Temperature dependence of structure parameters in natural magnetite: single crystal X-ray studies from 126 to 773 K

Structural parameters and their thermal changes in natural magnetite, Fe₃O₄, have been studied using the single-crystal X-ray diffraction method in the temperature range 126-773 K. The cell dimensions, oxygen coordinate and atomic mean square displacements (m.s.d.'s) reversibly change as a function of temperature. The coordinate of oxygen remains almost constant at x = 0.2549 (1) below ~600 K, but increases with increasing temperature above this temperature. This characteristic behavior of the oxygen coordinate with temperature indicates that the cation disordering over the tetrahedral (A) and octahedral (B) cation sites occurs above 600 K. All atomic m.s.d.'s increase monotonously with temperature rise. The m.s.d.'s of the B atom show a unique temperature dependence. At lower temperatures the B atom prefers to vibrate along [111], but this preference is reduced with a temperature rise up to 630 K, above which the m.s.d. normal to [111] becomes dominant.

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