Thermal disorder in the Fe0.5TiSe2

The crystal structure of Fe0.5TiSe2 has been studied in-situ by means of X-ray diffraction technique using synchrotron radiation upon heating in the temperature range 20–1000 °C. It was found that the iron sublattice undergoes a second order transition at a temperature of about 420 °C without affecting the TiSe2 sublattice. This phase transition has been described using an order parameter, the behavior of which is close to that for a 2D model. It was established that this transition is not related to the first-order transition, associated with the extraction of metallic iron. •The crystal structure of the intercalation compound Fe0.5TiSe2 was studied in the temperature range 25–1000 С.•An order-disorder transition was revealed in the sublattice of the intercalated iron at a temperature of 420 C.•Transition is the transition of the second order and it is described by an order parameter typical for 2D materials.•Order-disorder transition in the Fe sublattice is not associated with the retrograde solubility of Fe in this material