REORIENTATION OF THE CE-D PAIRS IN A PD95CE5DN ALLOY

Internal friction measurements have been carried out in a Pd95Ce5 allo y containing different amounts of D (0.003 <n(D)=D/(Pd+Ce)< 0.335) at vibration frequencies in the kHz range. Three IF peaks P-1, P-2 and P- 3 have been observed at around 160, 115 and 103 K, respectively. The h ighest temperature peak P-1 is due to D-dislocation interactions (Snoe k-Koester type of relaxation), the peak P-2 to stress-induced reorient ation of Ce-D pairs and the peak P-3 is due to stress-induced changes in the short-range order of D within the sublattice of the octahedral interstitial sites (Zener type of relaxation). The relaxation paramete rs of peak P-2 are: tau(O)(-1)=7X10(12)S(-1) and W=0.22 eV, while an e stimate of the anisotropy factor for the Ce-D pairs gives a value of 0 .038.