  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 compositions of the Pd-poorer and Pd-rich
boundaries of the RPd3 phase fields, typically 75 and 78 at.% Pd. Two signals
were detected in most phases, corresponding to probe atoms on cubic R- and
non-cubic Pd-sublattices. Site preferences of parent In-probe atoms were
characterized by site-fractions of probes on the R- and Pd-sublattices. For all
Pd-rich samples, probes exclusively occupied the R-sublattice, consistent with
a heuristic rule that solute atoms tend to occupy the sublattice of an element
in which there is a deficiency. 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. In contrast, probes only
occupied the R-sublattice in Pd-poorer LaPd3. Jump frequencies on the
Pd-sublattice of daughter Cd-probes 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 as the lattice parameter decreases along the series Pr, Nd,
Eu and Sm. Jump frequencies are believed to have been even higher in CePd3 than
in PrPd3, but were too low to be detectable in Tb, Er, Yb, Lu, Y and Sc
palladides. A correlation between site preferences and jump frequencies is
noted and discussed. This paper provides a complete account of measurements of
jump frequencies of Cd-probe atoms and comparisons with similar measurements
made on other series of L12 phases.
