Discovery of a New Boron-Rich Phase by Electron Crystallography

Abstract

In examining a supply of supposedly amorphous, highpurity, boron powder, a significant proportion of the particles were found to be well crystallized. Examination of these crystalline particles by convergent-beam electron diffraction revealed that they were orthorhombic with space group Pnma (a = 16.7, b = 17.7, c = 10.3 A,). Contaminating impurities are thought to be responsible for the formation of this crystal structure but the authors were unable to identify them by analytical transmission electron microscopy. Some remarkable electron diffraction effects resulted from the dense reciprocal lattice of Bragg reflection and these are described. Noncrystalline particles in the powder were, in fact, found to be quasicrystalline in nature with planar disorder.

Structural characterization of electrodeposited boron

“…The d-spacings and intensities were consistent with those of α-rhombohedral phase of boron, but the possibility of amorphous boron was not ruled out. Steeds and Wilson (1998) examined an amorphous boron sample and observed that a significant proportion of the particles were well crystallized in that sample. Examination of these crystalline particles by convergent beam electron diffraction technique revealed that they were orthorhombic with space group Pnma.…”