Ludwigites: From natural mineral to modern solid solutions

Софронова, С. Н.; Назаренко, И. И.

doi:10.1002/crat.201600338

Cited by 22 publications

(18 citation statements)

References 57 publications

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“…In the previous reports on BaMnF 4 [29],MnF 2 [30] and MnO [31] the temperature dependence of the lattice dielectric constant has been fitted by modified Barrett equation of the form T = (0)+A/[exp( ω 0 /k B T)-1] where (0) is the expected dielectric constant at 0K, A is a coupling constant and ω 0 is the lowest mean frequency of the final states in the optical phonon branch. A fit using this modified Barrett formalism is indicated by a solid line in Figure (5), yielding (0)=22.664(±0.0008), A=0.80(±0.06), ω 0 =202(±6)cm −1 . It would be interesting to perform Raman or infrared measurements on this system to evaluate if any of the observed modes corresponds to the value which we have deduced from our fitting procedure.…”

Section: Experimental Methodsmentioning

confidence: 99%

Investigations of the heterometallic ludwigite Ni₂AlBO₅

Kumar¹,

Mukkattukavil²,

Bhattacharyya³

et al. 2019

J. Phys.: Condens. Matter

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We present magnetic, thermodynamic, dielectric and structural investigations on the aluminoborate Ni2AlBO5, belonging to the ludwigite family. Room temperature structural refinement suggests that the system crystallizes in the orthorhombic P bam symmetry, in similarity with most members of this material class. Magnetic and thermodynamic measurements shows that the system undergoes a phase transition to an antiferromagnetic state at 38K, signatures of which are also seen in the lattice parameters and the dielectric constant. Short range magnetic correlations appear to persist to much higher temperatures -a regime in which the ac susceptibility exhibits a power law temperature dependence, in agreement with that expected for random exchange Heisenberg antiferromagnetic spin chains.

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Section: Experimental Methodsmentioning

confidence: 99%

Investigations of the heterometallic ludwigite Ni₂AlBO₅

Kumar¹,

Mukkattukavil²,

Bhattacharyya³

et al. 2019

J. Phys.: Condens. Matter

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“…Additionally, there is a possible spin-state crossover of the Co 3+ ions, which are presumably in a low-spin configuration in the magnetically ordered phase (T ≤ 43 K) and in a high-spin configuration at higher temperatures (T 200 K) where the Curie-Weiss paramagnetic behavior is established [12,14,15]. Indeed, the combination of low dimensional units and mixed valence states leads to a number interesting physical phenomena in ludwigites [16,17], such as dimerized states [9], structural and charge-ordering transitions [9,10,14,18,19], spin-glass states [20][21][22][23][24][25][26][27][28], and multiferroicity [29]. Also, these oxyborates have been tested as high-performance electrodes for lithium-ion and sodium-ion batteries [30][31][32][33], low frequency oscillators [34,35], and as oxygen evolution reaction (OER) electrocatalyst [36].…”

Section: Introductionmentioning

confidence: 99%

Structural and spectroscopic investigation of the charge-ordered, short-range ordered, and disordered phases of the Co$_3$O$_2$BO$_3$ ludwigite

Galdino,

Freitas,

Medrano

et al. 2021

Preprint

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Charge-ordering is prone to occur in crystalline materials with mixed-valence ions. It is presumably accompanied by a structural phase transition, with possible exceptions in compounds that already present more than one inequivalent site for the mixed-valence ions in the chargedisordered phase. In this work, we investigate the representative case of the homometallic Co ludwigite Co 2+ 2 Co 3+ O2BO3 (P bam space group) with four distinct Co crystallographic sites [M 1-M 4] surrounded by oxygen octahedra. The mixed-valent character of the Co ions up to at least T = 873 K is verified through x-ray absorption near-edge structure (XANES) experiments. Single crystal x-ray diffraction (XRD) and neutron powder diffraction (NPD) confirm that the Co ions at the M 4 site are much smaller than the others at low temperatures, consistent with a Co 3+ oxidation state at M 4 and Co 2+ at the remaining sites. The size difference between the Co ions in the M 4 and M 2 sites is continuously reduced upon warming above ≈ 370 K, indicating a gradual charge redistribution within the M 4-M 2-M 4 (424) ladder in the average structure. Minor structural anomalies with no space group modification are observed near 475 and 495 K, where sharp phase transitions were previously revealed by calorimetry and electrical resistivity data. An increasing structural disorder, beyond a conventional thermal effect, is noted above ≈ 370 K, manifested by an anomalous increment of XRD Debye-Waller factors and broadened vibrational modes observed by Raman scattering. The local Co-O distance distribution, revealed by Co K-edge Extended X-Ray Absorption Fine Structure (EXAFS) data and analyzed with an evolutionary algorithm method, is similar to that inferred from the XRD crystal structure below ≈ 370 K. At higher temperatures, the local Co-O distance distribution remains similar to that found at low temperatures, at variance with the average crystal structure obtained with XRD. We conclude that the oxidation states Co 2+ and Co 3+ are instantaneously well defined in a local atomic level at all temperatures, however the thermal energy promotes local defects in the charge-ordered configuration of the 424 ladders upon warming. These defects coalesce into a phase-segregated state within a narrow temperature interval (475 < T < 495 K). Finally, a transition at ≈ 500 K revealed by differential scanning calorimetry (DSC) in the iron ludwigite Fe3O2BO3 is discussed.

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“…Oxyborates represent a wide group of compounds, and these have been studied for a considerable time . Although oxyborates grow in different structures, almost all of these structures include low‐dimensional elements such as walls, ladders, chains, and ribbons .…”

Section: Introductionmentioning

confidence: 99%

“…The ludwigites are one of the most interesting groups of oxyborates. Compounds with a ludwigite structure have been widely studied, although it is still unclear which interactions are important in the formation of magnetic ordering in many compounds . For example, the magnetic properties change dramatically when Sn is substituted for Ti in Co 5 Ti(BO 5 ) 2 .…”

Section: Introductionmentioning

confidence: 99%