A ZrO2-based solid-electrolyte ceramic was developed in the course of engineering sensors. This ceramic is characterized by high strength and thermal shock resistance. This ceramic was used to fabricate sensitive elements in the form of capsules. Sital was developed for an air-tight and strong ceramic-metal bond. Different modifications of sensors for the thermodynamic activity of oxygen for different conditions were designed and built. The sensor was certified by Gosstandart of Russia, entered into the State registry of means for performing measurements, and approved for application.