In Situ Formation Of Fepo4-Ii: A Neutron Diffraction Study

The structural transformation of FePO4 from the trigonal berlinite phase to the orthorhombic CrVO4 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 FePO4 structure was observed to form. This lowers the formation temperature required to promote this phase over the amorphous phase by similar to 100 K compared to previous reports. No other structured phases were observed during the formation process which implies that the CrVO4 structure is the most stable form at high pressures and is kinetically inhibited from forming at low temperatures.