Structure and Moessbauer study of the double perovskite Ba2InCu1-xFexO4+y (x = 0.5)

The substitution of Fe for Cu stabilizes the structure of Ba2InCuO4+y and an order-to-disorder structural transformation is observed upon varying the preparation conditions. This variation occurs either by heating the ordered phase at higher temperature in air or by heating it in Ar atmosphere during thermogravimetry experiments. Moessbauer spectroscopy revealed that, for the ordered sample, Fe is probably in a distorted tetrahedral coordination and shares with Cu the middle plane. In the disordered sample, due to cation disorder, there are two more sites: one corresponding to Fe3+ and one to Fe4+. The picture that emerges from the Moessbauer data mimics the observed behavior of iron-substituted Cu(1) sites of the 123 compound