Structural elucidation and iron oxidation states in situ formed β-Ca3(PO4)2/α-Fe2O3 composites

A detailed structural analysis on the in situ synthesized beta-Ca-3(PO4)(2)/alpha-Fe2O3 composites is demonstrated. Compositional ratios, the influence and occupancy of iron at the beta-Ca-3(PO4)(2) lattice, oxidation state of iron in the composites are derived from analytical techniques involving XRD, FT-IR, Raman, refinement of the powder X-ray diffraction and X-ray photoelectron spectroscopy. Iron exists in the Fe3+ state throughout the investigated systems and favors its occupancy at the Ca2+(5) site of beta-Ca-3(PO4)(2) until critical limit, and thereafter crystallizes as alpha-Fe2O3 at ambient conditions. Fe3+ occupancy at the beta-Ca-3(PO4)(2) lattice yields a Ca9Fe(PO4)(7) structure that is isostructural with its counterpart. A strong rise in the soft ferromagnetic behavior of beta-Ca-3(PO4)(2)/alpha-Fe2O3 composites is obvious that depends on the content of alpha-Fe2O3 in the composites. Overall, the diverse level of iron inclusions at the calcium phosphate system with a Ca/P ratio of 1.5 yields a structurally stable beta-Ca-3(PO4)(2)/alpha-Fe2O3 composites with assorted compositional ratios.