- © 2000 Mineralogical Society of America
PRESSURE CELLS FOR X-RAY DIFFRACTION
The development of apparatus to maintain materials at high hydrostatic pressure has been an active area of research for many years. From the pioneering work of Bridgman, during the early part of this century (Bridgman 1971), until the late 1960s, massive hydraulicly driven Bridgman-anvil and piston-cylinder devices dominated high-pressure science. Although there were later improvements in design, such as multi-anvil devices, it was not until the advent of the gasketed diamond-anvil cell, in the mid 1960s, that high-pressure studies were possible in non-specialized laboratories. Diamond has remarkable properties; not only is it the hardest known material it is also highly transparent to many ranges of electromagnetic radiation. Indeed incorporating these attributes, the gasketed diamond-anvil cell has become the standard tool for the generation of high pressures over the last three decades and has been applied in a wide range of experimental studies such as Brillouin scattering (Whitfield et al. 1976), Raman spectroscopy (Sharma 1977, Sherman 1984), NMR measurements (Lee et al. 1987) and, of course X-ray diffraction. It is this utility across a large range of science through physics, earth science and lately the life sciences that makes the development of the diamond-anvil cell as significant a revolution for measurement under non-ambient conditions in the physical sciences as that of the invention of the transistor to the whole sphere of electronics and computation.
As with all successful designs, the principles upon which the gasketed diamond-anvil cell (Van Valkenburg 1964) operates are elegantly simple (Fig. 1). The sample is placed in a pressure chamber created between the flat parallel faces (culets) of two opposed diamond anvils and the hole penetrating a hardened metal foil (= the gasket). A pressure calibrant is placed beside the sample and the free volume within …