Exsolution of Nanoparticles on A-site-deficient ferrite perovskites: Its effect on co-electrolysis of CO2 and H2O

2021 ◽  
Author(s):  
Jaesung Kim ◽  
Matthew Ferree ◽  
Seval Gunduz ◽  
Jean-Marc M Millet ◽  
Mimoun Aouine ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Electronic Conductivity ◽  
Structural Diversity ◽  
A Site ◽  
Thermochemical Stability

La0.7Sr0.2Ni0.2Fe0.8O3 (LSNF), having thermochemical stability, superior ionic and electronic conductivity, and structural diversity, was investigated as a cathode in SOECs. Exsolution of nanoparticles by reduction of LSNF at elevated temperatures...

Evaluation of nutrient runoff from the kako river by continuous daily sampling

1996 ◽  
Vol 34 (12) ◽  
pp. 67-72
Author(s):  
Yukio Komai
Keyword(s):  
Suspended Solids ◽  
Water Discharge ◽  
Electronic Conductivity ◽  
High Water ◽  
Nutrient Loads ◽  
Discharge Condition ◽  
Nutrient Runoff ◽  
Average Value ◽  
Daily Sampling ◽  
A Site

A water sample was taken once a day for 15 months at a site near an estuary of the Kako River, Japan, to estimate nutrient loads from rivers to the sea. Total phosphorus (T-P), total nitrogen (T-N), suspended solids (SS) and electronic conductivity (EC) were measured. T-P and SS concentrations varied in proportion to the discharge, and T-P concentrations increased with those of SS, too. EC varied inversely with the discharge, but the fluctuations of T-N concentrations were less than those of T-P and SS concentrations. Water quality remained, for the most part, constant throughout the day. T-P, T-N and SS load were 181t/year, 2320t/year and 51000t/year in 1992, respectively, 54% of T-P load, 47% of T-N load and 80% of SS loads outflowed in those cases where the discharge was more than 100 m3/s, which were 36 days in 1992. 79% of T-P load, 69% of T-N load and 92% of SS load outflowed in periods of high water discharge, which were 88 in 1992. T-P and T-N loads calculated by using one day's data in every month were 151t/year and 2450t/year. But nutrient loads calculated by using the average value of data from an ordinary discharge were two or three times lower than calculated yearly loads. These results showed the importance of estimating the yearly load considering the discharge condition and sampling at a time of high water discharge.

Mixed ionic-electronic conductivity features of A-site deficient Nd nickelates

2020 ◽  
Vol 46 (16) ◽  
pp. 25527-25535 ◽  
Author(s):  
V.A. Sadykov ◽  
E.M. Sadovskaya ◽  
E.A. Filonova ◽  
N.F. Eremeev ◽  
N.M. Bogdanovich ◽  
...  
Keyword(s):  
Electronic Conductivity ◽  
A Site ◽  
Mixed Ionic Electronic Conductivity

Mn-Mg disordering in cummingtonite: a high-temperature neutron powder diffraction study

2000 ◽  
Vol 64 (2) ◽  
pp. 255-266 ◽  
Author(s):  
J. J. Reece ◽  
S. A. T. Redfern ◽  
M. D. Welch ◽  
C. M. B. Henderson
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
New York ◽  
High Temperature ◽  
Powder Diffraction ◽  
Elevated Temperatures ◽  
Neutron Powder Diffraction ◽  
Site Preference ◽  
A Site

AbstractThe crystal structure of a manganoan cummingtonite, composition [M4](Na0.13Ca0.41Mg0.46Mn1.00) [M1,2,3](Mg4.87Mn0.13)(Si8O22)(OH)2, (Z = 2), a = 9.5539(2) Å, b = 18.0293(3) Å, c = 5.2999(1) Å, β = 102.614(2)° from Talcville, New York, has been refined at high temperature using in situ neutron powder diffraction. The P21/m to C2/m phase transition, observed as spontaneous strains +ε1 = −ε2, occurs at ˜107°C. Long-range disordering between Mg2+ and Mn2+ on the M(4) and M(2) sites occurs above 550°C. Mn2+ occupies the M(4) and M(2) sites preferring M(4) with a site-preference energy of 24.6±1.5 kJ mol−1. Disordering induces an increase in XMnM2 and decrease in XMnM4 at elevated temperatures. Upon cooling, the ordered states of cation occupancy are ‘frozen in’ and strains in lattice parameters are maintained, suggesting that re-equilibration during cooling has not taken place.

Preparation and characterization of compounds in the BaBiO3–Ba(Ce1-xGdx)O3-x/2 system

1999 ◽  
Vol 14 (1) ◽  
pp. 124-131 ◽  
Author(s):  
R. Mukundan ◽  
P. K. Davies ◽  
W. L. Worrell
Keyword(s):  
Ionic Conductivity ◽  
Elevated Temperatures ◽  
Electronic Conductivity ◽  
Mixed Valence ◽  
Type Model ◽  
Pseudobinary System ◽  
Conducting Oxides ◽  
Oxygen Ion ◽  
Reducing Conditions ◽  
Electronic Conductivities

The structure, nonstoichiometry, and electrical conductivity of compositions in the BaBiO3– Ba(Ce1-xGdx)O3-x/2 system have been investigated in an attempt to prepare new mixed (ionic-electronic) conducting oxides. The substitution of Bi into Ba(Ce1-xGdx)O3-x/2 decreases the concentration of oxygen-ion vacancies, and the effective negative charge of the Gd dopant is compensated by the mixed valence of Bi (3+, 5+). For low Bi contents a decrease in ionic conductivity decreases the overall conductivity; however, higher levels of Bi introduce significant electronic conductivity, and for Ba(Bi0.5Ce0.5)O3, σtotal ≈ 1 S/cm at 800 °C in air. Compositions in the Ba(Bi0.5Ce0.5-xGdx)O3 pseudobinary system undergo a B-cation order-disorder transformation at 1300–1350 °C for x = 0.5 and at ≈1250 °C for x = 0.4; all other compositions retain a disordered B-site arrangement. While these disordered perovskites exhibit oxygen nonstoichiometry under reducing conditions at elevated temperatures, with the extent of reduction decreasing with increasing Gd content, their ordered counterparts remain close to stoichiometry. The electronic conductivities of this pseudobinary could be fitted to a “band-type” model, and, despite the presence of oxygen vacancies for the lower values of x, no significant ionic conductivity was observed.

Multiple transcripts from the Antennapedia gene of Drosophila melanogaster

1986 ◽  
Vol 6 (12) ◽  
pp. 4667-4675
Author(s):  
V L Stroeher ◽  
E M Jorgensen ◽  
R L Garber
Keyword(s):  
Drosophila Melanogaster ◽  
Alternative Polyadenylation ◽  
Structural Diversity ◽  
Open Reading Frame ◽  
Major Open Reading Frame ◽  
Reading Frame ◽  
Multiple Transcripts ◽  
Temporal Specificity ◽  
Acid Protein ◽  
A Site

The structures of four major transcripts from the homeotic gene Antennapedia of Drosophila melanogaster were determined. These transcripts constitute two RNA classes, each class initiating from a unique promoter but sharing 3' exons. Within the shared sequences is a major open reading frame encoding a 378-amino-acid protein as well as alternative polyadenylation sites. Although the RNA classes differ in their 5' sequences, both leaders contain many AUGs upstream of the major open reading frame. For the two RNA classes, neither gross tissue nor temporal specificity was observed. However, the second poly(A) site is preferred in neural tissue. The structural diversity of the RNAs is discussed in relation to biological functions of the Antennapedia locus.

scholarly journals Multiple transcripts from the Antennapedia gene of Drosophila melanogaster.

1986 ◽  
Vol 6 (12) ◽  
pp. 4667-4675 ◽  
Author(s):  
V L Stroeher ◽  
E M Jorgensen ◽  
R L Garber
Keyword(s):  
Drosophila Melanogaster ◽  
Alternative Polyadenylation ◽  
Structural Diversity ◽  
Open Reading Frame ◽  
Major Open Reading Frame ◽  
Reading Frame ◽  
Multiple Transcripts ◽  
Temporal Specificity ◽  
Acid Protein ◽  
A Site

The structures of four major transcripts from the homeotic gene Antennapedia of Drosophila melanogaster were determined. These transcripts constitute two RNA classes, each class initiating from a unique promoter but sharing 3' exons. Within the shared sequences is a major open reading frame encoding a 378-amino-acid protein as well as alternative polyadenylation sites. Although the RNA classes differ in their 5' sequences, both leaders contain many AUGs upstream of the major open reading frame. For the two RNA classes, neither gross tissue nor temporal specificity was observed. However, the second poly(A) site is preferred in neural tissue. The structural diversity of the RNAs is discussed in relation to biological functions of the Antennapedia locus.

A-site deficient perovskite: the parent for in situ exsolution of highly active, regenerable nano-particles as SOFC anodes

2015 ◽  
Vol 3 (20) ◽  
pp. 11048-11056 ◽  
Author(s):  
Yifei Sun ◽  
Jianhui Li ◽  
Yimin Zeng ◽  
Babak Shalchi Amirkhiz ◽  
Mengni Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Oxygen Vacancies ◽  
Electronic Conductivity ◽  
Nano Particles ◽  
Highly Active ◽  
A Site ◽  
Mobile Oxygen

Introduction of A-site deficiency on Ni-doped LaSrCrO3 anodes helps form highly mobile oxygen vacancies and remarkably enhances Ni nanoparticle reducibility, and significantly increases electronic conductivity and catalytic activity.

Copper scandium zirconium phosphate: occupancy of theM1 andM2 sites in the temperature range 100–300 K

2013 ◽  
Vol 69 (2) ◽  
pp. 105-110 ◽  
Author(s):  
Andrew D. Bond ◽  
Terence E. Warner
Keyword(s):  
Zirconium Phosphate ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Site Occupancy ◽  
Type Structure ◽  
Coordination Geometry ◽  
Threefold Axis ◽  
Circular Distribution ◽  
Nasicon Type ◽  
A Site

The title compound, with nominal formula Cu2ScZr(PO4)3, has a beige coloration and displays fast Cu+cation conduction at elevated temperatures. It adopts a NASICON-type structure in the space groupR\overline{3}c. The examined crystal was an obverse–reverse twin with approximately equal twin components. The [ScIIIZrIV(PO4)3]2−framework is composed of corner-sharing Sc/ZrO6octahedra and PO4tetrahedra. The Sc and Zr atoms are disordered on one atomic site on a crystallographic threefold axis. The P atom of the phosphate group lies on a crystallographic twofold axis. Nonframework Cu+cations occupy three positions. Two of the Cu+positions generate an approximately circular distribution around a site of \overline{3} symmetry, referred to as theM1 site in the NASICON-type structure. The other Cu+position is situated close to the twofold symmetricM2 site, displaced into a position with a distorted square-based pyramidal coordination geometry. The structure has been determined at 100, 200 and 300 K. Changes in the refined site-occupancy factors of the Cu+positions suggest increased mobility of Cu+around the circular orbit close to theM1 site at room temperature, but no movement into or out of theM2 site. Free refinement of the Cu site-occupancy factors suggests that the formula of the crystal is Cu1.92(1)ScZr(PO4)3, which is consistent with the low-level presence of Cu2+exclusively in theM2 site.

scholarly journals Defect chemistry and transport properties of BaxCe0.85M0.15O3-δ

2004 ◽  
Vol 19 (8) ◽  
pp. 2366-2376 ◽  
Author(s):  
J. Wu ◽  
L.P. Li ◽  
W.T.P. Espinosa ◽  
S.M. Haile
Keyword(s):  
Transport Properties ◽  
Elevated Temperatures ◽  
Defect Chemistry ◽  
Gravimetric Analysis ◽  
Barium Cerate ◽  
Charge Balance ◽  
Conducting Oxides ◽  
A Site ◽  
Charged Defects ◽  
Positively Charged

The site-incorporation mechanism of M3+ dopants into A2+B4+O3 perovskites controls the overall defect chemistry and thus their transport properties. For charge-balance reasons, incorporation onto the A2+-site would require the creation of negatively charged point defects (such as cation vacancies), whereas incorporation onto the B4+-site is accompanied by the generation of positively charged defects, typically oxygen vacancies. Oxygen-vacancy content, in turn, is relevant to proton-conducting oxides in which protons are introduced via the dissolution of hydroxyl ions at vacant oxygen sites. We propose here, on the basis of x-ray powder diffraction studies, electron microscopy, chemical analysis, thermal gravimetric analysis, and alternating current impedance spectroscopy, that nominally B-site doped barium cerate can exhibit dopant partitioning as a consequence of barium evaporation at elevated temperatures. Such partitioning and the presence of significant dopant concentrations on the A-site negatively impact proton conductivity. Specific materials examined are BaxCe0.85M0.15O3-δ (x = 0.85 - 1.20; M = Nd, Gd, Yb). The compositional limits for the maximum A-site incorporation are experimentally determined to be: (Ba0.919Nd0.081)(Ce0.919Nd0.081)O3, (Ba0.974Gd0.026)(Ce0.872Gd0.128)O2.875, and Ba(Ce0.85Yb0.15)O2.925. As a consequence of the greater ability of larger cations to exist on the Ba site, the H2O adsorption and proton conductivities of large-cation doped barium cerates are lower than those of small-cation doped analogs.

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