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Thermal evolution of structures and conductivity of Pr-substituted BaZr0.7Ce0.2Y0.1O3−δ: potential cathode components for protonic ceramic fuel cells
- Source :
- Repositório Científico de Acesso Aberto de Portugal, Repositório Científico de Acesso Aberto de Portugal (RCAAP), instacron:RCAAP
- Publication Year :
- 2018
- Publisher :
- Royal Society of Chemistry (RSC), 2018.
-
Abstract
- A complete solid solution forms between the perovskite proton conductor BaZr0.7Ce0.2Y0.1O3-δ (BZCY72) and BaPr0.9Y0.1O3-δ (BPY) on synthesis by the Pechini method and high-temperature annealing. Phase fields of selected members of the Ba(Zr0.7Ce0.2)1-(x/0.9)PrxY0.1O3-δ series were studied as a function of composition and temperature by high-resolution neutron powder diffraction revealing symmetry changes in the sequence Pnma → Imma → → Pm3m. Higher symmetry is favoured for low Pr contents and high temperatures, as consideration of tolerance factor suggests. A volume contraction, ascribed to dehydration, is observed by synchrotron X-ray diffraction on heating in air for lower x. Magnetic measurements and structural data support the presence of Pr in the IV valence state on the perovskite B site. Thermogravimetric analysis in CO2 to ∼1253 K indicates better chemical stability for x ≤ 0.445, whereas decomposition occurred for higher x. Electrical conductivity increases by over two orders of magnitude in dry air at lower temperature from x = 0.225 to 0.675; total conductivity reaches a value of 0.4 S cm-1 at 1173 K for x = 0.675. The series exhibits electron-hole transport with a positive pO2 dependence which increases with temperature, consistent with participation of oxygen vacancies in charge compensation of the Y3+ acceptor dopant. The activation energy for thermally activated hole hopping in air in the range 523-773 K decreases from ∼1 eV for BZCY72 to ∼0.4 eV for x = 0.675. Conductivity is generally lower in humidified N2 and air (pH2O ≈ 0.023 atm) than the corresponding dry atmospheres, consistent with consumption of holes by less mobile protonic species; however for x ≤ 0.225 the lower concentration of electron holes concomitant with higher oxygen-vacancy content in N2 results in slightly higher conductivity in wet conditions due to hydration of vacancies. Fil: Heras Juaristi, Gemma. Instituto de Cerámica y Vidrio de Madrid; España Fil: Amador, Ulises. Universidad San Pablo Ceu; España Fil: Fuentes, Rodolfo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina Fil: Chinelatto, Adilson L.. Universidade Estadual de Ponta Grossa; Brasil Fil: Romero De Paz, Julio. Universidad Complutense de Madrid; España Fil: Ritter, Clemens. Institut Laue Langevin; Francia Fil: Fagg, Duncan P.. Universidade de Aveiro; Portugal Fil: Pérez Coll, Domingo. Instituto de Cerámica y Vidrio de Madrid; España Fil: Mather, Glenn C.. Instituto de Cerámica y Vidrio de Madrid; España
- Subjects :
- Thermogravimetric analysis
Materials science
XRD
Annealing (metallurgy)
Físico-Química, Ciencia de los Polímeros, Electroquímica
Analytical chemistry
02 engineering and technology
Activation energy
Conductivity
010402 general chemistry
01 natural sciences
Electrical resistivity and conductivity
General Materials Science
Proton conductor
Proton Conductors
EIS
Valence (chemistry)
Renewable Energy, Sustainability and the Environment
Ciencias Químicas
General Chemistry
021001 nanoscience & nanotechnology
0104 chemical sciences
Neutron Diffraction
0210 nano-technology
CIENCIAS NATURALES Y EXACTAS
Solid solution
Subjects
Details
- ISSN :
- 20507496 and 20507488
- Volume :
- 6
- Database :
- OpenAIRE
- Journal :
- Journal of Materials Chemistry A
- Accession number :
- edsair.doi.dedup.....fccdd8640e4433d0058b423ae05684fc