X-Ray Diffraction Studies at Low Temperatures

Abstract

Much current solid-state research, particularly that concerning the Fermi surfaces of metals and semimetals, demands knowledge of lattice parameters at temperatures in the liquid-helium range. A helium cryostat diffraction apparatus that has been in continuous use at these temperatures will be described, and some new research results from it are presented. The results include measurements of the lattice constants for gallium and for indium, of interest because the axial ratio influences both the nuclear electric quadrupole spectrum and also the cyclotron resonance. Previous measurements have disclosed unusual expansion characteristics but have not extended below liquid-nitrogen temperature. A second area in which the cryostat has been operating is the determination of the temperature of beginning recrystallization in high-purity metals that recrystallize at low temperatures. Experiments with zone-refined lead which has a recrystallization temperature near 160°K are reported.