1209.3822 (Qiaoming Wang et al.)

Nuclear quadrupole interactions of 111In/Cd solute atoms in a series of
rare-earth palladium alloys    [PDF]

Qiaoming Wang, Gary S. Collins

Nuclear quadrupole interactions were measured at 111In/Cd probe atoms in rare-earth palladium phases RPd3 having the L12 structure using the technique of perturbed angular correlation of gamma rays (PAC). Measurements were made for pairs of samples having Pd-poorer and Pd-richer boundary compositions of the RPd3 phase field, typically 75 and 78 at.% Pd. Two signals were detected, corresponding to probe atoms on cubic R- and non-cubic Pd-sublattices. Site preferences of In parent probe atoms were characterized by site-fractions on the R- and Pd-sublattices. For all Pd-richer samples, probes exclusively occupied the R-sublattice. For Pd-poorer alloys with R= Tb, Er, Yb, Lu, Y and Sc, probes exclusively occupied the Pd-sublattice. For Pd-poorer alloys with R= Ce, Pr, Nd, Sm and Eu, probes occupied both sublattices, with site fractions varying as a function of temperature. Jump frequencies of Cd daughter probes on the Pd-sublattice were determined from nuclear relaxation caused by fluctuating electric field gradients. Activation enthalpies for diffusional jumps were determined from temperature dependences and found to increase linearly with decreasing lattice parameter along the series Pr, Nd, Eu and Sm. Jump frequencies were very high in CePd3 but too low to be detectable in Tb, Er, Yb, Lu, Y and Sc palladides. A correlation between site preferences and jump frequencies was noted. This paper provides a complete account of the jump frequency measurements and comparisons with measurements in other series of L12 phases.

View original: http://arxiv.org/abs/1209.3822