Variable temperature pressure cell for polycrystalline x-ray studies down to 2 K—application to Bi

A variable pressure diamond anvil cell is described for operation at temperatures continuously variable from 300 down to 2 K and controllable within 10 mK. Polycrystalline x-ray data are collected from the pressure cavity by means of either (1) standard photographic techniques, (2) diffractometer measurements, or (3) energy dispersive diffractometry. The facility has been used to examine parts of the phase diagram of Bi. Results from this study indicate that the Bi-I and Bi-III structures are retained to low temperatures; however, there is no evidence to support a structural transition from Bi-V to Bi-VIII.