Abstract
In this paper the effect of zinc oxide (ZnO) addition on the phase transformation and ionic conductivity of 8 mol % Yttria-stabilised Zirconia (8YSZ) is investigated. Pure 8YSZ and ZnO doped YSZ ceramics are prepared using the solid state reaction method sintered at 1550°C for 2 hours. The X-ray Diffraction (XRD) results reveal the presence of tetragonal, cubic and monoclinic phase of Zirconium dioxide (ZrO 2 ) for all undoped and doped YSZ sintered samples. The phase stability of tetragonal YSZ was found to be increased with the increase in ZnO addition. Minor fraction of monoclinic phase was found in pure YSZ sintered sample and the amount of monoclinic phase decreased with the increasing amount of Zn after sintering at 1550°C for 2 hours. The fraction of cubic phase was also found to decrease with the increase in Zn concentration. The highest ionic conductivity of 1.03×10 −3 S cm −1 was obtained at room temperature for samples with 3 mol% ZnO. Pure 8YSZ sintered sample on the other hand, yielded 9.88x10 −4 S cm −1 .
Highlights
Solid oxide fuel cells (SOFCs) have attracted much attention in recent years due to their various potential advantages, including a wide variety of available fuels, inexpensive technology, good durability and highly efficient energy conversion [1,2,3]
Closed observation on the X-ray Diffraction (XRD) pattern revealed the presence of small fraction of monoclinic phase (ICSD 98-010-8439) phase which can be characterized by a peak at 2θ=28.2o
Yttria and zinc oxide (ZnO) based phase has not been detected which confirms the well incorporation of ZnO ions into the 8 mol % Yttria-stabilised Zirconia (8YSZ) matrix
Summary
Solid oxide fuel cells (SOFCs) have attracted much attention in recent years due to their various potential advantages, including a wide variety of available fuels, inexpensive technology, good durability and highly efficient energy conversion [1,2,3]. 8 mol% of Yttrium oxide (Y2O3) is one of the most explored compositions where the doping provides sufficient oxygen vacancies in fluorite ZrO2 lattice to ensure high ionic conductivity (σ) up to 0.1 S/cm It provide a stable cubic structure at 1000 ◦C as well as to obtain sufficiently high current densities and good power output.). Such high temperatures accelerate degradation of the fuel cell system and often lead to problems, such as solid reactions between the components, thermal degradation as well as thermal expansion mismatch. An increasing amount of dopants tends to form a second phase due to solubility limits, resulting in the reduction of conductivity
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