LXXVII. The thermal expansion of aluminium at low temperatures as measured by an X-ray diffraction method

The accurate determination of lattice cell dimensions by means of x-ray diffraction methods has been applied to the measurement of thermal expansion at temperatures down to 20°K. In the first results, obtained with aluminium, the ultimate sensitivity in the determination of values of δa/a (where a is the lattice parameter) is estimated to be about 5×10−−6. The value of (a 110-a 20)/a 273 obtained is 0·613 × 10−−3. The results represent a tendency for the Grüneisen γ to increase at the lowest temperatures.