AbstractThe temperature variation of the lattice constants of europium iron garnet (Eu3Fe5O12), europium sulphide (EuS) and europium fluoride (EuF2) has been studied using an X‐ray powder diffractometer. The lattice constant of Eu3Fe5O12 increases linearly upto 800 °C with an expansion coefficient of 10.4 × 10−6 °C−1. In the case of EuS, the lattice constant increases non‐linearly with temperature. At room temperature the expansion coefficient has a value of 14.3 × 10−6 °C−1. In EuF2 the lattice constant increases non‐linearly upto 140 °C. At higher temperatures, the lattice constant decreases with increasing temperature with a negative expansion coefficient of −29 × 10−6 °C−1 over the range 170–235 °C. The cause of the anomalous behaviour observed in EuF2 is yet to be understood.