Low-cost of 8 mol% of yttria stabilized zirconia (8YSZ) grade 204NS-G granulated powder doped with single dopant namely Zn(NO3)2, Fe(NO3)3 and mixed dopants (Fe/Zn) at varying mol% content (less than 3 mol%) were studied systematically in order to explore the properties of solid electrolyte. At the beginning of research, the effect of sintering temperature, sintering holding time and pressing load on the sinterability of granulated 8YSZ powder were studied. All studied samples from granulated 8YSZ powder not completely densify (> 90 %) even though being sintered at 1700 °C, prolonged the holding sintering time (7 hours at 1550 °C) and compacted at high pressing load (3.5 Tonnes). Thus, the initial 8YSZ powder was milled to change its surface characteristic. Both powder (initial powder and milled powder) had been compacted and sintered. Research based on different sintering time and pressing load had been investigated and comparison between both 8YSZ powders had been studied. Milled 8YSZ samples were successfully densified (98.33 %) at sintering parameter of 1550 °C for 5 hours with pressing load of 0.5 Tonnes, which ultimately generate better total conductivity (3.655 x 10-6 S/cm). In order to improve the total conductivity and the densification of 8YSZ sample in this grade, the milled 8YSZ samples were doped with 1, 2 and 3 mol% of single dopants (Fe or Zn). Results demonstrated that both dopants greatly reduced the activation energy for densification as well as increase the relative density successfully. Among the single doped samples, 2 mol% Zn doped milled 8YSZ sample (YSZ-2Zn) resulted better total conductivity than 2 mol% Fe doped milled 8YSZ sample (YSZ-2Fe) which were 6.885 x 10-5 S/cm and 6.251 x 10-5 S/cm, respectively. Although densification in YSZ-2Fe (92.09 %) was slightly higher than YSZ-2Zn (90.49%) but the grain growth in iron doped sample affecting its total conductivity. Besides that, cubic phase of YSZ-2Fe (49 wt%) was slightly higher than YSZ-2Zn (47.4 wt%), however sample YSZ-2Fe caused decrement in total conductivity. This is believed that higher tetragonality of the tetragonal phase consists in sample YSZ-2Fe. Thus, zinc ion has capability to control the accelerated grain growth in 8YSZ sample during final sintering stage which is a decisive factor on total conductivity. Study on mixture of Fe₂O₃ and ZnO in milled 8YSZ powders revealed that sample YSZ-1.25Fe0.75Zn (Sample E), YSZ-1.75Fe0.25Zn (Sample G) and YSZ2.0Fe1.0Zn (Sample Y) possess the highest cubic-ZrO2 above 50 wt%, produced lower crystallite size (20nm to 25nm), pore-free morphology with relative density more than 90 % and achieved the highest total conductivity 2.473 x 10-5 S/cm, 2.578 x 10-5 S/cm and 7.398 x 10-6 S/cm, respectively as measured at 300 °C. Among the three samples, sample G (YSZ-1.75Fe0.25Zn) was considered as the best sample which possesses higher total ionic conductivity result. In short, mixed dopants (Fe/Zn) produce excellent ceramics which could contribute to solid electrolyte technology development.
