High-Pressure Synthesis and Superconductivity of the Laves Phase Compound Ca(Al,Si)₂ Composed of Truncated Tetrahedral Cages Ca@(Al,Si)₁₂

Abstract

The Zintl compound CaAl₂Si₂ peritectically decomposes to a new ternary cubic Laves phase Ca­(Al,Si)₂ and an Al–Si eutectic at temperatures above 750 °C under a pressure of 13 GPa. The ternary Laves phase compound can also be prepared as solid solutions Ca­(Al_1–<i>x</i>Si_<i>x</i>)₂ (0.35 ≤ <i>x</i> ≤ 0.75) directly from the ternary mixtures under high-pressure and high-temperature conditions. The cubic Laves phase structure can be regarded as a type of clathrate compound composed of face-sharing truncated tetrahedral cages with Ca atoms at the center, Ca@(Al,Si)₁₂. The compound with a stoichiometric composition CaAlSi exhibits superconductivity with a transition temperature of 2.6 K. This is the first superconducting Laves phase compound composed solely of commonly found elements