Thermal expansion behavior and microstructure in bulk nanocrystalline selenium by thermomechanical analysis

Thermal expansion behavior of bulk nanocrystalline (NC) Se samples with a g rain size range of 16-46 nm was studied by thermomechanical analysis (TMA) in the temperature range 290-373 K. Bulk NC Se samples were prepared by iso thermally crystallizing the as-quenched bulk amorphous solid at 373-478 K. The glass transition and crystallization of the remaining amorphous Se in t he partially crystallized samples were studied by TMA, and compared with th e results of differential scanning calorimetry (DSC). The glass transition temperature, as determined from the thermal expansion behavior, was 308 K, 11 K lower than the value by DSC analysis. A structural densification pheno menon was observed in a grain growth process of an as-crystallized NC Se sa mple by TMA. It was found that the linear thermal expansion coefficient of the bulk NC Se sample increased with a reduction of grain size, from which the deduced thermal expansion coefficient of the interface decreased with t he refinement of the grain size. (C) 1999 Elsevier Science S.A. All rights reserved.