Highly Porous Magnesium Silicide Honeycombs Prepared by Magnesium Vapor Annealing of Silica-Coated Polymer Honeycomb Films toward Ultralightweight Thermoelectric Materials

摘要

Magnesium silicide (Mg_(2)Si) is one of the few thermoelectric materials that is composed of high Clark number elements and exhibits an optimum temperature near 700 K. The advantage of Mg_(2)Si is that it is composed of universal elements and can be synthesized at low cost. However, it has the disadvantage of low efficiency in converting heat flow to electricity due to its high thermal conductivity. In this paper, Mg vapor annealing of silica-coated 1,2-polybutadiene honeycomb films enables the formation of a Mg_(2)Si honeycomb supported by amorphous carbon. The annealing temperature should be greater than 998 K to obtain Mg_(2)Si honeycombs, and we confirmed through detailed chemical analysis that a silica layer can be converted to a Mg_(2)Si layer via formation of Si. Furthermore, the honeycomb structure eventually reduced the thermal diffusivity even though only a single layer of the honeycomb structure formed on the surface. The obtained Mg_(2)Si honeycombs are good candidates for effective and low-cost thermoelectric materials for use in high-temperature applications.