Carbon di:oxide sensor for continuous measurement in air for environmental control - based on galvanic cell with sodium ion conducting solid electrolytes contg. no carbonate and electrodes of precious metal

摘要

Porous precious metal structures (2, 3) are provided on both sides of a thin-walled solid electrolyte body (1). The body is made of a sodium zirconium phosphate modified with bivalent, trivalent or quadrivalent occurring elements e.g. the composition Na3MgZrP3O12, NaYZrP3O12 or Na3Zr2Si2PO12. Which for the precious metal form (2) of the CO2 sensitive electrode, is multi-times coated with a saturated sodium carbonate soln. and dried; sprinkled with fine sodium carbonate and covered with a porous body (6) of sodium carbonate. The metallic structure (3) belonging to the counter electrode (3) non sensitive to CO2 is coated with a paste. The paste consists of at least water and the mixture, resulting from a metal trioxide such as MoO3 or WO3, with an amount of sodium carbonate insufficient for the complete formation of the sodium salt, by mixing, calcination at 600-800 deg. C and redn. It is also covered with a porous body (7), made from the same dried mixture. This arrangement of a housing (12) of porous ceramic, facilitates entry of the measurement gas to both electrodes. The precious metal structures (2, 3) are connected with the precious metal conductors by the leads (4, 5). The galvanic cell is insulated, surrounded and held together by an electrical heating conductor (14). USE/ADVANTAGE - Industrial, horticultural, biotechnical and environmental purposes. Electrode compartments are separated gas tight from each other. Long term reference stability. CO2 readings not influenced by O2 vol. concns.