Diffusional thermoelectric power in Al-Zn alloys during pre-precipitation

The diffusional thermoelectric power (DTP) has been evaluated for Al-Zn alloys which decompose through the formation of Guinier-Preston zones. The free-electron model, with isotropic as well as anisotropic relaxation times was used. The influences of the solute concentration, of the volume concentration of zones, and of the electronic mean free path on the DTP during pre-precipitation have been checked. In the isotropic case, in spite of the fact that this model reproduces the electrical resistivity anomaly which is observed experimentally, it is only under certain conditions and for GP zones of diameter less than the electronic mean free path that the DTP is reproduced. The anisotropic calculations show good qualitative agreement with experiment during the entire decomposition.