[en] A solid-electrolytic ceramics on the basis of ZrO₂ with high strength and thermal resistance is fabricated. The ceramics is used for fabrication of sensitive elements in the form of capsule. A glass ceramics for pressure-tight connection of the ZrO₂ ceramics with a metal is developed. Different modifications of the transducers of the thermodynamic activity of oxygen are fabricated for different conditions. The transducer is certificated and approved for using in oxygen monitoring in a heavy coolant