Due to such chemical processes occurring in non-stoichiometric iron oxide, the temperature dependence of the lattice parameter of rs-Fe 1-x Zn x O above 700 K has a rather complex character. In the 300-700 K range the V(T) dependence for the equilibrium composition Fe 0.9 Zn 0.1 O is practically linear, while for the metastable Fe 0.5 Zn 0.5 O solid solution it is apparently quadratic (Fig. ).