HIGHLY CONDUCTIVE V-DOPED d-Bi2O3 WITH 3×3×3 SUPERSTRUCTURE
Апстракт
Due to the increasing demands for new highly efficient and environmentally
friendly energy conversion technologies, the oxide ion conductors applicable in
solid oxide fuel cells (SOFCs) have widely been investigated. The high temperatureδ-Bi2O3 phase has been proposed as a good candidate for electrolyte in SOFCs
because it is the fastest known ionic conductor.
In this study, the possibility to stabilize O
2–
ion conductors related to the -Bi2O3
polymorph in Bi12VxO18+5x/2 (x = 0.5–1) system was investigated. Six starting
mixtures of α-Bi2O3 and V2O5 were dry homogenized in an agate mortar, heat
treated at 1000 °C for 1 h and then slowly furnace cooled. The samples were
characterized by XRD, TEM/SAED, optical microscopy, DTA and EIS techniques.
Based on XRD and TEM/SAED, if x ≥ 0.6 the high-temperature reaction
between α-Bi2O3 and V2O5 resulted in formation of microcrystalline single-phase
specimens containing the phase based on δ-Bi2O3. The obtained phases showed
main di...ffraction peaks corresponding to the cubic -Bi2O3 (space group Fm-3m and
a ≈ 5.6 Å). However, the detected weak reflections indicate that the true unit cell is
the 3×3×3 supercell with a ≈ 16.6 Å. An expected decrease of the unit cell
parameters with the dopant amount was found as the consequence of smaller dopant
ionic radius {ri(V5+) = 0.54 Ǻ and ri(Bi3+) = 1.03 Ǻ in the six-coordinated
environment [1]}. In the case of Bi12V0.5O19.25, traces of α-Bi2O3 were also found.
The XRD data of Bi12V0.7O19.75 were used for the Rietveld refinement giving
Bi102V6O168 as the composition of the 3×3×3 supercell. The octahedrally coordinated
V
5+ ions fully occupy 4a Wyckoff position, i.e. the corners and face centers of cubic
supercell, and partially occupy 32f. The Bi3+ ions are placed at the rest of 32f and at
24e and 48h with full occupation. At the 32f site, the cations are surrounded by five
oxide ions making a square pyramid. At the 24e site, the Bi3+ ions with four oxide
ions form a square pyramid with the cation at the apex. The coordination of Bi3+ at
the 48h is square planar.
Cyclic DTA curves showed that the following 3×3×3 → -Bi2O3 → -Bi2O3 →
Bi2O3(l) consecutive phase transitions occur on heating. On cooling, -Bi2O3
crystallizes from the melts and remains stable to about 530 °C. At this temperature,
an order-disorder transition takes place, i.e. -Bi2O3 → 3×3×3.
The sintered disk-shaped pellets were characterized by EIS at temperatures
between 760 and 820 °C. The sample with x = 0.6 demonstrates one of the highest
known conductivity among the published O2–
ion conductors, i.e. 0.66 S cm–1
at 760
°C with the lowest activation energy of 0.21(1) eV.
1. R. D. Shannon, Acta Cryst. A 32 (1976) 751
Кључне речи:
d-Bi2O3 / electrolyte / Solid oxide fuel cellsИзвор:
4th Conference of the Serbian Ceramic Society, 2017, 82-83Издавач:
- Društvo za keramičke materijale Srbije
Финансирање / пројекти:
- 0-3D наноструктуре за примену у електроници и обновљивим изворима енергије: синтеза, карактеризација и процесирање (RS-MESTD-Integrated and Interdisciplinary Research (IIR or III)-45007)
Институција/група
Institut za multidisciplinarna istraživanjaTY - CONF AU - Dapčević, Aleksandra AU - Dejan, Poleti AU - Radojković, Aleksandar AU - Branković, Goran PY - 2017 UR - http://rimsi.imsi.bg.ac.rs/handle/123456789/2868 AB - Due to the increasing demands for new highly efficient and environmentally friendly energy conversion technologies, the oxide ion conductors applicable in solid oxide fuel cells (SOFCs) have widely been investigated. The high temperatureδ-Bi2O3 phase has been proposed as a good candidate for electrolyte in SOFCs because it is the fastest known ionic conductor. In this study, the possibility to stabilize O 2– ion conductors related to the -Bi2O3 polymorph in Bi12VxO18+5x/2 (x = 0.5–1) system was investigated. Six starting mixtures of α-Bi2O3 and V2O5 were dry homogenized in an agate mortar, heat treated at 1000 °C for 1 h and then slowly furnace cooled. The samples were characterized by XRD, TEM/SAED, optical microscopy, DTA and EIS techniques. Based on XRD and TEM/SAED, if x ≥ 0.6 the high-temperature reaction between α-Bi2O3 and V2O5 resulted in formation of microcrystalline single-phase specimens containing the phase based on δ-Bi2O3. The obtained phases showed main diffraction peaks corresponding to the cubic -Bi2O3 (space group Fm-3m and a ≈ 5.6 Å). However, the detected weak reflections indicate that the true unit cell is the 3×3×3 supercell with a ≈ 16.6 Å. An expected decrease of the unit cell parameters with the dopant amount was found as the consequence of smaller dopant ionic radius {ri(V5+) = 0.54 Ǻ and ri(Bi3+) = 1.03 Ǻ in the six-coordinated environment [1]}. In the case of Bi12V0.5O19.25, traces of α-Bi2O3 were also found. The XRD data of Bi12V0.7O19.75 were used for the Rietveld refinement giving Bi102V6O168 as the composition of the 3×3×3 supercell. The octahedrally coordinated V 5+ ions fully occupy 4a Wyckoff position, i.e. the corners and face centers of cubic supercell, and partially occupy 32f. The Bi3+ ions are placed at the rest of 32f and at 24e and 48h with full occupation. At the 32f site, the cations are surrounded by five oxide ions making a square pyramid. At the 24e site, the Bi3+ ions with four oxide ions form a square pyramid with the cation at the apex. The coordination of Bi3+ at the 48h is square planar. Cyclic DTA curves showed that the following 3×3×3 → -Bi2O3 → -Bi2O3 → Bi2O3(l) consecutive phase transitions occur on heating. On cooling, -Bi2O3 crystallizes from the melts and remains stable to about 530 °C. At this temperature, an order-disorder transition takes place, i.e. -Bi2O3 → 3×3×3. The sintered disk-shaped pellets were characterized by EIS at temperatures between 760 and 820 °C. The sample with x = 0.6 demonstrates one of the highest known conductivity among the published O2– ion conductors, i.e. 0.66 S cm–1 at 760 °C with the lowest activation energy of 0.21(1) eV. 1. R. D. Shannon, Acta Cryst. A 32 (1976) 751 PB - Društvo za keramičke materijale Srbije C3 - 4th Conference of the Serbian Ceramic Society T1 - HIGHLY CONDUCTIVE V-DOPED d-Bi2O3 WITH 3×3×3 SUPERSTRUCTURE EP - 83 SP - 82 UR - https://hdl.handle.net/21.15107/rcub_rimsi_2868 ER -
@conference{ author = "Dapčević, Aleksandra and Dejan, Poleti and Radojković, Aleksandar and Branković, Goran", year = "2017", abstract = "Due to the increasing demands for new highly efficient and environmentally friendly energy conversion technologies, the oxide ion conductors applicable in solid oxide fuel cells (SOFCs) have widely been investigated. The high temperatureδ-Bi2O3 phase has been proposed as a good candidate for electrolyte in SOFCs because it is the fastest known ionic conductor. In this study, the possibility to stabilize O 2– ion conductors related to the -Bi2O3 polymorph in Bi12VxO18+5x/2 (x = 0.5–1) system was investigated. Six starting mixtures of α-Bi2O3 and V2O5 were dry homogenized in an agate mortar, heat treated at 1000 °C for 1 h and then slowly furnace cooled. The samples were characterized by XRD, TEM/SAED, optical microscopy, DTA and EIS techniques. Based on XRD and TEM/SAED, if x ≥ 0.6 the high-temperature reaction between α-Bi2O3 and V2O5 resulted in formation of microcrystalline single-phase specimens containing the phase based on δ-Bi2O3. The obtained phases showed main diffraction peaks corresponding to the cubic -Bi2O3 (space group Fm-3m and a ≈ 5.6 Å). However, the detected weak reflections indicate that the true unit cell is the 3×3×3 supercell with a ≈ 16.6 Å. An expected decrease of the unit cell parameters with the dopant amount was found as the consequence of smaller dopant ionic radius {ri(V5+) = 0.54 Ǻ and ri(Bi3+) = 1.03 Ǻ in the six-coordinated environment [1]}. In the case of Bi12V0.5O19.25, traces of α-Bi2O3 were also found. The XRD data of Bi12V0.7O19.75 were used for the Rietveld refinement giving Bi102V6O168 as the composition of the 3×3×3 supercell. The octahedrally coordinated V 5+ ions fully occupy 4a Wyckoff position, i.e. the corners and face centers of cubic supercell, and partially occupy 32f. The Bi3+ ions are placed at the rest of 32f and at 24e and 48h with full occupation. At the 32f site, the cations are surrounded by five oxide ions making a square pyramid. At the 24e site, the Bi3+ ions with four oxide ions form a square pyramid with the cation at the apex. The coordination of Bi3+ at the 48h is square planar. Cyclic DTA curves showed that the following 3×3×3 → -Bi2O3 → -Bi2O3 → Bi2O3(l) consecutive phase transitions occur on heating. On cooling, -Bi2O3 crystallizes from the melts and remains stable to about 530 °C. At this temperature, an order-disorder transition takes place, i.e. -Bi2O3 → 3×3×3. The sintered disk-shaped pellets were characterized by EIS at temperatures between 760 and 820 °C. The sample with x = 0.6 demonstrates one of the highest known conductivity among the published O2– ion conductors, i.e. 0.66 S cm–1 at 760 °C with the lowest activation energy of 0.21(1) eV. 1. R. D. Shannon, Acta Cryst. A 32 (1976) 751", publisher = "Društvo za keramičke materijale Srbije", journal = "4th Conference of the Serbian Ceramic Society", title = "HIGHLY CONDUCTIVE V-DOPED d-Bi2O3 WITH 3×3×3 SUPERSTRUCTURE", pages = "83-82", url = "https://hdl.handle.net/21.15107/rcub_rimsi_2868" }
Dapčević, A., Dejan, P., Radojković, A.,& Branković, G.. (2017). HIGHLY CONDUCTIVE V-DOPED d-Bi2O3 WITH 3×3×3 SUPERSTRUCTURE. in 4th Conference of the Serbian Ceramic Society Društvo za keramičke materijale Srbije., 82-83. https://hdl.handle.net/21.15107/rcub_rimsi_2868
Dapčević A, Dejan P, Radojković A, Branković G. HIGHLY CONDUCTIVE V-DOPED d-Bi2O3 WITH 3×3×3 SUPERSTRUCTURE. in 4th Conference of the Serbian Ceramic Society. 2017;:82-83. https://hdl.handle.net/21.15107/rcub_rimsi_2868 .
Dapčević, Aleksandra, Dejan, Poleti, Radojković, Aleksandar, Branković, Goran, "HIGHLY CONDUCTIVE V-DOPED d-Bi2O3 WITH 3×3×3 SUPERSTRUCTURE" in 4th Conference of the Serbian Ceramic Society (2017):82-83, https://hdl.handle.net/21.15107/rcub_rimsi_2868 .