Use of fcc Metals as Internal Temperature Standards in X-Ray Diffraction

A clear pattern of systematic error is found in thermal expansion values for Al, Ag, and Au commonly recommended and used as internal references for temperature determination in x-ray diffraction. Evidence comes from a critical analysis of the literature, including several studies of temperature measurement errors in powder cameras, and from new calibration of a thermometer used previously in precise lattice and length expansion studies. Necessary changes in the commonly accepted values for expansion of Pt and MgO are implied.