Akademik Veri Yönetim Sistemi
IV. BASKENT INTERNATIONAL CONFERENCE ON MULTIDISCIPLINARY STUDIES, Ankara, Türkiye, 4 - 06 Ağustos 2023, ss.59-60
In this study, the synthesis and characterization of stabilized Bi2O3 solid electrolyte systems, especially
for the intermediate–temperature Solid Oxide Fuel Cells (IT–SOFCs), were performed. It is well known
that the face–centered cubic structure of pure Bi2O3 crystal exhibits unusual oxygen ion conductivity.
However, the super–ion conductor in this phase is stable over a very narrow temperature range, and thus
it needs to be stabilized for SOFC candidacy. For the stability study, Ce–Ho–Tb rare earth elements
were used as dopants, and all compositions were synthesized by solid–state reactions at room
temperature. To obtain ideal phase–stable materials the produced samples were annelaed at 750 °C for
100 hour. Annealed samples were characterized by a series of experimental studies, including X–Ray
Diffraction (XRD), Thermogravimetry and Differential Thermal Analysis (TG and DTA), Four Point
Tip Method (FPPT), and Field Emission–Scanning Electron Microscope (FE–SEM). Among all
samples, the Ce–rich ones exhibited the highest values in electrical conductivity, especially at the 2:1:1
dopant content ratio. Here, it was observed that the cation polarizability had a serious effect on the
conductivity results. On the other hand, the XRD patterns clearly revealed that the diffraction peak of
the (111) plane shifted as the doping concentration increased, indicating that the partial cation exchange
was successful in the crystal lattice. The crystal phase transition (α→δ) was quite evident on the DTA curves of samples 4Ce4Ho4Tb and 4Ce4Ho8Tb. In this study, the highest electrical conductivity at 700
°C was obtained for sample 8Ce4Ho4Tb with 0.30 S/cm. FE–SEM images clearly indicated the
aggregation of atoms in Ce–rich samples. Besides, FE–SEM images of Tb–rich samples heavily
included surface holes predicted to cause doping–index conductivity decay.
Keywords: Phase transition, Solid oxide fuel cell, Lattice contraction, Microstrain, Grain size and
boundary.