Thermal conductivity standard reference materials from 4 to 300 K. I. Armco iron: Including apparatus description and error analysis

Abstract

An apparatus for the measurement of thermal conductivity, electrical resistivity, and thermopower of solids from 4 to 300 K is described. This apparatus, a modified version of the one used earlier in thi s laboratory, utilizes th e steady-state, axial heat Aow method. Included is a de tailed di scussion of the limitations of the apparatus, probable errors, and data analysis methods.Thermal conductivity, electrical resistivity, Lorenz ratio, and thermopower data are reported for several specimens of Armco iron for temperatures from 4 to 300 K. At low temperatures the electrical resistivit y and thermal conductivity vary from specimen to specimen by more than 10 percent. However, the Lorenz ratios of these specimens differ by less than 2.5 percent; and the intrinsic resistivities calcu lated by using Matthiessen's rule differ by less than 0.5 percent of the total resistivities. Thus, Armco iron specimens can be used as standards by measuring the residual resistivities and utilizing the Lorenz ratio reported here.

Thermal conductivity, electrical resistivity, and thermopower of aerospace alloys from 4 to 300 K

“…The functions chosen to represent thermal conductivity, electrical resistivity, and thermopower are rather arbitrary, since adequate relationships based upon theoretical considerations are not available. These functional forms are given by eqs (1), (2), and (3) respectively: …”

“…significant figures retained in these parameters is dictated by the number of terms in eqs (1), (2), and (3), and only indirectly by the accuracy of the data. Values of thermal conductivity, electrical resistivity , absolute thermopower, and Lorenz ratio as computed from eqs (1), (2), and (3) are tabulated in tables 6 through 9 and illustrated in figures 2 through 7.…”

“…Values of thermal conductivity, electrical resistivity , absolute thermopower, and Lorenz ratio as computed from eqs (1), (2), and (3) are tabulated in tables 6 through 9 and illustrated in figures 2 through 7. The raw experimental data have be e n tabulated in an informal report for future referen ce.…”

“…A detailed error analysi s for the se measurements has been presented previously by Rust e t al. [2]. Based on this analysis of sys tematic and random .05 E c:…”

“…The reference block temperature is determined with a platinum resistance thermometer at temperatures above 10 K and from the vapor pressure of liquid helium near 4 K. The thermocouple calibrations are based on standard reference tables by Sparks, et al (NBS Monograph-in review) and small corrections to these tables based on spool calibrations at 4 K , 20 K, 78 K, and 273 K and in-place calibrations from 4 to 30 K. The platinum resistance thermometer was calibrated by NBS , Washington. Details of these calibrations are given by Hust et al [2]. The sample assembly is surrounded by a cylindrical temperaturecontrolled shield to reduce heat losses by conduction and radiation.…”