Phase diagram for the mixture of helium isotopes, 3He and 4He. Pure liquid 4He enters into the superfluid phase at 2.17 K (left in the figure). The presence of 3He shifts the superfluid transition to lower temperatures. If the liquid has sufficiently 3He, a phase separation takes place at low temperatures. Near zero temperature the 4He-rich phase contains at most 6% of 3He (lower left corner). The other phase consists of essentially pure 3He (lower right corner). Also the latter phase enters superfluid state but at a much lower temperature, which is not visible in the figure.
Note that the figure and the numbers above correspond to
saturated vapor pressure, and are functions of pressure.
Back to helium page19.8.2003, Erkki Thuneberg, Email, Suomeksi