Impact of transition metal oxidation state on the multiferroic properties and magnetoelectric coupling strength of BST ceramics

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.

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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

Current Applied Physics ◽

10.1016/j.cap.2017.11.019 ◽

2018 ◽

Vol 18 (2) ◽

pp. 155-162 ◽

Cited By ~ 4

Author(s):

V.R. Galakhov ◽

D.I. Turkin ◽

V.V. Mesilov ◽

S.N. Shamin ◽

G.V. Bazuev ◽

...

Keyword(s):

Crystal Structure ◽

Transition Metal ◽

Oxidation State ◽

Magnetic Ordering ◽

Metal Oxidation ◽

X Ray Diffraction ◽

X Ray ◽

X Ray Absorption

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X-ray absorption to determine the metal oxidation state of transition metal compounds

10.1063/1.4813463 ◽

2013 ◽

Cited By ~ 1

Author(s):

J. Jiménez-Mier ◽

P. Olalde-Velasco ◽

G. Carabalí-Sandoval ◽

G. Herrera-Pérez ◽

E. Chavira ◽

...

Keyword(s):

Transition Metal ◽

Oxidation State ◽

Transition Metal Compounds ◽

Metal Oxidation ◽

Metal Compounds ◽

X Ray ◽

X Ray Absorption

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Piperazine as an Inexpensive and Efficient Ligand for Pd-Catalyzed Homocoupling Reactions to Synthesize Bipyridines and Their Analogues

Current Organic Synthesis ◽

10.2174/1570179415666180913131905 ◽

2019 ◽

Vol 16 (1) ◽

pp. 173-180

Author(s):

Mingwei Chen ◽

Jinyu Hu ◽

Xiaoli Tang ◽

Qiming Zhu

Keyword(s):

Transition Metal ◽

Oxidation State ◽

Coupling Reaction ◽

Aryl Halides ◽

Metal Species ◽

Good Substrate ◽

Active Metal ◽

Homocoupling Reaction ◽

Catalytic Cycles ◽

Reductive Homocoupling

Aim and Objective: The synthesis of bipyridines, especially 2, 2’-bipyridines, remains challenging because the catalytic cycle can be inhibited due to coordination of bipyridine to transition metal. Thus, the development of efficient methods for the synthesis of bipyridines is highly desirable. In the present work, we presented a promising approach for preparation of bipyridines via a Pd-catalyzed reductive homocoupling reaction with simple piperazine as a ligand. Materials and Methods: Simple and inexpensive piperazine was used as a ligand for Pd-catalyzed homocoupling reaction. The combination of Pd(OAc)2 and piperazine in dimethylformamide (DMF) was observed to form an excellent catalyst and efficiently catalyzed the homocoupling of azaarenyl halides, in which DMF was used as the solvent without excess reductants although stoichiometric reductant was generally required to generate the low-oxidation-state active metal species in the catalytic cycles. </P><P> Results: In this case, good to excellent yields of bipyridines and their (hetero) aromatic analogues were obtained in the presence of 2.5 mol% of Pd(OAc)2 and 5 mol% of piperazine, using K3PO4 as a base in DMF at 140°C. Conclusion: According to the results, piperazine as an inexpensive and efficient ligand was used in the Pd(OAc)2-catalyzed homocoupling reaction of heteroaryl and aryl halides. The coupling reaction was operationally simple and displayed good substrate compatibility.

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Transition metal chemistry in synthetically viable alkaline earth complexes M(Cp)3– (M = Ca, Sr, Ba)

Chemical Communications ◽

10.1039/d1cc01753e ◽

2021 ◽

Author(s):

Bin Huo ◽

Rui Sun ◽

Bo Jin ◽

Lingfei Hu ◽

Jian-Hong Bian ◽

...

Keyword(s):

Transition Metal ◽

Oxidation State ◽

Alkaline Earth ◽

Transition Metal Chemistry ◽

Metal Chemistry

We predicted the stable alkaline earth complexes M(Cp)3– (M = Ca, Sr, Ba; Cp = cyclopentadienyl), where the M centers were in their stable +2 oxidation state and mimicked the...

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