The low-temperature thermopower of Frenkel defects in aluminium

The thermopower S has been measured in the temperature range 1.3-13K (reference: superconductor) on aluminium containing Frenkel defects (FD), i.e. self-interstitials and vacancies of equal concentration c (maximum 850 PPM). The FD have been produced in varying concentration and configuration by reactor irradiation at 15K ('isolated' FD) and subsequent annealing ('agglomerated' FD). A whole such cycle could be made on the same sample, and the measuring accuracy was very high. Applying the Nordheim-Gorter rule the authors obtained the specific coefficients of vacancies A V and interstitials A I . The 'phonon drag' coefficient B, however, was independent of the electron scattering anisotropy (further mod B mod decreased monotonically with c). This behaviour is unexpected from the Bailyn theory and obviously has to do with the exceptionally strong phonon scattering on the FD.