Mössbauer Studies of Tin 119m Recoil Atoms in Some Mixed Oxides of Tin. I. The Nature of the Recoil Effects in Mg₂SnO₄

The Mössbauer spectrum emitted following thermal neutron irradiation of the spinel Mg 2 Sn 118 O 4 displays a subsidiary line which can be associated with Sn 119m recoil atoms at abnormal sites in the crystal. The isomer shift and (unresolved) quadrupole splitting of this line suggest that it originates from divalent tin ions in which there is an admixture of 5p‐electrons having predominantly p z ‐character. The temperature dependence of the Mössbauer fraction indicates a weak average binding which, according to the computed intensities of the quadrupole doublet, may result from a large 〈z 2 〉 along the principal axis of the electric field gradient. Isochronal and isothermal annealing data indicate that the defect line disappears irreversibly above 600 °C and that the annealing processes are distributed over a fairly narrow band of activation energies in the range 3 to 4 eV. These results are interpreted in terms of a defect complex comprising a divalent tin ion and an associated charge‐compensating oxygen vacancy.