Thermal expansion of icosahedral Al-Pd-Mn and decagonal Al-Cu-Co quasicrystals

Thermal expansion measurements have been performed by X-ray diffractometry on icosahedral Al-Pd-Mn (i-(Al-Pd-Mn)) in the temperature range between 10 and 700 K and on decagonal Al-Cu-Co (d-(Al-Cu-Co)) in the range between 100 and 750 K. The linear thermal expansion coefficient alpha(T) of i-(Al-Pd-M n) is about half of that for the pure aluminium phase at room temperature a nd does not show a negative thermal expansion at low temperatures. The degr ee of anisotropy in the thermal expansion of d-(Al-Cu-Co) is small; the rat io of the average a between the tenfold periodic direction and a quasiperio dic direction perpendicular to it is 0.93 +/- 0.05. The Gruneisen parameter gamma(T) has been evaluated from the measured alpha(T). gamma for d-(Al-Cu -Co) is almost isotropic, similar to alpha. The gamma values for the two ph ases lie in the range between 1.5 and 1.8, which are comparable with those for conventional metallic crystals. They are almost constant over the tempe rature range studied.