Hydrogen reduction of Cu-Mn-Fe-O spinel solid solutions

The crystal-chemical transformations accompanying the hydrogen reduction of CuxMn1-xFe2O4 (x = 0.2, 0.5, 0.8) solid solutions are investigated, and general equations describing these processes over the entire composition range (0 <= x <= 1) are derived. The results on the character of the processes involved differ radically from earlier findings. The equilibrium oxygen pressure is evaluated for the low-oxygen phase boundary of the spine] solid solutions throughout their stability region. For (MnFe2O4)(x1)(Cu0.5Fe2.5O4)(x2) (CuFe2O4)(1-x1-x2) solid solutions, which are of practical interest, the logP(O2) (1/T) data are well represented by the equation log (P-O2 /Pa) +/- 0.4 = 12.8 - 3.7(x1) - 2.8(x2) - 10280/T, which is of importance in controlled synthesis of single-phase materials in this system.