Li11Nd18Fe4O39-δ Revisited

The Mössbauer spectrum of Li11Nd18Fe4O39-δ (Chen et al, Inorg. Chem. 2012, 51, 8073) has been reinterpreted. The refined spectral parameters are similar to those observed for Nd18Li8Fe5O12 (Dutton et al, Inorg. Chem. 2008 47, 11212). The relative areas of the three components indicate that iron cations occupy the 2a, 8e, and 16i sites in disagreement with the iron occupancies of the 2a and 8e sites determined from neutron diffraction by Chen et al. The relationship between Li11Nd18Fe4O39-δ and Nd18Li8Fe5O12 is discussed and it seems quite possible that the sample prepared by Dutton et al is a kinetic product whereas the sample prepared by Chen et al. is the thermodynamically preferred product.