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This review paper encompasses a study of metal-oxide and their composite based gas sensors used for the
detection of ammonia (NH3) gas. Metal-oxide has come into view as an encouraging choice in the gas sensor industry.
This review paper focuses on the ammonia sensing principle of the metal oxides. It also includes various approaches
adopted for increasing the gas sensitivity of metal-oxide sensors. Increasing the sensitivity of the ammonia gas sensor
includes size effects and doping by metal or other metal oxides which will change the microstructure and morphology of
the metal oxides. Different parameters that affect the performances like sensitivity, stability, and selectivity of gas sensors
are discussed in this paper. Performances of the most operated metal oxides with strengths and limitations in ammonia gas
sensing application are reviewed. The challenges for the development of high sensitive and selective ammonia gas sensor
are also discussed.
Effect of Water Vapor and Surface Morphology on the Low Temperature Response of Metal Oxide Semiconductor Gas Sensors