131. The thermal conductivity of monoisotopic ionic crystals (sodium fluoride and cesium iodide) at low temperatures

✍ Scribed by Anna Foner-Cohen

• Publisher: Elsevier Science
• Year: 1958
• Weight: 66 KB
• Volume: 24
• Category: Article
• ISSN: 0031-8914
• DOI: 10.1016/s0031-8914(58)80646-1

✦ Synopsis

The thermal conductivity, K, of single crystals of NaF was measured at low temperatures. In the best crystal, Kmax was ~ 30 watts/cm-deg at a temperature Tmax 17°K. This crystal exhibited the exponential behavior expected at T ~ Tmax for crystals free of isotope scattering. In comparing K (from 3 ° to 30°K) of NaF crystals from different sources with nearly the same chemical purity it appears that strains and grown-in defects 1) are important factors limiting K. In the CsI, although the exponential behavior is observed at T ~ 11°K, at the lowest temperatures K appears to be limited by the large density of dislocations present in this plastic crystal. In CsI containing .2% T1 the impurity scattering as well as dislocations limit K. Upon thermal annealing of the T1 doped crystal K is increased somewhat, indicating partial annealing of dislocations.