Self-controlled growth of Fe3BO6 crystallites in shape of nanorods from iron-borate glass of small templates

Fe3BO6 can be an ideal compound for devising functional magnetic and dielectric properties in a single material for multiple applications such as electrodes, gas sensors, or medical tools. Useful to tailor such properties, here we report on a self-controlled Fe3BO6 growth in a specific shape of nanorods from a supercooled liquid precursor (an inorganic polymeric liquid or glass) of an initial composition (100 − x)B2O3 − xFe2O3, x = 40–50 mol%. B2O3 as a strong glass former co-bridges the Fe3+ ions in oxygen polygons primarily in a 2-D interconnected polymer network so that it dictates preferably a 1-D directional growth on the reaction Fe3+ species in form of a compound Fe3BO6, a favorable phase to nucleate and grow when annealing a precursor at 500–800 °C in ambient air. Distinct nanorods with a diameter ∼200 nm and 40–100 μm length have been formed on 10–15 min annealing a sample in microwave at moderate temperature 550 °C. A bonded surface B2O3 layer (15–25 nm thickness) has grown on the Fe3BO6 of the nanorods in situ in a specific structure. XPS bands in the Fe3+, B3+ and O2− species confer this model structure. A local BO3 → BO4 conversion has incurred in the boroxol (B3O4.5)n, n → ∞, rings in the surface layer, showing three distinct IR bands at 1035, 1215 and 1425 cm−1.

► Self-controlled growth of functional Fe3BO6 in shape of nanorods.
► Stable Fe3BO6 nanorods with a bonded surface layer.
► Microstructure in surface stabilized Fe3BO6 with boron oxide.
► XPS bands in surface stabilized Fe3BO6 of nanorods.
► Nucleation and growth of Fe3BO6 crystallites from an iron borate glass.