Pressure-Dependent Colossal Resistivity and Anomalous Optical Signatures in FeSbO4

FeSbO4exhibits an extraordinarily high electrical resistance of similar to 650 G Omega atpressures near 7 GPa at room temperature. Pressure-induced electrical transportmeasurements reveal a large resistance increase of 106compared to ambient pressure. Thisis the result of a very strong Coulomb repulsion between localized iron 3d-electrons caused byan abrupt shortening of the axial Fe(3d)/Sb(5s)-O(2p)Sigma-bonds in the Fe/SbO6octahedraas verified by in situ X-ray diffraction (XRD) study. Subsequent and concomitantstrengthening of Sb-O and weakening of Fe-O bonds drive FeSbO4into a Mott insulatingstate. Upon increasing pressure to 13 GPa, XRD and optical absorption spectroscopy furtherconfirm afirst-order phase transition from a tetragonal insulator with Fe3+in a high spin stateto an orthorhombic semiconductor with Fe3+in a low spin state without any metallization.Powder diffraction and transmission electron microscope images reveal that the recoveredsample after pressure release preserves the high-pressure orthorhombic structure albeit withFe3+in a high spin state and maintains its high resistance. The behavior at moderate pressuresmight be useful for potential applications in electronic switches, piezoresistive sensors, and other electronic devices.