Unique Materials and Properties in the New High Pressure-Temperature Regime above 250 Kbars,

摘要

(1) A new concept for generating static high pressures has resulted in the achievement of pressures exceeding 400 kbars with a sample volume of .015cc. Substitution of diamond for tungsten carbide anvils and multiple staging should increase the attainable pressures to near 1000 kbars. (2) The developed pressure system has been successfully coupled with a cryogenic capability to 10 K. (3) An ultrasonic measurement technique has been developed for use at high pressure which by measuring shear and longitudinal velocity,yields density as a function of pressure. Also, a dielectric system has been developed for detecting of transitions and measurement of density. (4) The P-T diagram for bismuth has been developed to 140 kbars with the discovery of two new phases,one of which may be superconducting to high temperature. (5) New electronic transitions at room temperature have been discovered in GaP (216 kbars),NaCl (290 kbars),and Bi VI-IX (320 kbars). In the latter,the resistivity is less than that of copper. (Author)