Über ε-Mangandioxid

Abstract

Authors have investigated electrolytically deposited massive MnO₂. Its main constituent is ε-MnO2, with the hexagonal unit cell a₀ = 2,80 Å and c₀ = 4,45 Å. Positions and intensities of arcs on the fiber- and powder patterns are in accordance with the structure as described in the literature, viz. a hexagonal close packing of O^2- ions with Mn⁴⁺ distributed statistically over 50% of the octahedral interstices; space group C6/mmc-D⁴_6h. A diffuse equatorial reflection, which yields a very broad line d = 4,22 Å in the powder pattern, can be interpreted as the consequence of partial order in the Mn-distribution, viz. a strong anticorrelation between the occupation chances of the centres of octahedra sharing faces.
In the oriented aggregates deposited along the field and concentration gradients, the crystals occur as laths extended along an a-axis, so that there is a sharp texture with a as the texture axis. The smallest crystal dimension is along c.