Synergistic Suppression of Ionic Conduction and Lattice Thermal Conductivity Through Trigonally Coordinated [CuI 3 ] 2− Units and Zero‐Dimensionality in Cs 3 Cu 2 I 5

ABSTRACT Semiconductors with ultralow lattice thermal conductivity (κ L ) are promising for thermoelectric and thermal barrier applications. Superionic materials often exhibit ultralow κ L because of their weak chemical bonds and long‐range ion migration, but their practical use is limited by chemic