CAPACITANCE EFFECTS AND GASEOUS ADSORPTION ON PURE AND DOPED POLYCRYSTALLINE TIN OXIDE

Conductance and capacitance effects have been studied simultaneously o n thin films and ceramics of tin oxide by using d.c. conductance and i mpedance measurements. Pure SnO2 and SnO2-CuO composite materials were studied. The total resistance of the samples is mainly due to the gra in boundaries and the adsorption on these boundaries of gaseous specie s with high dielectric constant as ethanol leads to a high capacitance value. This capacitance effect is more important in ceramics than in thin films. n-type SnO2-p-type CuO composite materials exhibit particu lar capacitance and conductance responses under pollutant gas, due to n-p junctions at the SnO2-CuO interfaces.