Studies of the chemical deintercalation reactions of iron-substituted lithium nickelate are extended here by evaluating in detail the structural changes induced by thermal treatment in a high-temperature diffraction camera. When pristine iron-substituted nickelate is heated above 700 degreesC, it transforms to a mixture of mixed oxide with the NaCl-structure, Li2O and O-2 are released. The thermal stability of the chemically deintercalated product is limited by the transformation to a spinel structure with the simultaneous release of oxygen. The final reduction to a rock-salt structure takes place at a lower temperature than in the pristine solid and without Li2O release.