Single crystals of lithium niobate (LiNbO3) withy‐cut orientation were irradiated at GANIL with 5.17 MeV/amu155Gd ions at a fluence ranging from 1.5×1011to 6.0×1011ions cm−2. After irradiation the samples were implanted with europium ions of 70 keV energy at a fixed fluence of 5×1016ions cm−2. Both irradiations and implantations were performed at room temperature. Thermal treatments in air, in the range 300–1100 °C, were applied to investigate the influence of the preirradiation damage on the thermal evolution of Eu implanted LiNbO3crystals. Transmission electron microscopy micrographs exhibit the amorphous track formed by high‐energy irradiations. Rutherford backscattering spectrometry results show that these amorphous tracks enhance the europium diffusion in depth of the LiNbO3. A diffusion coefficient and an activation energy were estimated to be about 4.2×10−15cm2 s−1and 0.42 eV, respectively. ©1995 American Institute of Physics.