High-Temperature Ceramic Gas Sensors: A Review Sheikh Akbar,* Prabir Dutta, and Chonghoon Lee Center for Industrial Sensors and Measurements (CISM), Ohio State University, Columbus, Ohio 43210 Identifying chemical species and their quantification have become important in many industrial applications involving high temperatures and chemical contaminants. Center for Industrial Sensors and Measurements has developed TiO 2 semi- conducting sensors, zirconia and lithium phosphate-based electrochemical sensors, and a sensor array for high-temperature emission control. The underlying theme in our sensor development has been the use of materials science and chemistry to promote high-temperature performance with selectivity. This article presents key results of previous studies on CO, NO x , CO 2 , and O 2 sensors, and scope for future development. Introduction Intelligent systems based on sensors and controls can be used for health and safety (e.g., medical diag- nostics, air quality monitoring, and detection of toxic, flammable, and explosive gases), energy efficiency, and emission control in combustion processes, and indus- trial process control for improved productivity and product quality. There is a continuing need for the development of fast, sensitive, rugged, reliable, and low-cost sensors for applications in harsh industrial en- vironments found in heat treating, metal processing and casting, glass, ceramic, pulp and paper, automotive, aer- ospace, utility and power, chemical and petrochemical, and food-processing industries. Table I, for example, summarizes some of the key industrial applications of an oxygen gas sensor. 1–3 Similar data can be compiled for other sensors. The monitoring and control of combustion-related emissions are a top priority in many industries. The availability of reliable sensors along with predictive emission modeling tools would provide a better control of combustion, leading to reduction of toxic emissions and subsequent energy savings. According to a U.S. DOE report, 4 harsh environment sensors are predicted to save 0.25 quadrillion BTU/year of energy across all energy-consuming industries, identified as Industries of the Future (IOF). Sensors capable of providing three- dimensional maps of emission profiles will allow for feedback control systems of combustion processes, re- sulting in lower emissions and efficient use of fuels. Emissions-monitoring sensors for these applications include those for CO, NO x ,O 2 , CO 2 , hydrocarbons (HCs), and volatile organic compounds (VOCs). The control of combustion and emissions from glass tanks with the use of high-temperature sensors is a top priority of the glass industry. Emissions are the by- product of combustion, batching, fining, and melting Int. J. Appl. Ceram. Technol., 3 [4] 302–311 (2006) Ceramic Product Development and Commercialization This work was supported by CISM through the National Science Foundation contract no. EEC-9523358, the Department of Energy contract no. DE-FC26-03NT41615, and NASA-GMI contract no. NNC04AA48A. *Akbar@matsceng.ohio-state.edu r 2006 The American Ceramic Society