Evaluation of Low-Temperature Specific Heats and Thermal Conductivities of Er–Ag Alloys as Regenerator Materials

Abstract

The low-temperature specific heat for a series of Erx Ag100-x (x=40, 50, 60 and 70) alloys has been measured over the temperature range 1.6–30 K to evaluate their applicability as regenerator materials. In the temperature range 10–20 K, the volumetric specific heat for the x=50–70 samples exceeds that for Er3Ni, which is currently known as the most efficient regenerator material. The x=40 sample is superior to Er3Ni below 6 K. In addition, we found that the thermal conductivity for the present Er–Ag alloys is 5–10 times that for Er3Ni below 25 K. We conclude that the present Er–Ag alloys are suitable as regenerator materials, particularly if a composition-gradient composite regenerator material, in which the Er concentration varies from 70 to 40 along the direction of the gas flow, is fabricated.