Systematic analysis on the effect of sintering temperature for optimized performance of li<sub>0.15</sub>ni<sub>0.45</sub>zn<sub>0.4</sub>o<sub>2</sub>-gd<sub>0.2</sub>ce<sub>0.8</sub>o<sub>2</sub>-li<sub>2</sub>co<sub>3</sub>-na<sub>2</sub>co<sub>3</sub>-k<sub>2</sub>co<sub>3</sub> based 3d printed single-layer ceramic fuel cell – Projektit