Lattice distortion and strain induced crack formation in Y-doped BaZrO3

Abstract

Proton conducting ceramics are promising solid electrolytes for protonic ceramic fuel cells. However, the presence of cracks remains a challenge before successful commercialization of the proton ceramic devices. This study investigates the impact of internal strain and lattice distortion on the crack formation in BaZr_0.8Y_0.2O_3-δ. During sintering, pellets are covered with controlled amount of sacrificial powder 2 or 3 times of the pellet mass, and the effects of adding BaCO₃ in the sacrificial powder is studied. The pellets sintered with 2 times sacrificial powder remain intact when dried, yet 53 % show cracks after hydration in 0.03 atm water vapor pressure. All pellets fracture into pieces when sintered with additional BaCO₃ in sacrificial powder, in which 0.07 mol% excessive Ba is observed in the actual composition. These Ba excess pellets show larger lattice constant compared to those prepared under other conditions. Strain analysis indicates that 0.14 % to 0.15 % micro strain is observed in the batches with cracks. Raman spectra reveal higher degree of lattice distortion in the BO₆ octahedra in the cracked batches. The findings highlight the role of lattice distortion in internal strain, and crack formation. This work may contribute to the processing of solid electrolytes in protonic ceramic fuel cells.