Multi-scale architectured thermoelectric materials in the Mg2(Si,Sn) system

•We explore endogenous processing routes to produce novel architectured thermoelectric materials.•We create two distinct topologies and geometries at a nano/microscopic scale in Mg2(Si,Sn) alloys.•The first combines a nanograin microstructure with a large-scale periodic pattern in one direction.•The second is a layered structure in which the composition and microstructural scale vary in each layer.•The microstructural features are explained by the solidification path and the diffusion path followed.

Two different microstructural architectures featuring multiple length scales have been created in the thermoelectric Mg2(SixSn1−x) system. The first one combines the nano-grain microstructure, characteristic of rapid solidification, with a large-scale pseudo-periodic pattern in one direction. The second is a layered structure in which the composition and microstructural scale vary from layer to layer. The microstructural variability is obtained by two different processing methods, in the first from the consolidation of melt-spun Mg2(SixSn1−x) alloy and in the second the sequential thermal treatment of a diffusion couple between Mg2Si and Mg2Sn. In both cases the microstructural features are consistent with the predictions of the solidification and diffusion paths followed in each process.