Effect of Microstructure and Composition on Ionic Conductivity of Rare‐Earth Oxide‐Doped Ceria

1998 ◽  
Vol 145 (2) ◽  
pp. 638-647 ◽  
Author(s):  
Seong Jae Hong ◽  
Karun Mehta ◽  
Anil V. Virkar
Keyword(s):  
Rare Earth ◽  
Ionic Conductivity ◽  
Rare Earth Oxide ◽  
Doped Ceria ◽  
Effect Of Microstructure

scholarly journals High Pressure X-ray Diffraction as a Tool for Designing Doped Ceria Thin Films Electrolytes

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 724
Author(s):  
Sara Massardo ◽  
Alessandro Cingolani ◽  
Cristina Artini
Keyword(s):  
Thin Films ◽  
High Pressure ◽  
Rare Earth ◽  
Ionic Conductivity ◽  
Bulk Material ◽  
Threshold Temperature ◽  
Doped Ceria ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rare Earth Doped

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.

Synthesis and Characterization of Zirconium Oxide Systems with Yttrium Rich Rare Earth Concentrate Additives

2014 ◽  
Vol 798-799 ◽  
pp. 174-181
Author(s):  
Paola Cristina Cajas ◽  
R. Muñoz ◽  
A.C. Rodríguez ◽  
J.E. Rodríguez-Páez ◽  
C.R.M. da Silva
Keyword(s):  
Rare Earth ◽  
Ionic Conductivity ◽  
Zirconium Oxide ◽  
Complex Impedance ◽  
Rare Earth Oxide ◽  
Precipitation Method ◽  
Oxide Systems ◽  
Electric Behavior ◽  
Controlled Precipitation

In this work, the yttrium rich rare earth concentrate (Re2(CO3)3) was used as additive aiming stabilization of cubic an tetragonal phases at commercial zirconium oxide with 3% mol of yttrium oxide. The use of high purity rare earth oxide as additive is being commercially used and this work aims to demonstrate the potential use of lower cost additives to produce solid electrolyte for oxygen sensors and fuel cell applications. The powders for the additive production were synthesized by the controlled precipitation method. After synthesis, the powders were de-agglomerated using mechanical grinding and mixed to commercial zirconia to produce the compositions ZrO2:3% Mol Y2O3:ƞ % Mol Re2O3 (ƞ=3,4,5,6), followed by uniaxial press and sintering at 1500 0C in two hours. The obtained sintered densities were above 96% of theoretical. X-Ray diffractometric analysis and Rietweld refinement demonstrated the stabilization of cubic and tetragonal phases for all samples with yttrium rich rare earth concentrate additives. Finally the electric behavior of the evaluated samples was carried out with complex impedance spectroscopy, showing conductivity improvement for samples with the chosen additive. At 500 0C the sample A-9% had a conductivity of 1,11E-3Ω-1.cm-1, well above of the sample without additive with conductivity 5,88E-4Ω1.cm-1, indicative that use of yttrium rich rare earth concentrate as additive increases considerably the ionic conductivity of comercial zirconium oxide. Key words: rare earth concentrate, controlled precipitation, ionic conductivity

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

2012 ◽  
Vol 209 ◽  
pp. 163-171 ◽  
Author(s):  
Jesús Prado-Gonjal ◽  
Rainer Schmidt ◽  
Jesús Espíndola-Canuto ◽  
P. Ramos-Alvarez ◽  
Emilio Morán
Keyword(s):  
Rare Earth ◽  
Ionic Conductivity ◽  
Doped Ceria ◽  
Rare Earth Doped

scholarly journals Hydrothermal Synthesis of Nanocrystalline ZrO2-8Y2O3-xLn2O3 Powders (Ln = La, Gd, Nd, Sm): Crystalline Structure, Thermal and Dielectric Properties

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7432
Author(s):  
Radu-Robert Piticescu ◽  
Anca Elena Slobozeanu ◽  
Sorina Nicoleta Valsan ◽  
Cristina Florentina Ciobota ◽  
Andreea-Nicoleta Ghita ◽  
...  
Keyword(s):  
Rare Earth ◽  
Hydrothermal Synthesis ◽  
Ionic Conductivity ◽  
Thermal Treatment ◽  
Ionic Conduction ◽  
Rare Earth Oxide ◽  
Large Temperature ◽  
Size Segregation ◽  
Co Doping ◽  
Co Doped

Zirconium dioxide (ZrO2) is one of the ceramic materials with high potential in many areas of modern technologies. ZrO2 doped with 8 wt.% (~4.5 mol%) Y2O3 is a commercial powder used for obtaining stabilized zirconia materials (8 wt.% YSZ) with high temperature resistance and good ionic conductivity. During recent years it was reported the co-doping with multiple rare earth elements has a significant influence on the thermal, mechanical and ionic conductivity of zirconia, due complex grain size segregation and enhanced oxygen vacancies mobility. Different methods have been proposed to synthesize these materials. Here, we present the hydrothermal synthesis of 8 wt.% (~4.5 mol%) YSZ co-doped with 4, 6 and 8 wt.% La2O3, Nd2O3, Sm2O3 and Gd2O3 respectively. The crystalline phases formed during their thermal treatment in a large temperature range were analyzed by X-ray diffraction. The evolution of phase composition vs. thermal treatment temperatures shows as a major trend the formation at temperatures >1000 °C of a cubic solid solutions enriched in the rare earth oxide used for co-doping as major phase. The first results on the thermal conductivities and impedance measurements on sintered pellets obtained from powders co-doped with 8 wt.% Y and 6% Ln (Ln = La, Nd, Sm and Gd) and the corresponding activation energies are presented and discussed. The lowest thermal conductivity was obtained for La co-doped 8 wt.% YSZ while the lowest activation energy for ionic conduction for Gd co-doped 8 wt.% YSZ materials.

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

Inorganics ◽  
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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