In situ formation of FePO4-II: a neutron diffraction study.

The structural transformation of FePO 4 from the trigonal berlinite phase to the orthorhombic CrVO 4 phase has been studied using neutron diffraction at high pressure and high-temperature. The berlinite structure was compressed to a pressure of 5.2(2) GPa and amorphisation observed. Upon annealing at temperatures above 798(28) K the high pressure FePO 4 structure was observed to form. This lowers the formation temperature required to promote this phase over the amorphous phase by ∼100 K compared to previous reports. No other structured phases were observed during the formation process which implies that the CrVO 4 structure is the most stable form at high pressures and is kinetically inhibited from forming at low temperatures. [ABSTRACT FROM AUTHOR]