Site-Selective Substitution in RT₂Zn₂₀: Effects of R-, T-, and Dual-Site Disorder

Intermetallic compounds with the general formula RT₂X₂₀ (R = rare-earth, T = transition metal, X = p-block element), known as “1-2-20 compounds,” exhibit unusual physical properties that make them promising for quantum computing, superconductivity, and thermoelectric applications. Most crystallize in the cubic CeCr₂Al₂₀-type structure, where rare-earth atoms occupy oversized atomic cages formed by cages. The structural flexibility of 1-2-20s allows a wide range of chemical substitutions at the R, T, and X sites, yet the effects of simultaneous substitutions—dual-site doping—remain largely unexplored. In this work, we synthesized and characterized three new 1-2-20 compounds: one with rare-earth site doping, one with transition-metal site doping, and one with dual-site doping. By comparing their structural stability, phonon scattering, and thermoelectric performance, we identify how individual substitution influences lattice dynamics and correlated properties. These results provide new insights into the structure–property relationships in 1-2-20 compounds, suggest strategies for optimizing thermoelectric efficiency, and establish a foundation for future dual-site doping studies.

The National High Magnetic Field Laboratory is supported by the National Science Foundation through NSF/DMR-2128556 and the State of Florida.