Three-step sintering of constrained yttria stabilised zirconia layers and its effect on microstructure and gas permeance

Three-step sintering has been applied to constrained yttria (3 mol%) stabilised zirconia (YSZ) layers. The sintering schedules use a coarsening stage (step one) prior to reaching the peak temperature (step two). Once the peak temperature has been reached the temperature is lowered and an isothermal dwell takes place (step three). As the YSZ layers form part of a solid oxide fuel cell, and thus need to prevent the fuel and air from mixing, gas flow across the layers was measured and gas permeance values calculated. Several of the three-step sintering schedules produced layers with lower gas permeance values compared with a conventional sintering schedule that is used currently. Further, a three-step schedule produced one of the lowest gas flow rates and minimised the maximum temperature exposure thus offering several potential benefits in terms of processing options.