Increased ionic conductivity in microwave hydrothermally synthesized rare-earth doped ceria Ce1−xRExO2−(x/2)

Rare earth-doped ceria thin films are currently thoroughly studied to be used in miniaturized solid oxide cells, memristive devices and gas sensors. The employment in such different application fields derives from the most remarkable property of this material, namely ionic conductivity, occurring through the mobility of oxygen ions above a certain threshold temperature. This feature is in turn limited by the association of defects, which hinders the movement of ions through the lattice. In addition to these issues, ionic conductivity in thin films is dominated by the presence of the film/substrate interface, where a strain can arise as a consequence of lattice mismatch. A tensile strain, in particular, when not released through the occurrence of dislocations, enhances ionic conduction through the reduction of activation energy. Within this complex framework, high pressure X-ray diffraction investigations performed on the bulk material are of great help in estimating the bulk modulus of the material, and hence its compressibility, namely its tolerance toward the application of a compressive/tensile stress. In this review, an overview is given about the correlation between structure and transport properties in rare earth-doped ceria films, and the role of high pressure X-ray diffraction studies in the selection of the most proper compositions for the design of thin films.

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Revisiting ionic conductivity of rare earth doped ceria: Dependency on different factors

International Journal of Hydrogen Energy ◽

10.1016/j.ijhydene.2020.06.119 ◽

2020 ◽

Vol 45 (46) ◽

pp. 25139-25166 ◽

Cited By ~ 2

Author(s):

Sk. Anirban ◽

Abhigyan Dutta

Keyword(s):

Rare Earth ◽

Ionic Conductivity ◽

Doped Ceria ◽

Rare Earth Doped

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Effect of Reduced Atmosphere Sintering on Blocking Grain Boundaries in Rare-Earth Doped Ceria

Inorganics ◽

10.3390/inorganics9080063 ◽

2021 ◽

Vol 9 (8) ◽

pp. 63

Author(s):

Soumitra Sulekar ◽

Mehrad Mehr ◽

Ji Hyun Kim ◽

Juan Claudio Nino

Keyword(s):

Activation Energy ◽

Rare Earth ◽

Ionic Conductivity ◽

Grain Boundary ◽

Grain Boundaries ◽

Complex Impedance ◽

Doped Ceria ◽

Composite Electrodes ◽

Boundary Conductivity ◽

Rare Earth Doped

Rare-earth doped ceria materials are amongst the top choices for use in electrolytes and composite electrodes in intermediate temperature solid oxide fuel cells. Trivalent acceptor dopants such as gadolinium, which mediate the ionic conductivity in ceria by creating oxygen vacancies, have a tendency to segregate at grain boundaries and triple points. This leads to formation of ionically resistive blocking grain boundaries and necessitates high operating temperatures to overcome this barrier. In an effort to improve the grain boundary conductivity, we studied the effect of a modified sintering cycle, where 10 mol% gadolinia doped ceria was sintered under a reducing atmosphere and subsequently reoxidized. A detailed analysis of the complex impedance, conductivity, and activation energy values was performed. The analysis shows that for samples processed thus, the ionic conductivity improves when compared with conventionally processed samples sintered in air. Equivalent circuit fitting shows that this improvement in conductivity is mainly due to a drop in the grain boundary resistance. Based on comparison of activation energy values for the conventionally processed vs. reduced-reoxidized samples, this drop can be attributed to a diminished blocking effect of defect-associates at the grain boundaries

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