Mechanical alloying of an immiscible α-${\mathrm{Fe}}_2$${\mathrm{O}}_3$-${\mathrm{SnO}}_2$ ceramic

A solid solution of about 6 mol % ${\mathrm{SnO}}_2$ in α-${\mathrm{Fe}}_2$${\mathrm{O}}_3$ has been prepared by mechanical alloying of α- ${\mathrm{Fe}}_2$${\mathrm{O}}_3$ and ${\mathrm{SnO}}_2$ powder blends. This result demonstrates that high energy ball milling can be used to prepare metastable oxide solid solutions with an extended range of compositions in the immiscible ceramic oxide system. X-ray diffraction and Mössbauer spectroscopy investigations show that mechanical milling of α-${\mathrm{Fe}}_2$${\mathrm{O}}_3$ amd ${\mathrm{SnO}}_2$ involves alloying on an atomic scale and that true solid solution formation occurs. We suggest that the high defect concentration and the chemical enthalpy of ${\mathrm{Fe}}^{3+}$-${\mathrm{O}}^{2\mathrm{-}}$-${\mathrm{Sn}}^{4+}$ interfaces between nanostructured α-${\mathrm{Fe}}_2$${\mathrm{O}}_3$ and ${\mathrm{SnO}}_2$ regions may serve as a driving force for the formation of a solid solution in the immiscible ceramic system.