Effect of transition metal oxidation state on crystal structure and magnetic ordering in frustrated A BaM 4 O 7 systems (A= Y, Ca; M= Co, Fe): X-ray diffraction, soft X-ray absorption, and magnetization studies

2018 ◽  
Vol 18 (2) ◽  
pp. 155-162 ◽  
Author(s):  
V.R. Galakhov ◽  
D.I. Turkin ◽  
V.V. Mesilov ◽  
S.N. Shamin ◽  
G.V. Bazuev ◽  
...  
2009 ◽  
Vol 64 (3) ◽  
pp. 281-286 ◽  
Author(s):  
Suliman Nakhal ◽  
Wilfried Hermes ◽  
Thorsten Ressler ◽  
Rainer Pöttgen ◽  
Martin Lerch

Ammonolysis of vanadium sulfide leads to the formation of bixbyite-type vanadium oxide nitrides. Small amounts of nitrogen incorporated in the structure result in the stabilization of the bixbyite type not known for vanadium oxides. The crystal structure was investigated using X-ray diffraction and X-ray absorption spectroscopy. At temperatures above 550 °C the powders decompose to corundumtype V2O3 containing no detectable amount of nitrogen. Below 39 K magnetic ordering is observed.


2013 ◽  
Author(s):  
J. Jiménez-Mier ◽  
P. Olalde-Velasco ◽  
G. Carabalí-Sandoval ◽  
G. Herrera-Pérez ◽  
E. Chavira ◽  
...  

2006 ◽  
Vol 932 ◽  
Author(s):  
Neil C. Hyatt ◽  
Martin C. Stennett ◽  
Steven G. Fiddy ◽  
Jayne S. Wellings ◽  
Sian S. Dutton ◽  
...  

ABSTRACTA range of transition metal bearing hollandite phases, formulated Ba1.2B1.2Ti6.8O16 (B2+ = Mg, Co, Ni, Zn, Mn) and Ba1.2B2.4Ti5.6O16 (B3+ = Al, Cr, Fe) were prepared using an alkoxide - nitrate route. X-ray powder diffraction demonstrated the synthesis of single phase materials for all compositions except B = Mn. The processing conditions required to produce > 95 % dense ceramics were determined for all compositions, except B = Mg for which the maximum density obtained was > 93 %. Analysis of transition metal K-edge XANES data confirmed the presence of the targeted transition metal oxidation state for all compositions except B = Mn, where the overall oxidation state was found to be Mn3+. The K-edge EXAFS data of Ba1.2B1.2Ti6.8O16 (B = Ni and Co) were successfully analysed using a crystallographic model of the hollandite structure, with six oxygen atoms present in the first co-ordination shell at a distance of ca. 2.02Å. Analysis of Fe K-edge EXAFS data of Ba1.2B2.4Ti5.4O16 revealed a reduced co-ordination shell of five oxygens at ca. 1.99Å.


1990 ◽  
Vol 210 ◽  
Author(s):  
C. Lévy-Clèment ◽  
C. Mondoloni ◽  
C. Godart ◽  
R. Cortès

AbstractThis paper presents applications of in situ X-ray diffraction and absorption techniques to the study of H+/MnO2 alkaline batteries. The two complementary in situ techniques are described. Investigation of the electrochemical insertion and deinsertion of H+ has been made through its influence on the evolution of the crystallographic structure of γ-MnO2, while investigation of the transfer of e has been undertaken through the variation of the oxidation state of the manganese during the discharging and charging process of a battery. New insights in the understanding of the mechanisms of proton insertion and charge transfer into γ-MnO2 are discussed.


Polyhedron ◽  
2004 ◽  
Vol 23 (17) ◽  
pp. 2631-2636 ◽  
Author(s):  
Alan Bailey ◽  
William P. Griffith ◽  
David W.C. Leung ◽  
Andrew J.P. White ◽  
David J. Williams

2018 ◽  
Vol 9 (33) ◽  
pp. 6813-6829 ◽  
Author(s):  
Markus Kubin ◽  
Meiyuan Guo ◽  
Thomas Kroll ◽  
Heike Löchel ◽  
Erik Källman ◽  
...  

A combined experimental and theoretical approach reveals correlations of metal L-edge X-ray absorption energies to local charge and spin densities.


2021 ◽  
Vol 1016 ◽  
pp. 231-235
Author(s):  
Shota Ando ◽  
Hiromi Nakano ◽  
Koichiro Fukuda

We have been investigating the series of P doped Ca2SiO4 (C2S) using Eu2+ or Eu3+ as activator with various colors. The crystal structure of C2S is particularly easily controlled by heating because the established polymorphs of C2S are, in the order of increasing temperature, γ, β, α’L, α’H, and α. In order to control the crystal structure, the phosphors were synthesized and then annealed at temperatures 1473 K-1773 K. The crystal structures and PL properties were compared between slow cooling and quenching (cooled in water). We found unique phenomena when the phosphors were treated by quenching process. In the case of (Ba1-xCax)2(Si0.94P0.06)O4:Eu3+ ( 0.25 ≤ x ≤ 1), color emission changed from red to blue-white for the phosphor with a high concentration of Ba and quenched at 1773 K. In general, Eu3+ doped phosphors showed the red emission color in any host materials. However, Ba-included and quenched-treatment phosphors emitted a bright white color. The mechanism and relationship between the PL property and crystal structure were characterized carefully using X-ray diffraction, electron microscope and X-ray absorption fine structure.


2004 ◽  
Vol 835 ◽  
Author(s):  
N. Tran ◽  
L. Croguennec ◽  
F. Weill ◽  
C. Jordy ◽  
P. Biensan ◽  
...  

ABSTRACTLayered Li1+x(Ni0.425Mn0.425Co0.15)1−xO2 materials (x = 0 and 0.12) have been prepared by a coprecipitation method. The substitution of × Li+ ions for × metal ions in the transition metal layers leads to an increase in the average transition metal oxidation state for charge compensation, which was found to be due to the oxidation of Ni2+ ions into Ni3+ ions. The refinement in the R-3m space group of the X-ray diffraction data has shown an increasing lamellar character for the structure of these materials, with increasing overlithiation. Electron diffraction has revealed the presence of a √3.ahex. × √3.ahex. superstructure due to a cationic ordering in the transition metal layers, those being packed with faults along the chex.-axis. From an electrochemical point of view, the reversible capacity in the 2–4.3V decreased with overlithiation, in agreement with a decreasing amount of exchangeable electrons.


2018 ◽  
Vol 20 (28) ◽  
pp. 19129-19141 ◽  
Author(s):  
Stefan Permien ◽  
Tobias Neumann ◽  
Sylvio Indris ◽  
Gero Neubüser ◽  
Lorenz Kienle ◽  
...  

Transition metal cations on the move: simultaneous operando XAS and XRD investigations during Li uptake and release of a NiFe2O4/CNT composite.


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