Engineering topics
Publications and source records attributed to Raag, Valvo.
Work at TECO has independently confirmed the early results obtained at JPL that high-temperature heat-treatment of SiGe/GaP alloys can significantly increase the figure of merit Z of these alloys. Several possible reasons for this improvement are given. Experiments are in progress to test these various hypothesis.
Annealing experiments in the temperature range 1100-1275 C have been performed on p-type Si(0.8)Ge(0.2) samples with BP, B(6.5)P, and GaSb material additives. Both electrical resistivity and Seebeck coefficient generally decrease for these samples as annealing temperature is increased, with thermoelectric power factor sometimes being improved by annealing.
The paper reports the results of measurements (Seebeck and Hall coefficients, electrical resistivity, and thermal conductivity) on silicon-germanium (Si-20 at. pct Ge) alloy with boron phosphide, B(6.5)P) as an additive, prepared as described by McLane et al. (1986). The power factor (Seebeck coefficient squared divided by electrical resistivity) and the thermal conductivity of SeGe/B(6.5)P material were found to be lower than for the 'standard' SiGe (Si-22 at. pct Ge) material. However, no net improvement was achieved in the figure-of-merit of the sample tested. It is suggested that structural inhomogeneities, revealed by a SEM examination, might be responsible for this lack of improvement.