Diffusion of Mn-54 and Fe-59 in icosahedral single quasicrystals - Temperature and pressure dependence

Manganese self-diffusion and iron impurity diffusion have been investigated in icosahedral single quasicrystals of Al70.4Pd21.2Mn8.4 using the radiotracer method. The temperature dependences of Mn and Fe diffusion are described by the following activation enthalpies (Q) and pre-exponential factors (D-0): Mn-54: Q= 192.4 kJ mol(-1) (1.99 eV); D-0= 8.91 x 10(-4) m(2)s(-1), Fe-59: Q= 251.9 kJ mol(-1) (2.61 eV); D-0= 1.63 x 10(-2) m(2)s(-1). In addition experiments on the pressure dependence of (54)Nn diffusion were performed at 1023 K. An activation volume of 0.67 atomic volumes was obtained. The results are discussed with regard to the few literature data on quasicrystals and compared with diffusion in fee aluminium and in an iron aluminide. Very likely diffusion in Al-Pd-Mn quasicrystals occurs via a vacancy mechanism.