Raman study on defect structure of high-temperature protonic conducting ceramics

Various acceptor-doped strontium cerates, Sr(Ce,M)O3−δ (M; dopant ions), were synthesized and treated under dry atmosphere. Each Raman spectrum was measured just after the dry treatment and compared with that of the as-sintered sample, focusing on the defect Raman band at 630 cm− 1. Relative intensity of the defect band, which increases monotonously with an increase in δ, increased by the dry treatment due to removal of water from lattice and resulting oxygen vacancy formation. Effect of dopant species on water solubility was discussed from relative intensity and peak center of the defect band.