Investigation of thermal and magnetic behaviour of mixed valence iron hydroxyphosphate from Fe3(PO4)2(OH)2 lipscombite systems

Abstract Iron hydroxyphosphates are promising candidates for applications as cathode materials for Li-ion batteries, for example and present low production cost and reduced toxicity. In this work, a new fast method is proposed for the synthesis of mixed valence iron hydroxyphosphate from Fe 3 (PO 4 ) 2 (OH) 2 lipscombite systems. The as-obtained products were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, and magnetic measurements were carried out. Thermal treatment performed at 300 °C and 500 °C for 4 h indicate the formation of other lipscombite phases in accordance with thermogravimetric analysis where two weight loss steps were observed at ∼200 °C and ∼450 °C. A complex magnetic behaviour is observed with antiferromagnetic interactions at T N ∼140 K for the pristine lipscombite Fe 3 (PO 4 ) 2 (OH) 2 compound related to the strong magnetic interactions in the 3D crystal structure with small values for Fe-Fe distances and super-exchange contribution through PO 4 tetrahedra.