Effect of Sintering Aids on the Stress Evolution of Constrained Sintered Gadolinium-Doped Ceria Films

Abstract

The in situ stress evolution of constrained Ce0.9Gd0.1O1.95 (CGO) porous thick films containing no sintering aids, 3 mol% lithium, or 3 mol% cobalt were measured from 25-1040C in air. The addition of 3 mol% lithium facilitated relaxation of the 1040C constrained sintering stress, and raised the sintered film relative density from 59 ± 5% (for pure CGO) to 85 ± 5%. In contrast, the addition of 3 mol% cobalt did not facilitate relaxation of the 1040C constrained sintering stress, and only raised the sintered film relative density to 64 ± 5%. This is surprising because both lithium and cobalt at the 3 mol% doping level are effective unconstrained CGO sintering aids (reducing the sintering temperature from ~1400C to ~800C and ~1000C, respectively). These results are consistent with cobalt enhancing solid-state diffusion and lithium inducing liquid phase sintering. Anomalous, low-temperature tensile stresses were also observed for films of all three compositions.