Constrained sintering of Y2O3-stabilized ZrO2 electrolyte on anode substrate

Understanding the sintering processes extensively is critical in fabricating a flat cell for solid oxide fuel cell stacks, but few have reported the sintering process and stress development during the constrained sintering of the electrolyte layer on anode substrate. In this study, we show that the green tape of half cell fabricated by co-tape casting cracks into several pieces when it is heated directly to 1400 °C of profile I, while it remains flat and complete when the green tape is sintered with additional pre-sintered profile at 1300 °C of profile II. The strain rate characteristics indicate that the difference of 2.43 × 10−6 s−1 between the electrolyte and the anode layer leads to the stress development in the directly sintered cell, while it reduces to 6.7 × 10−8 s−1 for the pre-sintered cell, which is only 3% of that without pre-sintering. The stress based on continuum model calculated results in the sintered cell demonstrates that the stress increases from 0 at about 1000 °C to 2.60 MPa at 1300 °C, and increased from 2.60 MPa to 6.54 MPa in temperature range of 1300–1400 °C. But it was lower than half of the stress for the pre-sintered cell according to profile II. The SEM images, together with a circuit voltage of 2.22 V for two cell stack, indicate that the electrolyte of the unit cell is dense. The power is 41.7 W, with a power density of 0.26 W cm−2 at 1.4 V and 750 °C for a two tells stacks sintered according to profile II. The ASR of the two cells stack is 2.50 Ω cm2.

The stress of the cell sintered according to Profile I based on continuum model calculated results in that the stress increases from 0 at about 1000 °C to 2.60 MPa at 1300 °C, and increased from 2.60 MPa to 6.54 MPa in temperature range of 1300–1400 °C.Figure optionsDownload as PowerPoint slideHighlights
► A flat unit cell with dense electrolyte was obtained by sintering profile II.
► The stress evolutions based on continuum model were calculated.
► The power of two cells stack was 41.7 W at 1.4 V and 750 °C.