Plating of iridium for use as high purity electrodes in the assay of ultrapure copper

Fabrication of high-purity iridium electrodes using electrochemical deposition was performed to produce anodes used to assay ultrapure copper for extremely low uranium and thorium contamination primarily in support of the Majorana collaboration. High-purity iridium was deposited using a low current density under a constant voltage to produce a smooth film over a micron thick. The current efficiency was 23 % using an electrolyte of 40 mM IrCl3·4H2O, and H2SO4 employing polished iridium wires as electrodes at an elevated temperature of 80 °C. The electrodes can be converted to iridium oxide with different oxidation states by heating them in air for various periods.