Effect of Temperature and Pressure on the Electrical Resistance of Four Alkaline Earth Metals

Abstract

The resistance of magnesium, calcium, strontium, and barium have been measured to 600 kbar at temperatures from 77 to 296\ifmmode^\circ\else\textdegree\fi{}K.Magnesium shows some shallow maxima and minima in resistance along an isotherm, but no striking features. Calcium has a phase transition at about 150 kbar to a semimetallic phase, and a second transition initiating near 300 kbar, to a metallic state. Strontium has a sharp maximum in resistance below 40 kbar. Near the maximum it may be a semimetal. There is then a phase transition to metallic phase.Barium exhibits a very sharp rise in resistance at 140 kbar at 296\ifmmode^\circ\else\textdegree\fi{}K (190 kbar at 197\ifmmode^\circ\else\textdegree\fi{}K). At 77\ifmmode^\circ\else\textdegree\fi{}K there is a transition at 240 kbar which is somewhat more sluggish. Isobars obtained on this high-pressure phase indicate a very sharp transition near 160\ifmmode^\circ\else\textdegree\fi{}K. The evidence indicates that barium is a liquid at high pressure above 160\ifmmode^\circ\else\textdegree\fi{}K.