Thermal conductivity of isotopically enriched 28Si:: revisited

The thermal conductivity of isotopically enriched Si-28 (enrichment better than 99.9%) was redetermined independently in three laboratories by high precision experiments on a total of four samples of different shape and degree of isotope enrichment in the range from 5 to 300 K with particular emphasis on the range near room temperature. The results obtained in the different laboratories are in good agreement with each other. They indicate that at room temperature the thermal conductivity of isotopically enriched 28 Si exceeds the thermal conductivity of Si with a natural, unmodified isotope mixture by 10 +/- 2%. This C Si reaches a maximum. finding is in disagreement with an earlier report by Ruf et al. At similar to26 K the thermal conductivity of 211 The maximum value depends on sample shape and the degree of isotope enrichment and exceeds the thermal conductivity of natural Si by a factor of similar to8 for a 99.982% Si-28 enriched sample. The thermal conductivity of Si with natural isotope composition is consistently found to be similar to3% lower than the values recommended in the literature. (C) 2004 Elsevier Ltd. All rights reserved.