Quartz resonator with SnO2 thin film as acoustic gas-sensor for NH3

A quartz resonator with a thin SnO2 deposited film was investigated as a sensor for detecting the presence of ammonia in the ambient. The SnO2 film was used as a gas sensing element. Considerable variations of the resonance frequency Delta f=15 divided by 119 Hz were observed depending on the NH3 concentrations in the range of 10 divided by 5000 ppm. These variations were reversible at the conditions of the experiment carried out and no hysterisis was observed at these conditions. The mass Delta m of the adsorbed substance was calculated as a function-of the ammonia concentration c. The character of this dependence was well described with Delta m=2.4 c,(0.3) that is an equation based on the Freundlich isotherm adsorption model. Copyright (C) 1996 Elsevier Science Ltd