Porous tellurium oxide microtubes for room-temperature NO2 gas sensors

The sensing properties of porous TeO2 microtubes were observed from the electrical conductance change under NO2 gas at various concentrations and at room temperature. The sensors were fabricated by the thermal annealing of Te microtubes at 420 °C for 2 h in oxygen atmosphere. It was found that the sensitivity increased with NO2 concentration in the range 5-200 ppm and tended to saturate at higher concentrations. The response time decreased and the recovery time increased as gas concentration was raised, whereas at higher concentration the response and recovery times tended to constant values. The sensitivity, response and recovery times at 100 NO2 ppm were 75%, 100 s and 450 s, respectively. The sensors showed good stability and reproducible response throughout the test period.