COMPRESSIBILITY THERMAL EXPANSION AND OTHER PROPERTIES OF HELIUM-3

Measurements of pressure versus temperature of solid He3 have been made for various constant volumes between 17.6 and 24.7 cm3/mole, in the temperature range from 0.35°K to the melting point. Use was made of a sensitive capacitive strain gauge, which is described. From the pressure, the compressibility and thermal expansion coefficient are obtained. By extending the isochores into the liquid region, these quantities are also obtained for the liquid at melting. The compressibilities of the solid and liquid in equilibrium at the melting curve are nearly equal. The expansion coefficient of the solid is positive in the range investigated. Comparison with specific heats and with other results is made, and values of the Grüneisen γ and Debye θ are obtained. A discontinuity in volume of about 0.1 cm3/mole at the bcc-hcp phase transition down to 0.35°K was found. © 1968 The American Physical Society.