Electro-Sintering of Yttria-Stabilized Cubic Zirconia

Electro-sintering, i.e., electrically enhanced densification without the assistance of Joule heating, has been observed in 70% dense 8mol% Y2O3-stabilized ZrO2 ceramics at temperatures well below those for conventional sintering. Remarkably, full density can be obtained without grain growth under a wide range of conditions, including those standard for solid oxide fuel cell (SOFS) and solid oxide electrolysis cell (SOEC), such as 840 degrees C with 0.15A/cm2. Microstructure evidence and scaling analysis suggest that electro-sintering is aided by electro-migration of pores, made possible by surface flow of cations across the pore meeting lattice/grain-boundary counter flow of O2. This allows pore removal from the anode/air interface and densification at unprecedentedly low temperatures. Shrinkage cracking caused by electro-sintering of residual pores is envisioned as a potential damage mechanism in SOFC/SOEC 8YSZ membranes.