Abstract: A method of evaporating an adherent metal electrode coating onto a surface of the zirconia exhaust gas oxygen sensor body. The zirconia is heated to an elevated temperature and the electrode metal evaporated onto the zirconia surface from an adjacent helix. The helix conforms to the zirconia surface and has electrode metal distributed throughout its length. After deposition at a rate of about 0.5-1.0 micrometers per minute is terminated, the zirconia is maintained at the elevated temperature for a few minutes and then slowly cooled for exposure to ambient conditions. Evaporation is from a conforming, closely spaced helix that also preheats the sensor body.

Abstract: A method of substantially increasing porosity and surface area on a zirconia body. The zirconia is etched with a mixture of concentrated hydrofluoric acid and concentrated sulfuric acid in a ratio effective to not only rapidly etch grain boundaries but to also rapidly pit individual zirconia grains. Concurrently the zirconia grains acquire a faceted or angular appearance. Etching is performed at 180.degree.-220.degree. C. for about 0.5-4 hours, along with ultrasonic agitation.