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 studied 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 equation of state of franklinite was investigated using the Birch-Murnaghan function, and the elastic properties thus inferred [K₀ = 166.4(± 3.0) GPa K′₀ = 9.3(± 0.6) K″₀ = -0.22 GPa^-1] are compared with earlier determinations for MgA1-spinel and magnetite. The structural behaviour of Zn-ferrite as a function of pressure was studied by Rietveld refinements, and interpreted in the light of a phase transition from spinel to either CaTi₂O₄- or MnFe₂O₄-like structure; this transformation occurs above 24 GPa.