Thermal Conductivity Standard Reference Materials from 6to 280K:VI. NBS Sintered Tungsten,

摘要

Thermal conductivity,electrical resistivity, Lorenz ratio,and thermopower data are reported for two specimens of NBS sintered tungsten for temperatures from 6to 280K. Variability of this tungsten was studied by means of electrical resistivity and residual resistivity measurements on 39specimens. These data indicate a material variability of about plus or minus 10% in thermal conductivity at helium temperatures. Above 90K variation in thermal conductivity is only about plus or minus 1%. To reduce the uncertainty caused by specimen variation at low temperatures,characterization by residual electrical resistivity data is described. By this procedure the low temperature uncertainty is reduced to about plus or minus 3%. (Author)