Similar to LaCoO 4.14 , La 2−x Sr x CuO 4±δ shows oxygen diffusion at moderate temperatures. The Oxygen Isotope Back Exchange (OIBE) experiments are done in order to investigate the effect of strontium on the oxygen diffusion in as grown single crystals of La 2−x Sr x CuO 4±δ (x = 0, 0.05, 0.1, 0.15). Neutron diffraction data collected at TriCS@SINQ are in agreement with diffusion measurements achieved by oxygen back exchange. From 18 O/ 16 O isotope exchange between 40 °C to 1000 °C free oxygen mobility can be realized for x = 0, 0.05 below 500 °C but is depressed for x = 0.1 and 0.15. This gives evidence that low temperature oxygen mobility can be suppressed by replacing La with Sr. First crystal test using neutron single crystal diffraction proved the high quality of the samples.