Diffusion in La_nCoIn_3n+2 Phases Studied by Perturbed Angular Correlation

Abstract:

Jump frequencies of ¹¹¹In/Cd tracer atoms were measured for a series of layered phases La_nCoIn_3n+2 using the technique of perturbed angular correlation of gamma rays (PAC). The frequencies were determined by analysis of nuclear quadrupole relaxation produced by fluctuating electric field gradients. Samples were synthesized having nominal values n= 1, 2, 3, 5 and , with n= corresponding to the L1₂ phase LaIn₃. The phases form heuristically from LaIn₃ by replacing every (n+1)^th (100) mixed plane of La and In atoms with a plane of Co-atoms. For the n=1 phase, LaCoIn₅, jump frequencies were too small to detect. Two signals were observed, one for indium atoms next to the Co-planes and the other for more distant indium atoms. No relaxation was observed for atoms next to the Co-planes, indicating that there is no diffusion across the Co-planes. With increasing n, jump rates for the other In-atoms increased toward values observed for LaIn₃. Jump frequency activation enthalpies for n= 3 and 5 were observed to be the same as for n=, suggesting the same diffusion mechanism. However, the jump-frequency prefactors were found to be smaller for small n, which is attributed to reductions in the connectivity of the diffusion sublattice. We conclude that diffusion in the layered phases is remarkably similar to diffusion in LaIn₃ once the reduced connectivity is taken into account.

• Periodical: Defect and Diffusion Forum (Volumes 323-325)
• Pages: 453-458
• DOI: https://doi.org/10.4028/www.scientific.net/DDF.323-325.453
• Online since: April 2012
• Authors: Randal L. Newhouse, Gary Scott Collins
• Keywords: Atomic Jump Frequency, Diffusion, Hyperfine Interaction, Intermetallic Compound (IMC), Nuclear Quadrupole Interaction, PAC, Perturbed Angular Correlation (PAC)

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