A review on fabrication, sensing mechanisms and performance of metal oxide gas sensors

Processes for developing layers onto a substrate as the active component of metal oxide gas sensors are presented and other promising alternatives as thermal spraying are also proposed. In order to understand the electrochemical mechanisms involved, the relationship between surface reactions and the electrical signal is presented as determined by the influence of three main factors: the receptor function, the transducer function and the approachability. Distinct aspects for each key-step are discussed with the aim of achieving a better comprehension of the overall system. Performances of the most operated metal oxides and target-gases in distinct application markets are also reviewed.