Oxygen Ion Transport in Doped Ceria: Effect of Vacancy Trapping

2021 ◽  
Author(s):  
Mehmet Emin Kilic ◽  
Jong-Ho Lee ◽  
Kwang-Ryeol Lee
Keyword(s):  
Oxygen Vacancy ◽  
Ion Transport ◽  
Oxygen Diffusion ◽  
Oxygen Vacancies ◽  
Doped Ceria ◽  
Oxygen Ion ◽  
Vacancy Trapping ◽  
Ceo2 Lattice

Trivalent dopants in CeO2 lattice generate the oxygen vacancies in the lattice, that is vital to oxygen diffusion. However, the dopant also has two detrimental effects on the oxygen vacancy...

Electrical properties of ultrafine-grained yttria-stabilized zirconia ceramics

1997 ◽  
Vol 12 (9) ◽  
pp. 2374-2380 ◽  
Author(s):  
Shusheng Jiang ◽  
Walter A. Schulze ◽  
Vasantha R. W. Amarakoon ◽  
Gregory C. Stangle
Keyword(s):  
Grain Size ◽  
Oxygen Vacancy ◽  
Grain Boundary ◽  
Oxygen Vacancies ◽  
Synthesis Process ◽  
Physical Parameters ◽  
Fine Grained ◽  
Oxygen Ion ◽  
Average Grain Size ◽  
Vacancy Concentrations

Nanoparticles of yttria-doped tetragonal zirconia polycrystalline ceramics (Y-TZP) with an average crystallite size of less than 9 nm were prepared by a combustion synthesis process. Dense and fine-grained (<200 nm) Y-TZP ceramics were obtained by fast-firing using temperatures lower than 1400 °C and dwell times of less than 2 min. Impedance spectroscopy was employed to measure conductivities of oxygen vacancies in the grain and the grain boundary of the fine-grained Y-TZP. The relationships between the concentration of the oxygen vacancies in the grain boundary and measurable physical parameters were determined semiquantitatively. The oxygen vacancy concentrations and activation energies for the oxygen-ion conduction in the grain and the grain boundary of the fine-grained Y-TZP were found to be independent of the average grain size in the average grain-size range of 90–200 nm. These experimental results suggest that, in order to retain the abnormally high oxygen vacancy concentrations of the Y-TZP nanoparticles and thus enhance the oxygen-ion conductivity, it may be necessary to decrease the average grain size to approximately 10 nm.

First-principles Study of Defect Migration in RE-doped Ceria (RE = Pr, Gd)

2011 ◽  
Vol 1311 ◽  
Author(s):  
Pratik Dholabhai ◽  
James Adams ◽  
Peter Crozier ◽  
Renu Sharma
Keyword(s):  
Oxygen Vacancy ◽  
Density Functional ◽  
Vacancy Formation ◽  
Doped Ceria ◽  
Defect Migration ◽  
Vacancy Migration ◽  
Oxygen Ion ◽  
Oxygen Vacancy Formation ◽  
And Migration ◽  
Migration Pathways

ABSTRACTOxygen vacancy formation and migration in ceria is central to its performance as an ionic conductor. Ceria doped with suitable aliovalent dopants has enhanced oxygen ion conductivity – higher than that of yttria stabilized zirconia (YSZ), the most widely used electrolyte material in solid oxide fuel cells (SOFC). To gain insight into atomic defect migration in this class of promising electrolyte materials, we have performed total energy calculations within the framework of density functional theory (DFT+U) to study oxygen vacancy migration in ceria, Pr-doped ceria (PDC) and Gd-doped ceria (GDC). We report activation energies for various oxygen vacancy migration pathways in PDC and GDC. Results pertaining to the preferred oxygen vacancy formation sites and migration pathways in these materials will be discussed in detail. Overall, the presence of Pr and Gd ions significantly affects oxygen vacancy formation and migration, in a complex manner requiring the investigation of many different migration events. We propose a relationship that explains the role of additional dopants in lowering the activation energy for vacancy migration in PDC and GDC.

Two Different Interactions between Oxygen Vacancies and Dopant Cations for Ionic Conductivity in CaO-Doped CeO2 Electrolyte Materials

2000 ◽  
Vol 658 ◽  
Author(s):  
Yuanzhong Zhou ◽  
Xi Chen
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Low Temperature ◽  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
Electrical Measurement ◽  
Free Oxygen ◽  
Oxygen Ion ◽  
Association Energy ◽  
Defect Interactions

ABSTRACTThe electrical measurement has demonstrated that conductivity of CaO-doped CeO2 has higher activation energy for low temperature and lower activation energy for high temperature. A model with two different kinds of defect interactions between oxygen vacancy and doped cations has been used to interpret the phenomenon. Diffusion based on hopping of oxygen ions was assumed as the mechanism of electrical conduction. The analysis indicated that at high temperature free oxygen vacancies are dominant and the activation energy is only for oxygen ion hopping. At low temperature, however, oxygen vacancies associated with dopant calcium ions are dominant for high CaO content and the activation energy is the energy for hopping of an oxygen ion plus half of the association energy between one oxygen vacancy and one calcium ion. For low level doping, both free and associated oxygen vacancies are important.

Characterization and Modeling of the Conduction and Switching Mechanisms of HfOx Based RRAM

2014 ◽  
Vol 1631 ◽  
Author(s):  
Shimeng Yu ◽  
H.-S. Philip Wong
Keyword(s):  
Oxygen Vacancy ◽  
Resistive Switching ◽  
Oxygen Vacancies ◽  
Conduction Mechanism ◽  
Frequency Noise ◽  
Conductive Filament ◽  
Ion Migration ◽  
Pulse Switching ◽  
Oxygen Ion ◽  
Oxygen Ion Migration

ABSTRACTThe conduction and switching mechanism of resistive random access memory (RRAM) is reviewed in this paper. The resistive switching in oxides is generally attributed to the conductive filament (made up of oxygen vacancies) formation and rupture in the oxide due to field assisted oxygen ion migration. As a model system for device physics study, HfOx based RRAM devices were fabricated and characterized. To identify the electron conduction mechanism, various electrical characterization techniques such as I-V measurements at various temperatures, low-frequency noise measurements, and AC conductance measurements were employed. It was suggested that the trap-assisted-tunneling is the dominant conduction mechanism. In order to explore the oxygen ion migration dynamics, pulse switching measurements were performed. An exponential voltage-time relationship was found between the switching time and the applied voltage. To obtain a first-order understanding of the variability of resistive switching, a Kinetic Monte Carlo (KMC) numerical simulator was developed. The generation/recombination/migration probabilities of oxygen vacancies and oxygen ions were calculated, and the conductive filament configuration was updated stochastically according to those probabilities. The KMC simulation can reproduce many experimental observations in the DC I-V sweep, pulse switching, endurance cycling, and retention baking, etc. The tail bits in the resistance distribution are attributed to the oxygen vacancy left over in the gap region due to a competition between the oxygen vacancy generation and recombination. To enable circuit and system development using RRAM, a compact device model was developed. The compact model, implemented in MATLAB, HSPICE, and Verilog-A, which can be employed in many commonly available circuit simulators using the SPICE engine.

Scalable Oxygen-Ion Transport Kinetics in Metal-Oxide Films: Impact of Thermally Induced Lattice Compaction in Acceptor Doped Ceria Films

2014 ◽  
Vol 24 (11) ◽  
pp. 1562-1574 ◽  
Author(s):  
Jennifer L. M. Rupp ◽  
Emiliana Fabbri ◽  
Dario Marrocchelli ◽  
Jeong-Woo Han ◽  
Di Chen ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Ion Transport ◽  
Oxide Films ◽  
Transport Kinetics ◽  
Doped Ceria ◽  
Metal Oxide Films ◽  
Thermally Induced ◽  
Oxygen Ion

Mechanistic insight into oxygen vacancy migration in SrFeO3–δ from DFT+U simulations

2021 ◽  
Author(s):  
Musa Alaydrus ◽  
Ikutaro Hamada ◽  
Yoshitada Morikawa
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Reduction ◽  
Oxygen Vacancies ◽  
Structural Transitions ◽  
Ion Conductor ◽  
Vacancy Migration ◽  
Oxygen Ion ◽  
Mechanistic Insight ◽  
Oxygen Ion Conductor ◽  
Insight Into

SrFeO3–δ is known to be an effective oxygen ion conductor and oxygen vacancies are central to its performance. SrFeO3–δ displays four crystallographic structural transitions as it undergoes oxygen reduction over...

Chemoselective Hydrogenation of Cinnamaldehyde over Tailored Oxygen Vacancy Rich Pd@ZrO2 Catalyst

2021 ◽  
Author(s):  
Komal N. Patil ◽  
Divya Prasad ◽  
Jayesh T. Bhanushali ◽  
Bhalchandra Kakade ◽  
Arvind H. Jadhav ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Selective Hydrogenation ◽  
Oxygen Vacancies ◽  
Synthesis Method ◽  
Chemoselective Hydrogenation ◽  
Zro2 Catalyst ◽  
Industrial Relevance

Selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde is captivating due to its industrial relevance. Herein, two-step synthesis method was adopted to develop oxygen vacancies in Pd@ZrO2 catalysts. The oxygen vacancies were...

In situ synthesis of Cl-doped Bi2O2CO3 and its enhancement of photocatalytic activity by inducing generation of oxygen vacancies

2020 ◽  
Vol 7 (16) ◽  
pp. 2969-2978
Author(s):  
Jie-hao Li ◽  
Jie Ren ◽  
Ying Liu ◽  
Hui-ying Mu ◽  
Rui-hong Liu ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Ionic Liquids ◽  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
In Situ Synthesis ◽  
Photocatalytic Mechanism

Cl-Doped Bi2O2CO3 is prepared using ionic liquids as dopants and the oxygen-vacancy-induced photocatalytic mechanism is revealed.

A hierarchical oxygen vacancy-rich WO3 with “nanowire-array-on-nanosheet-array” structure for highly efficient oxygen evolution reaction

2019 ◽  
Vol 7 (12) ◽  
pp. 6730-6739 ◽  
Author(s):  
Jinxiang Diao ◽  
Wenyu Yuan ◽  
Yu Qiu ◽  
Laifei Cheng ◽  
Xiaohui Guo
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Evolution Reaction ◽  
Oxygen Vacancies ◽  
State Of The Art ◽  
Nanowire Array ◽  
Nanowire Arrays ◽  
Nanosheet Array ◽  
Nanosheet Arrays ◽  
Array Structure ◽  
First Time

Hierarchical vertical WO3 nanowire arrays on vertical WO3 nanosheet arrays with rich oxygen vacancies were synthesized via a simple and facile method, and the outstanding OER performance which is superior to that of most reported state-of-the-art catalysts was reported for the first time.

scholarly journals Transport Properties and High Temperature Raman Features of Heavily Gd-Doped Ceria

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4148 ◽  
Author(s):  
Cristina Artini ◽  
Sabrina Presto ◽  
Sara Massardo ◽  
Marcella Pani ◽  
Maria Maddalena Carnasciali ◽  
...  
Keyword(s):  
Solid Oxide Fuel Cells ◽  
Oxygen Vacancies ◽  
Arrhenius Plot ◽  
Solid Oxide ◽  
Raman Shift ◽  
Threshold Temperature ◽  
Doped Ceria ◽  
Lower Activation ◽  
Slope Change ◽  
Heavily Doped

Transport and structural properties of heavily doped ceria can reveal subtle details of the interplay between conductivity and defects aggregation in this material, widely studied as solid electrolyte in solid oxide fuel cells. The ionic conductivity of heavily Gd-doped ceria samples (Ce1−xGdxO2−x/2 with x ranging between 0.31 and 0.49) was investigated by impedance spectroscopy in the 600–1000 K temperature range. A slope change was found in the Arrhenius plot at ~723 K for samples with x = 0.31 and 0.34, namely close to the compositional boundary of the CeO2-based solid solution. The described discontinuity, giving rise to two different activation energies, points at the existence of a threshold temperature, below which oxygen vacancies are blocked, and above which they become free to move through the lattice. This conclusion is well supported by Raman spectroscopy, due to the discontinuity revealed in the Raman shift trend versus temperature of the signal related to defects aggregates which hinder the vacancies movement. This evidence, observable in samples with x = 0.31 and 0.34 above ~750 K, accounts for a weakening of Gd–O bonds within blocking microdomains, which is compatible with the existence of a lower activation energy above the threshold temperature.

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