Abstract: A solid-state oxygen microsensor measuring the potential difference (EMF) generated across two electrodes deposited on a solid oxygen ion conducting electrolyte and located in a constant temperature gradient in the same ambient atmosphere is provided. An output voltage of the sensor is proportional to the corresponding temperature gradient established across the electrodes and the oxygen partial pressure of the ambient atmosphere at such time. The solid-state oxygen microsensor is useful in the application of combustion systems, for example, to maintain and improve combustion efficiency levels and reduce undesirable emissions within the exhaust.