Mechanochemical processing of IrO2–Ta2O5: An alternative route for synthesizing Ir and Ir(Ta)O2 solid solution

Abstract

This paper describes a study exploring milling and subsequent heat treatments of pure IrO2 and Ta2O5 powders. Reactants were milled under Ar atmosphere in a SPEX 8000D mill, with structural, morphological, and compositional characterizations (during milling and after subsequent heat treatments) by X-ray diffraction, energy-dispersive spectroscopy, and transmission electron microscopy. Electrochemical stability of powders was evaluated by open circuit potential (OCP). Results showed that the mechanical energy transferred during this process induces a reaction between IrO2 and Ta2O5, forming metallic Ir and Ir(Ta)O2 saturated solid solution. The study additionally shows that this reaction can be thermally induced with previous mechanical activation of reactants. Electrochemical evaluations of milled powders immersed in H2SO4 solution revealed that OCP shifts negatively with increasing milling time, approaching that of pure Ir at 15h milling.