Comparison of jump frequencies of 111In/Cd tracer atoms in Sn3R and In3R phases having the L12 structure (R = rare-earth)

TL;DR

This study measures jump frequencies of 111In/Cd tracer atoms in rare-earth tri-stannides with L12 structure, revealing that diffusion mechanisms differ from indides and are influenced by vacancy types and phase composition.

Contribution

It provides new insights into diffusion mechanisms in Sn3R phases, showing that Sn-vacancies dominate diffusion, contrasting with indide phases where rare-earth or indium vacancies are key.

Findings

Jump frequencies are higher at In-rich boundaries in indides.

Jump frequencies are higher at Sn-poor boundaries in Sn-stannides.

Diffusion is controlled by different vacancies depending on the phase.

Abstract

Measurements were made of jump frequencies of 111In/Cd tracer atoms on the Sn-sublattice in rare-earth tri-stannides having the L12 crystal structure via perturbed angular correlation spectroscopy (PAC). Phases studied were Sn3R (R= La, Ce, Pr, Nd, Sm and Gd). Earlier measurements on isostructural rare-earth tri-indides showed that the dominant diffusion mechanism changed along that series. The dominant mechanism was determined by comparing jump frequencies measured at opposing phase boundary compositions (that is, more In-rich and more In-poor). Jump frequencies were observed to be greater at the In-rich boundary composition in light lanthanide indides and greater at the In-poor boundary composition in heavy-lanthanide indides. These observations were attributed to predominance of diffusion via rare-earth vacancies in the former case and indium vacancies in the latter. Contrary to results for the indides, jump frequencies found in the present work are greater for the Sn-poor boundary compositions of the stannides, signaling that diffusive jumps are controlled by Sn-vacancies. Possible origins of these differences in diffusion mechanisms are discussed.