The figure shows the measured superfluid transition of 3He in aerogel. The transition temperature is lower than in pure 3He (dashed line), and depends on the density and properties of the aerogel. The measurements are from Porto and Parpia (triangles) , Sprague et al (boxes) , and Matsumoto et al (circles) . There is evidence of both A phase  and B phase [4,5]. Recently, both A and B phases have been observed in the same experiment .
The aerogel is very porous and occupies only 2% of the volume. Theoretically aerogel is considered as an impurity, which in the simplest approximation is distributed homogeneously, and thus analogous to impurities in superconducting metals.
Back to 3He page5.9.2000, Erkki Thuneberg, Email