Method for producing a sensor element for a potentiometric sensor, and sensor element

A method for manufacturing a sensor element for a potentiometric sensor, the method comprising:

• conditioning at least one region of a substrate consisting of copper, or of a copper-based alloy having a mass fraction of at least 60% copper, to produce an oxide layer comprising monovalent copper (Cu(I)) having a thickness of less than 5 μm, wherein the conditioning of the at least one region of the substrate is performed in a protective gas atmosphere, and wherein the protective gas atmosphere includes an inert gas or an oxygen-depleted atmosphere;
• and
• applying an ion-selective enamel layer at least to the at least one region of the substrate, including:
• applying an enamel preparation of an ion-selective glass to the at least one region of the substrate;
• and
• thermally treating the enamel preparation applied to the substrate to form the ion-selective enamel layer,
• wherein when the enamel layer is applied, a transition zone comprising copper(I) oxide is formed at an interface between the at least one region of the substrate and the enamel layer being formed, via which transition zone the at least one region of the substrate is in electrically conductive contact with the enamel layer, and
• wherein the thermal treatment of the enamel preparation is performed at least for a time at a temperature between 400° C. and 1085° C.