Structural transformations in iron borate under high-temperature annealing

Scanning electron microscopy and X-ray diffractometry are used to study surface morphology and crystal structure of iron borate FeBO$_3$ annealed at different temperatures. Temperature limits of the structural stability are determined. It is shown that recrystallization to iron orthoborate Fe$_{3}$BO$_{6}$ and hematite $\alpha$-Fe$_2$O$_3$ takes places at temperatures of 800–900$^\circ$C and above 900$^\circ$C, respectively.