Abstract. Effect of 3 mol% of transition elements doped 8YSZ such as YSZZn, YSZFe, YSZCo and YSZMn on the ionic conductivity. SOFCs mostly operate at higher temperature. By substitute with dopants, it can reduce the operating temperature and costs. In this experiment, 3 mol% dopants mixed with 8YSZ and sintered at 1550 °C, hold for two hours. Crystal structure, microstructure, sintering behaviour and ionic conductivity at 300 o C were investigated. XRD demonstrates three phases (cubic, monoclinic and tetragonal) were obtained. It was confirmed that small additions of TMOs (Mn, Fe, Co and Zn) promotes densification, grain growth and ionic conductivity compared to pure 8YSZ. YSZZn obtained the highest ionic conductivity, 3.55 X 10 -3 mS cm -1 at 300 °C.