An investigation was made of phonon scattering by using the method of phonon spectroscopy and superconducting tunnelling junctions to examine nominally undoped or O-, Cr, Cu- and Fe-containing samples. A number of phonon scattering resonances were found at energies ranging from about 0.00025 and 0.003eV. Known resonances of Cr, between 0.0001 and 0.0007eV, were confirmed. Phonon scattering due to O, Cu, Fe and thermally induced defects was found. None of the observed phonon scattering resonances could be correlated with C or EL2 defects.

F.Maier, R.Eilenberger, W.Beck, K.Lassmann: Materials Science Forum, 1995, 196-201, 219-24