New low-frequency relaxation process in La2CuO4+delta by internal frictionexperiments

The low-frequency relaxation internal friction spectrum of La2CuO4+delta wa s been measured from -170 to 200 degrees C in an automatic torsion apparatu s at frequencies between 0.1 and 5.0 Hz. Three new relaxation processes are found with maxima, which are attributed to thermally activated diffusive j umps of oxygen atoms or vacancies in the oxygen sublattice, according to va rious activation enthalpies of three experimental runs. It is shown that th e content of oxygen defect have important influences on the physical proper ties of La2CuO4+delta.