Magnetite (Fe3O4) tetrakaidecahedral microcrystals: Synthesis, characterization, and micro-Raman study

► Fe(NO3)3∙ 9H2O was dissolved in the diethylene glycol by refluxing at 190 °C. ► Solutions were injected into quartz crucibles and placed in a tube furnace. ► Fe3O4 tetrakaidecahedra obtained by calcination at 800 °C in an N2 atmosphere. ► A clear direct phase transition from magnetite to hematite under laser irradiation.