Diffusion welding of ZrO2 solid electrolyte cells

Zirconia based solid-electrolyte-cells can be applied as electrolysis-cells or fuel cells at high temperatures. Scaling up to technical aggregates must be realized by a gastight electrical series-connection of many tubular single cells. A suitable process for connecting single cells is diffusion welding. Starting materials were sintered zirconia-tubes (16 mm diameter, 10 mm length) and gastight interconnecting rings (16 mm diameter, 0.5-2mm length) from gold, platinum or electrically conducting mixed oxides. ZrO2-tubes and interconnecting rings were mounted in alternating sequence and diffusion welded under axial pressure at high temperatures. From economic reasons noble metals cannot be used for technical aggregates. The developments were therefore concentrated on the connection with mixed oxides. Optimized welding parameters are: 1400-15000C welding temperature, 2 hours welding time and an axial pressure of approximately 1 Nmm2. Up to now gastight tubes consisting of 20 single cells were preparated by diffusion-welding in one step. The process will be further developed for the production of 50-cell-tubes with a total length of about 60 cm. (orig.)