Phase transition of synthetic zinc ferrite spinel (ZnFe2O4) at high pressure, from synchrotron X-ray powder diffraction

Synthetic Zn-ferrite (ideally ZnFe2O4; mineral name: franklinite) was studi ed up to 37 GPa, by X-ray powder diffraction at ESRF (Grenoble, France), on the ID9 beamline; high pressure was achieved by means of a DAC. The P-V eq uation of state of franklinite was investigated using the Birch-Murnaghan f unction, and the elastic properties thus inferred [K-0 = 166.4(+/-3.0) GPa K'(0) = 9.3(+/-0.6) K " (0) = -0.22 GPa(-1)] are compared with earlier dete rminations for MgAl-spinel and magnetite. The structural behaviour of Zn-fe rrite as a function of pressure was studied by Rietveld refinements, and in terpreted in the light of a phase transition from spinel to either CaTi2O4- or MnFe2O4-like structure; this transformation occurs above 24 GPa.