Phase transformations in the Tc-H system under high pressure

Investigated is hydrogen solubility in technetium at T=300 deg C and Psub(Hsub(2))<=19 kbar, thermal stability and the structure of Tc-H solid solutions, as well as isotherm behaviour of technetium electroresistance at T<=350 deg C and Psub(Hsub(2))< or approximately 15kbar. Hydrogen content in the specimens were determined using their decomposition in metal and molecular hydrogen in pressurized volume. Given are compositions of Tc-H specimens, saturated with hydrogen at 300 deg C and different pressures. It is noted, that at 225 deg C distinct anomalies occur on the electroresistance isotherms, hysteresis being observed at P0 approximately equal to 2kbar. It proves, that phase isomorphic transition E1-E2 is a transition of the 1-st type. Given are phase T-Psub(Hsub(2)) diagram of the Tc-H system and the pressure dependence of hydrogen content in Tc at 300 deg C. It is shown, that the transition from E1-range to E2 range is accompanied by a hydrogen solubility increase from n approximately 0.55 to n approximately 0.75