Abstract. The chemical composition of dense ceramics of erbia-stabilized 6-Bi203 was analyzed by Auger electron spectroscopy (AES) depth profiling using Ar + ion sputtering. The relative sensitivity factors (rsI) and sputter rates of bismuth and erbium in this material have been determined by electron probe microanalysis (EPMA) and chemical analysis. These results, supplemented by data from angle resolved X-ray photoelectron spectroscopy (ARXPS), shows a bismuth enrichment at the surface. Evidence has been found for reduction of the bismuth-oxide at the outermost part of the surface layer.Key words: AES, ceramic, sputtering, XPS.As discussed by Burggraaf and Winnubst [1] the chemical composition of grain boundaries and surfaces of ceramic materials controls sintering behaviour, grain growth and related properties such as fracture strength, toughness, wear resistance and also electrochemical and catalytic properties. Ceramic erbia stabilized 6-Bi203 may find commercial use in oxygen pumps, sensors and solid oxide fuel cells because of its high oxide ion conductivity. The aim of our research is to elucidate a possible segregation at the surface of this type of material.Auger electron spectroscopy (AES) can be applied for quantitative analysis of surfaces, provided that the relative sensitivity factors (rst) are known. The rsf values of the elements are known from literature [2] but often not applicable for composite materials, as for example shown by Keim and Aite [3] for silicon nitride. Experi-