Investigating the long-term heating and analyte exposure effects on tin oxide thick-film sensors

Semiconducting metal oxide (SMO) thick-film gas sensors have the potential for robust, stable, and sensitive long-term performance in a variety of sensing applications which gives them an advantage over other gas sensing technologies. Understanding the long-term performance and operational effects on SMO thick-film sensors will play a large role in their future design and implementation. SRD developed and dedicated a test system for the test and measurement of 20 SMO thick-film sensors for extended durations. Each sensor tested was a tin oxide (SnO₂) nanoparticle thick-film deposited onto an alumina substrate along with an integrated platinum heater. Four gas-tight sensor chambers, each containing five SnO₂ sensors, were connected to a gas delivery system. Two chambers´ sensors were constantly operating at 300°C, while the other chambers´ sensors were heated to 300°C during weekly two-hour testing phases. For the remaining time, these sensors were unheated (ambient temperature). A constant 100sccm flow was maintained through all four chambers. The two-hour testing phase included the delivery of 5ppm and 100ppm nitric oxide (NO) to two out of the four chambers (one constantly heated and one intermittently heated), leaving the other two as controls.