New Phases at High Pressure

Abstract

In spite of the considerable amount of work by Bridgman and co-workers on both applied and fundamental research in high-pressure physics from 1915 to 1945, the use of high pressure for the synthesis of new materials was more or less neglected by chemists. Perhaps because of the relative complexity of high-pressure equipment, they paid more attention to the role of high temperatures for the preparation of new phases. In the period from 1945 to 1955 geologists began to use high-pressure, high-temperature conditions in order to synthesize minerals encountered in volcanic rock whose origin was the deeper portions of the earth’s mantle (100–400 km). Only after 1955, the date of the announcement of the synthesis of diamond by the General Electric Co., did the advantages of using high-pressure conditions for the synthesis of new materials become evident to chemists. At that time many laboratories developed high-pressure facilities and chemists started to investigate pressure-temperature phase diagrams of the elements—more than forty years after the first synthesis of black phosphorus.(1,2) In several years a large number of new, denser phases of the elements were discovered. Some of the high-pressure phases had physical properties quite different from those of the ambient-pressure phases, e.g., high-pressure phases of silicon and germanium with the white tin structure were metallic and Bi II and III were both superconductors at low temperatures.