstructure , nanocomposite , band gap , antiferromagnetism , boron , electrical resistivity and conductivity , magnetization , conductivity , activation energy , condensed matter physics , nanotechnology , composite material , chemistry , optoelectronics , physics , chromatography , quantum mechanics , organic chemistry , engineering , magnetic field , electrical engineering
Abstract 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.