Analysis of the Electrical Complex Impedance Behavior of SnO2 Sensors

In this work the electrical complex impedance behavior of tin oxide thick films with the addition of Pd particles is analyzed. The films were obtained by the "Screen Printing" method. The conduction process is analyzed when the films are exposed to air having considered the existence of Schottky type potential barriers at the grain boundaries. The mean particle size was 250 nm and the film average thickness 400 microns. The palladium was added to increase the electrical sensitivity. Measurements were made in the range of temperature from 25 to 400°C. In this thermal range, barriers are affected by the process of gas intergranular diffusion that causes an increase of their height and, as consequence, an increase in the resistance. Also, the influence of the Pd addition on the conduction process is analyzed.