A Chimie Douce Route to Pure Iridium Oxide

Pure iridium oxide has been synthesized through a chimie douce process. This synthesis proceeds by a slow basic hydrolysis of hydrated iridium(III) chloride, at room temperature. A highly disordered oxihydroxide IrO1.45(OH)1.10·1.5H2O is first obtained. It has been characterized by thermal analysis, particle-induced X-ray emission (PIXE), X-ray diffraction, and X-ray absorption at the iridium LIII edge. Unlike commercial iridium oxide powders, this phase is entirely free of chlorine. Calcination at 900 °C for 12 h leads to a well-crystallized iridium oxide, with the expected rutile-type structure (P42/mnm symmetry, a = b = 4.4990(2) Å, c = 3.1533(2) Å).