Induction of Bidimensionality in CU-TI Perovskttes

1994 ◽  
Vol 346 ◽  
Author(s):  
M.R. Palacín ◽  
A. Fuertes ◽  
N. Casañ-Pastor ◽  
P. Gómez-Romero
Keyword(s):  
Oxygen Vacancies ◽  
Three Dimensional ◽  
Cation Substitution ◽  
Layered Oxides ◽  
Octahedral Sites

ABSTRACTThe synteses and structure of the three-dimensional perovskite LajCuTiOg are described. In this oxide Cu and Ti atoms are disordered among octahedral sites. The introduction of oxygen vacancies by an adequate cation substitution leads to the induction of bidimensionality as well as an ordered arrangement of cations and oxygen vacancies as found in the layered oxides Ln2Ba2Cu2Ti2O11 (Ln=La,Nd,Eu).

X-Ray and Optical Data for a Vanadium-rich Dravite from Silver Knob, Mariposa County, California, U.S.A.

1992 ◽  
Vol 7 (4) ◽  
pp. 236-238 ◽  
Author(s):  
Franklin F. Foit
Keyword(s):  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Divalent Cation ◽  
Optical Data ◽  
Cation Substitution ◽  
X Ray ◽  
Octahedral Sites ◽  
Cell Dimensions ◽  
Compositional Variability ◽  
Unit Cell Dimensions

AbstractX-ray powder diffraction and optical data are presented for a vanadium-rich dravite from Silver Knob, Mariposa County, California, U.S.A. The limited compositional variability observed for vanadium-rich dravite is due to the presence of a Tschermaks substitution whereby the substitution of Al for Si in the tetrahedral ring is charge balanced by trivalent for divalent cation substitution in the octahedral sites in the structure. Vanadium-rich dravite is uniaxial negative with ε = 1.646(2) and ω = 1.676(2). Refined unit cell dimensions are a = 15.9599(10) and c = 7.1889(2); F30 = 111(0.009; 30); M20 = 80; and Dx = 3.07. An indexed X-ray powder diffraction pattern is also presented.

scholarly journals Uncovering the roles of oxygen vacancies in cation migration in lithium excess layered oxides

2014 ◽  
Vol 16 (28) ◽  
pp. 14665-14668 ◽  
Author(s):  
Danna Qian ◽  
Bo Xu ◽  
Miaofang Chi ◽  
Ying Shirley Meng
Keyword(s):  
Oxygen Vacancies ◽  
Layered Oxides ◽  
Cation Migration

scholarly journals Crystal Chemistry of Chlormagaluminite, Mg4Al2(OH)12Cl2(H2O)2, a Natural Layered Double Hydroxide

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 221 ◽  
Author(s):  
Elena S. Zhitova ◽  
Sergey V. Krivovichev ◽  
Igor V. Pekov ◽  
Vasiliy O. Yapaskurt
Keyword(s):  
Crystal Structure ◽  
Crystal Structure Data ◽  
Three Dimensional ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
Average Chemical Composition ◽  
X Ray ◽  
Octahedral Sites ◽  
Double Hydroxide ◽  
Oh Content

Chlormagaluminite is the only Cl-dominated hydrotalcite-supergroup mineral species with M2+:M3+ = 2:1. The holotype sample of chlormagaluminite from the Kapaevskaya volcanic pipe (Irkutsk Oblast, Siberia, Russia) has been chemically and structurally characterized. The average chemical composition of the mineral is (electron microprobe, OH content is calculated by stoichiometry and H2O from the crystal-structure data, wt. %): MgO 33.85, FeO 1.09, Al2O3 22.07, Cl 14.72, H2Otot 30.96, Cl=O −3.39, total 99.30. The empirical formula based on Mg + Al + Fe = 6 atoms per formula unit (apfu) is [Mg3.91Fe2+0.07Al2.02(OH)12]Cl2.02(H2O)2.0(2). The crystal structure has been solved from single-crystal X-ray diffraction data in the space group P63/mcm, a = 5.268(3), c = 15.297(8) Å and V = 367.6(4) Å3. The refinement converged to R1 = 0.083 on the basis of 152 unique reflections with I > 2σ(I) collected at room conditions. The powder pattern contains standard reflections of a 2H polytype and two additional reflections [(010), d010 = 4.574 Å; (110), d110 = 2.647 Å] indicative of Mg and Al ordering according to the superstructure. The structure is based upon brucite-type octahedral layers with an ordered distribution of Mg and Al over octahedral sites. The Cl− anions and H2O molecules reside in the interlayer, providing a three-dimensional integrity of the structure.

Insight into physicochemical properties of Nd2CuO4±δ and the A-site cation deficient Nd1.9CuO4±δ layered oxides

2020 ◽  
Vol 13 (06) ◽  
pp. 2051034
Author(s):  
Bartłomiej Gȩdziorowski ◽  
Anna Niemczyk ◽  
Anna Olszewska ◽  
Kacper Cichy ◽  
Konrad Świerczek
Keyword(s):  
Crystal Structure ◽  
Electrical Conductivity ◽  
Physicochemical Properties ◽  
Oxygen Vacancies ◽  
Numerical Density ◽  
Interstitial Oxygen ◽  
Layered Oxides ◽  
Oxygen Defects ◽  
A Site ◽  
Insight Into

Nd2CuO[Formula: see text] is known to possess either oxygen vacancies or interstitial oxygen defects, depending on the synthesis route, as well as may exhibit the A-site deficiency. In this work, insight into physicochemical properties of Nd2CuO[Formula: see text] and Nd[Formula: see text]CuO[Formula: see text] layered oxides is given, focusing on the crystal structure, electrical conductivity, and oxygen permeation, as well as on numerical density functional theory (DFT) simulations concerning ionic defects formation and their possible movement in the crystal structure. The results indicate that in oxidizing conditions at low temperatures, interstitial oxygen defects are stable, but with the increase of temperature, the release of oxygen is observed, leading to formation of the oxygen vacancies. Both materials are stable at elevated temperatures in air and Ar. Larger oxygen nonstoichiometry and improved electrical conductivity at high temperatures for Nd[Formula: see text]CuO[Formula: see text] compound are accompanied by the recorded oxygen flux of ca. 0.2[Formula: see text]mL[Formula: see text]cm[Formula: see text][Formula: see text]min[Formula: see text] at 880∘C for 0.8[Formula: see text]mm thick ceramic membrane.

CeO2-Induced Interfacial Co2+ Octahedral Sites and Oxygen Vacancies for Water Oxidation

ACS Catalysis ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 6484-6490 ◽  
Author(s):  
Bocheng Qiu ◽  
Cong Wang ◽  
Ning Zhang ◽  
Lejuan Cai ◽  
Yujie Xiong ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Oxygen Vacancies ◽  
Octahedral Sites

The crystal structure of phlogopite by neutron diffraction

1974 ◽  
Vol 39 (308) ◽  
pp. 850-856 ◽  
Author(s):  
J. H. Rayner
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Study ◽  
Three Dimensional ◽  
Site Occupancy ◽  
Fluorine Content ◽  
Neutron Diffraction Study ◽  
Hydroxyl Group ◽  
Octahedral Sites

SummaryThe positions of all the atoms including hydrogen have been found by a partial three-dimensional single-crystal neutron-diffraction study in which about one-third of the reflections in the reciprocal sphere to 1·5 Å were measured. The hydroxyl group is perpendicular to the plane of the silicate sheets. The fluorine content of this phlogopite is enough to occupy 25 % of the (OH, F) sites. Site occupancy refinement suggests that there is a small deficiency of hydrogen at the remaining sites and that the two crystallographically different octahedral sites are fully occupied by the same proportions of Mg, Ti, Fe, and Ca.

scholarly journals An Idealised Approach of Geometry and Topology to the Diffusion of Cations in Honeycomb Layered Oxide Frameworks

2020 ◽  
Author(s):  
Godwill Mbiti Kanyolo ◽  
Titus Masese
Keyword(s):  
Three Dimensional ◽  
Quantum Geometry ◽  
Layered Oxides ◽  
Alkali Cations ◽  
Layered Oxide ◽  
Quantum Tunnelling ◽  
Quantum Properties ◽  
Curvature Deformation ◽  
Topological Phase Transitions

<div><p>Honeycomb layered oxides are a novel class of nanostructured materials comprising alkali or alkaline earth metals intercalated into transition metal slabs. The intricate honeycomb architecture and layered framework endows this family of oxides with a tessellation of features such as exquisite electrochemistry, unique topology and fascinating electromagnetic phenomena. Despite having innumerable functionalities, these materials remain highly underutilized as their underlying atomistic mechanisms are vastly unexplored. Therefore, in a bid to provide a more in-depth perspective, we propose an idealised diffusion model of the charged alkali cations (such as lithium, sodium or potassium) in the two-dimensional (2D) honeycomb layers within the three-dimensional (3D) crystal of honeycomb layered oxide frameworks. This model not only explains the correlation between the excitation of cationic vacancies (by applied electromagnetic fields) and the Gaussian curvature deformation of the 2D surface, but also takes into consideration, the quantum properties of the cations and their inter-layer mixing through quantum tunnelling. Through this work, we offer a novel theoretical framework for the study of 3D layered materials with 2D cationic diffusion currents, as well as providing pedagogical insights into the role of topological phase transitions in these materials in relation to Brownian motion and quantum geometry.<br></p></div>

A Heuristic Model for 3D Layered Materials with 2D Cationic Diffusion Currents from Their Honeycomb Lattice

2020 ◽  
Author(s):  
Godwill Mbiti Kanyolo ◽  
Titus Masese
Keyword(s):  
Three Dimensional ◽  
Layered Materials ◽  
Honeycomb Structure ◽  
Honeycomb Lattice ◽  
Heuristic Model ◽  
Layered Oxides ◽  
Alkali Cations ◽  
Quantum Properties ◽  
Curvature Deformation

<div><p>Honeycomb layered oxides are a novel class of materials generally exhibiting high ionic conductivity with battery applications. Owing to their honeycomb structure and layered framework, this class of materials is thought to harbor unique electrochemistry and physics. Here, a heuristic diffusion model of the charged alkali cations (such as lithium, sodium or potassium) in two-dimensional (2D) honeycomb layers within the three-dimensional (3D) crystal of honeycomb layered oxide is proposed. The model relates the excitation of cationic vacancies (by applied electromagnetic fields) to the Gaussian curvature deformation of the 2D surface. The quantum properties of the cations and their interlayer mixing through quantum tunneling are also considered. This work offers a novel theoretical framework for the study of 3D layered materials with 2D cationic diffusion currents, whilst providing pedagogical insights in the role of geometry in Brownian motion and quantum theory.</p><br></div>

Unveiling the benefits of potassium doping on the structural integrity of Li–Mn-rich layered oxides during prolonged cycling by dual-mode EPR spectroscopy

2019 ◽  
Vol 21 (43) ◽  
pp. 24017-24025 ◽  
Author(s):  
Jianyin Wang ◽  
Mengchu Yang ◽  
Chong Zhao ◽  
Bei Hu ◽  
Xiaobing Lou ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Epr Spectroscopy ◽  
Oxygen Vacancies ◽  
Structural Integrity ◽  
Transition Metal Ions ◽  
Layered Oxides ◽  
Dual Mode

The migration of transition-metal ions and oxygen vacancies in the Li1.2Mn0.6Ni0.2O2 cathode is mitigated after K+ bulk doping.

Sign in / Sign up

Export Citation Format

Share Document