Influence of volatile organic compounds on the stability of resistive gas sensors

Abstract

W artykule przedstawiono wyniki badań stabilności długookresowej czujników grubowarstwowych. Stabilność badano w atmosferze lotnych związków organicznych (LZO). Na podstawie uzyskanych wyników można stwierdzić, że stabilność czujników w bardzo dużym stopniu zależy do masy cząsteczkowej LZO. Przeprowadzono próby regeneracji czujników zatrutych LZO. Wyniki badań pokazały, że regeneracja jest możliwa.In this paper there are presented the results of stability tests and the possibility of regeneration (after poisoning by volatile organic compounds – VOC) of thick-film gas sensors. The sensors were exposed to the atmosphere with a high concentration (1000 ppm) of VOC with a chain length of C6 to C12. The temperature stimulated conductance was measured. During the experiments the temperature was changed cyclically with rate 2 deg/sec. During the first increase in temperature the characteristic inflection in the dependence of conductance was observed due to the desorption of various components adsorbed on the surface of a gas sensitive material (Fig. 2). The results of experiments showed the high sensitivity of sensors in the atmosphere with VOC which was strongly dependent on the temperature (Fig. 3). However, the inactivation occurred rapidly in the presence of VOC with high molecular weight (Fig. 5a). The initial conductance gradually increased. Tests were also carried out to evaluate the possibility of temperature regeneration of sensors exposed to the atmosphere with a high concentration (1000 ppm) of VOC. For this reason after the exposition, the sensors were heated in the ambient atmosphere with cyclically changes of the temperature. The studies showed that after the first heating in the range from 150°C to 650°C the sensor parameters were close to the initial values (Fig. 5). Thus, sensors poisoned by VOC can be temperature regenerated in the atmospheric air