Synthesis of La2−xNiO4+δ oxides by polymeric route: non-stoichoimetry control

The synthesis of La_2−xNiO_4+δ oxides has been done via a polymeric route. This method allows the preparation of a wide range of non-stoichoimetry values. Oxides with values as high as 0.25 have been synthesised. Correlations between processing parameters such as sol composition and heat treatment have been done with structural and microstructural properties of the oxides. In our synthesis conditions, the higher the mean grain size, the higher the non-stoichoimetry level.

Transmission electron microscopy on these oxides has shown that whatever the non-stoichoimetry level, the extra-oxygen arranges in the structure according to two superstructures which correspond to δ=0.25 and δ=0.17. This shows that our grains consist of a mixture of these compositions.