Composite electrodes for use in solid electrolyte devices

An oxygen ion-conducting solid electrolyte device characterized in that the solid electrolyte is impervious to gas and is selected from the group consisting of zirconia, hafnia, thoria, and ceria, doped or alloyed with one or more oxides selected from the group comprising calcia, magnesia, yttria, scandia and rare earth oxides, said solid electrolyte carrying at least one electrode which comprises a mixture of a minor proportion of a noble metal selected from the group consisting of platinum, silver, gold, palladium, iridium or rhodium and mixtures or alloys of any two or more of said metals, and a major proportion of a semiconducting metal oxide with either electronic n-type or hole p-type conductivity selected from the semiconducting oxides or complex oxides of one or more of the transition metals having atomic numbers 24-30, metals having atomic numbers 49-50 and the lanthanides having atomic numbers 57-71 wherein said noble metal is present in an amount from an amount effective to lower the time constant and the electrode resistance of said electrode as compared to either of said noble metal alone or said semiconducting metal oxide alone upto an amount of 40% by weight.