Аннотация:Spinels represent a class of ceramics with promising fundamental properties and a broad spectrum of industrialapplications. However, the knowledge of pressure effects on the crystal structure of spinel is limited, whichhinders their efficient synthesis using high-pressure techniques. In this paper, the effect of pressure on the crystalstructure of mixed spinel ferrite Fe0.8Ni1.8Sb0.4O4 was investigated at room temperature by in situ synchrotronbasedX-ray diffraction and Raman spectroscopy up to 42.19 GPa and 49.51 GPa, respectively. The X-raydiffraction results indicate that Fe0.8Ni1.8Sb0.4O4 adopts the cubic (spinel-type, space group Fd 3 m) structure atambient conditions, which undergoes a pressure-induced structural transition to a monoclinic phase (space groupP21/c), commencing at 20.83 GPa. This sluggish structural transformation turns out to be of the first-orderaccompanied by a volume collapse of about ~2.2 % when completed at 29.68 GPa. A second phase transitionto yet another metastable monoclinic structure with space group C2/m is observed to begin at 33.56 GPa.However, this phase transition does not complete even up to the highest pressure applied in the study. Ramanresults confirm that Fe0.8Ni1.8Sb0.4O4 undergoes a pressure-induced phase transition from Fd 3 m to P21/c at27.34 GPa. The observed phase transitions are reversible, and their mechanisms are discussed in the light of theRaman spectroscopy data. The present study deepens our understanding of the high-pressure behavior of spinels,which will facilitate their industrial syntheses and a better understanding of their role in planetary interiors.