Preparation of YSZ/YDC and YSZ/GDC composite electrolytes by the tape casting and sol-gel dip-drawing coating method for low-temperature SOFC

The composite electrolytes for low-temperature solid oxide fuel cells were fabricated via coating the YSZ sol on tape-casted substrates of yttria doped ceria (YDC) and gadolinia doped ceria (GDC). The doped ceria substrates with 98% of relative density were prepared by the tape-casting method followed by the sintering at 1,500°C for 2 hours. The YSZ polymeric sol for dip-drawing coating was synthesized by the partial hydrolysis of Zr-n-butoxide. The optimum dip-drawing coating rate for obtaining pinhole and crack free YSZ film was 2 cm/min using YSZ polymeric sol with 1.13 mol/ of concentration. After 10 times coating on ceria substrates with YSZ followed by the heat-treatment at 1,400°C for 2 hours, the fully densified YSZ film with 2.0 m of thickness without pores, cracks, or chemical reactions could be obtained. The results of single cell tests shows that YSZ layer coated doped ceria composite electrolyte prepared by the sol-gel dip-drawing method has an superior single cell performance to YSZ electrolyte without dissociation of ceria substrate.