A type of carbon dioxide gas sensor, which is applicable in various elevated temperatures, has been successfully realized. The primary advantage of this sensor is the ability to apply refractory lanthanum oxysulfate-lithium carbonate solid solution as the detecting auxiliary electrode. The sensor element, including the auxiliary electrode is durable at elevated temperatures and the operating temperature can be varied (from 600 to 450degreesC). The sensor response becomes <2 min, showing enhanced characteristics compared to similar previously reported CO2 gas sensors, and follows the Nernst theoretical relationship. (C) 2004 The Electrochemical Society.