Phase transition in β-rhombohedral boron near 550 K

Differential scanning calorimetry (DSC) of high-purity, single crystal β-rhombohedral boron (melting point 2365 K) evidences a structural phase transition close to 550 K, which is obviously responsible for discontinuities of numerous physical properties in this temperature region. These can be consistently interpreted assuming site hopping of boron atoms between regular, partially occupied crystallographic sites in the crystal structure. This site hopping is influenced by optical excitation.

Peaks, indicating the phase transition near 550 K in β-rhombohedral boron, extracted from temperature-dependent cp measurements.Figure optionsDownload as PowerPoint slideHighlights
► Structural phase transition in β-rhombohedral boron.
► Site hopping of boron atoms.
► Experimental activation energy corresponds to theoretical generation energy of defects.
► The phase transition is modified by optical excitation.