Frequency-temperature dependent dynamics of dielectrics in ferric oxoborate Fe 3 BO 6 of cocktail structure of nanorods

Author: Kumari K.  

Publisher: Taylor & Francis Ltd

ISSN: 1362-3036

Source: Philosophical Magazine Letters, Vol.91, Iss.7, 2011-07, pp. : 498-509

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Abstract

Oxoborates have both dielectric and magnetic properties useful for magnetodielectric devices, sensors, or biological tools. Such compounds Fe2BO4, Fe3BO5, or Fe3BO6 are known to grow easily as single crystals in a liquid flux. A polycrystalline phase forms only on controlled conditions of a solid state reaction of the basic oxides. In this study, we report highly dielectric Fe3BO6 when grown in a specific shape of nanorods (∼200 nm diameter and 50-100 µm length) from an iron borate glass, which offers devisable shapes of sheets, discs, and fibers. Frequency (f)-temperature reliant dynamics of dielectric constant εr is studied over 25-300°C at 0.1-103 kHz frequencies. At low frequency such as 100 Hz, a large εr -value 40,000, better than most of high εr -value ferroelectrics, incurs at room temperature. At f ≥ 50 kHz, although only an order of diminished εr -value lasts, it increases steadily with temperature, possibly due to increasing electrical conductivity in a specific resistor-capacitor network. Suppressed dielectric relaxation and spin-flops share a merely weak spin-reorientation transition near 160°C. A stable power loss ≤0.5 lasts at f > 10 kHz useful for possible applications of magnetodielectric materials.