scholarly journals Understanding Carbon Contamination in the Proton-Conducting Zirconates and Cerates

2021 ◽  
Author(s):  
Andrew J. E. Rowberg ◽  
Michael W Swift ◽  
Chris G Van de Walle
Keyword(s):  
First Principles ◽  
First Principles Calculations ◽  
Carbon Contamination ◽  
Proton Conducting ◽  
Conducting Oxides

Carbon contamination is a significant concern for proton-conducting oxides in the cerate and zirconate family, particularly for BaCeO3. Here, we use first-principles calculations to evaluate carbon stability in SrCeO3, BaCeO3,...

Surface defect chemistry of Y-substituted and hydrated BaZrO3 with subsurface space-charge regions

2016 ◽  
Vol 4 (19) ◽  
pp. 7437-7444 ◽  
Author(s):  
Jonathan M. Polfus ◽  
Tor S. Bjørheim ◽  
Truls Norby ◽  
Rune Bredesen
Keyword(s):  
Surface Layer ◽  
Space Charge ◽  
Space Charge Region ◽  
First Principles ◽  
Surface Defect ◽  
Surface Defects ◽  
Defect Chemistry ◽  
First Principles Calculations ◽  
Proton Conducting ◽  
Charged Species

First-principles calculations were utilized to elucidate the complete defect equilibria of surfaces of proton conducting BaZrO3, encompassing charged species adsorbed to the surface, defects in the surface layer as well as in the subsurface space-charge region and bulk.

Solubility of transition metal interstitials in proton conducting BaZrO3 and similar perovskite oxides

2016 ◽  
Vol 4 (21) ◽  
pp. 8105-8112 ◽  
Author(s):  
Jonathan M. Polfus ◽  
Marie-Laure Fontaine ◽  
Annett Thøgersen ◽  
Marit Riktor ◽  
Truls Norby ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
First Principles ◽  
Perovskite Oxides ◽  
Defect Chemistry ◽  
First Principles Calculations ◽  
Proton Conducting

The defect chemistry of foreign transition metals in perovskite oxides was investigated by first-principles calculations in combination with experiments with focus on Ni and Zn in Y-doped BaZrO3.

Electronic Structure and X-ray Absorption Spectra of Rutile TiO2 Using First-Principles Calculations

2014 ◽  
Vol 52 (12) ◽  
pp. 1025-1029
Author(s):  
Min-Wook Oh ◽  
Tae-Gu Kang ◽  
Byungki Ryu ◽  
Ji Eun Lee ◽  
Sung-Jae Joo ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Absorption Spectra ◽  
First Principles ◽  
First Principles Calculations ◽  
Rutile Tio2 ◽  
X Ray ◽  
X Ray Absorption

Interaction of H2O, O2 and H2 with Proton Conducting Oxides Based on Lanthanum Scandates

2019 ◽  
pp. 88-100
Author(s):  
A. S. Farlenkov ◽  
N. A. Zhuravlev ◽  
Т. A. Denisova ◽  
М. V. Ananyev
Keyword(s):  
Water Vapor ◽  
Partial Pressure ◽  
Gas Phase ◽  
Molecular Hydrogen ◽  
Proton Magnetic Resonance ◽  
Partial Pressure Of Oxygen ◽  
Proton Conducting ◽  
Conducting Oxides ◽  
Temperature Range ◽  
Apparent Level

The research uses the method of high-temperature thermogravimetric analysis to study the processes of interaction of the gas phase in the temperature range 300–950 °C in the partial pressure ranges of oxygen 8.1–50.7 kPa, water 6.1–24.3 kPa and hydrogen 4.1 kPa with La1–xSrxScO3–α oxides (x = 0; 0.04; 0.09). In the case of an increase in the partial pressure of water vapor at a constant partial pressure of oxygen (or hydrogen) in the gas phase, the apparent level of saturation of protons is shown to increase. An increase in the apparent level of saturation of protons of the sample also occurs with an increase in the partial pressure of oxygen at a constant partial pressure of water vapor in the gas phase. The paper discusses the causes of the observed processes. The research uses the hydrogen isotope exchange method with the equilibration of the isotope composition of the gas phase to study the incorporation of hydrogen into the structure of proton-conducting oxides based on strontium-doped lanthanum scandates. The concentrations of protons and deuterons were determined in the temperature range of 300–800 °C and a hydrogen pressure of 0.2 kPa for La0.91Sr0.09ScO3–α oxide. The paper discusses the role of oxygen vacancies in the process of incorporation of protons and deuterons from the atmosphere of molecular hydrogen into the structure of the proton conducting oxides La1–xSrxScO3–α (x = 0; 0.04; 0.09). The proton magnetic resonance method was used to study the local structure in the temperature range 23–110 °C at a rotation speed of 10 kHz (MAS) for La0.96Sr0.04ScO3–α oxide after thermogravimetric measurements in an atmosphere containing water vapor, and after exposures in molecular hydrogen atmosphere. The existence of proton defects incorporated into the volume of the investigated proton oxide from both the atmosphere containing water and the atmosphere containing molecular hydrogen is unambiguously shown. The paper considers the effect of the contributions of the volume and surface of La0.96Sr0.04ScO3–α oxide on the shape of the proton magnetic resonance spectra.

To Bend or Not to Bend, the Dilemma of Multiple Bonds

2019 ◽  
Author(s):  
Michele Pizzocchero ◽  
Matteo Bonfanti ◽  
Rocco Martinazzo
Keyword(s):  
First Principles ◽  
2D Materials ◽  
Main Group ◽  
First Principles Calculations ◽  
Group 14 ◽  
Multiple Bonds ◽  
Main Group Elements ◽  
Structural Distortions

The manuscript addresses the issue of the structural distortions occurring at multiple bonds between high main group elements, focusing on group 14. These distortions are known as trans-bending in silenes, disilenes and higher group analogues, and buckling in 2D materials likes silicene and germanene. A simple but correlated \sigma + \pi model is developed and validated with first-principles calculations, and used to explain the different behaviour of second- and higher- row elements.

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

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