Nanocrystalline SrMnO3 perovskite prepared by sol-gel self-combustion method for sensor applications

Oxide compound with perovskite-type structure, SrMnO3, was investigated in view of its application as capacitive and/or resistive humidity sensor. The compound presents a porous structure with prevailing open tubular pores systems and it was obtained by sol-gel self-combustion method using polyvinyl alcohol as colloidal medium, followed by heat treatment. Air relative humidity (RH) has a big influence on sensor electric capacity. The best sensitivity as capacitive humidity sensor was found at working frequency of 40 Hz over a wide range of relative humidity (0-98% RH). At this frequency, within the interval 0-98% RH the capacity increases by 1200%, and the resistance decreases by only 18%. The sensor has a good linearity of the logCvs.RHcharacteristics. The sensor exhibits very small hysteresis, and a short response time. The investigated material holds promise for humidity monitoring applications, taking into account the low cost, a wide range of relative humidity and a low-contamination impact, as well as for the realization of some electronic components, which requires good stability of resistivity in the presence of environmental humidity factors.