The relationship between chemical composition distributions and specific grain boundary conductivity in Y-doped BaZrO₃ proton conductors

The relationship between chemical composition at a grain boundary and specific grain boundary conductivity is studied in Y-doped BaZrO₃ ceramics sintered at 1800 °C. Y enrichment at the grain boundary as yttrium concentration increased and Ba deficiency in ceramics as an increase of sintering time are observed. At the grain boundary, phase segregation, i.e. existence of secondary phase and amorphous phase which prevent proton migration, is not observed. The results indicate that at the grain boundary, concentration of Ba vacancy and Y substituted into Zr site is changed. Grain boundary conductivity shows significant dependences to Ba deficiency and Y concentration in ceramics. It is due to significant dependences of specific grain boundary conductivity to Ba deficiency and Y concentration in ceramics. The results indicate that proton migration across the grain boundary is sensitive to concentration of those effectively charged defect, i.e. Y substituted into Zr site and Ba vacancy at grain boundary.