Optical spectra of Cr3+ ions in tetrahedral coordination in an inverted spinel LiGa5O8

Sviridov, D. T.; Sviridova, R. K.

doi:10.1007/bf00614226

Cited by 7 publications

(9 citation statements)

References 3 publications

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“…It is known that Cr 3+ dopant ions in inorganic compounds exhibit a strong tendency to possess an octahedral coordination. On the contrary, Cr 3+ ions in tetrahedral coordination are very rare. − The four-coordinated Cr 3+ ions have been shown to exist in systems such as Cr-bearing blue-colored diopsides, Cr-heteropolytungstate, Na 4 CrO 4 , several Cr-containing inverted spinels, Cr-doped Bi 12 SiO 20 , and several organometallic compounds. − One of the fundamental problems in the structure determination of Cr-doped materials is the potential coexistence of several oxidation states of chromium in the materials under study (Cr 2+ , Cr 3+ , Cr 4+ , Cr 5+ , or Cr 6+ ), making the spectroscopic fingerprinting of tetrahedral Cr 3+ difficult. − …”

Section: Introductionmentioning

confidence: 99%

Chromium Environment within Cr-Doped BaAl₂O₄: Correlation of X-ray Diffraction and X-ray Absorption Spectroscopy Investigations

Vrankić¹,

Gržeta²,

Lützenkirchen‐Hecht

et al. 2015

Inorg. Chem.

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Powder BaAl2O4 samples doped with 0 and 1.76 atom % Cr in relation to Al were hydrothermally prepared. Both samples were characterized by X-ray diffraction and synchrotron based X-ray absorption spectroscopy at the Cr K- and the Ba L3-edge. Diffraction patterns indicated that samples were nanocrystalline with a hexagonal crystal structure, space group P63. Chromium doping of barium aluminate caused an increase of the unit-cell volume and diffraction line broadening. The doped sample contained a small amount of an impurity phase, namely, BaCrO4. Analyzed Cr K-edge X-ray absorption near edge structure for the doped sample showed the presence of chromium in 6+ and 3+ oxidation states: Cr(6+) was characteristic for chromium in the impurity phase BaCrO4, while Cr(3+) participated in the formation of the doped phase BaAl2O4:Cr. Extended X-ray absorption fine structure suggested an unusual tetrahedral coordination of Cr(3+) ions within the BaAl2O4 host phase. The structure of samples was refined by the Rietveld method, simultaneously with the analysis of diffraction line broadening. Rietveld structure refinement showed that in doping the Cr(3+) ions likely substituted for Al(3+) ions on Al1 tetrahedral sites of barium aluminate crystal lattice. Crystallite sizes in the samples decreased with chromium doping, from 32 nm for pure BaAl2O4 to 24 nm for Cr-doped BaAl2O4. The dopant Cr(3+) cations acted as defects in the barium aluminate structure that increased lattice strain from 0.02% for pure BaAl2O4 to 0.14% for doped BaAl2O4 and disturbed the crystallites to grow.

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Section: Introductionmentioning

confidence: 99%

Chromium Environment within Cr-Doped BaAl₂O₄: Correlation of X-ray Diffraction and X-ray Absorption Spectroscopy Investigations

Vrankić¹,

Gržeta²,

Lützenkirchen‐Hecht

et al. 2015

Inorg. Chem.

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“…[37,43] However, V 3+ ions, similarly to the Cr 3+ ions, dominantly occupy octahedral environments when forming regular sublattice in crystals and only enter tetrahedral sites as dopants. [43,44] Thus, they are unfavored by condition (i). Tetrahedrally coordinated Mn +2 ions carry S=5/2 spins, hence, a strong magnetooptical response from these ions is excluded by condition (ii).…”

Section: B Diagonal and Off-diagonal Optical Conductivity Spectramentioning

confidence: 99%

Strong magneto-optical effects in ACr2O4 ( A=Fe,Co ) spinel oxides generated

et al. 2018

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Magneto-optical effects have been investigated over the infrared-visible spectral range in ACr2O4 (A = Fe, Co) spinel oxides with non-collinear spin orders in their ground states. We found large magneto-optical Kerr rotation and ellipticity at the on-site d-d transitions of the A 2+ ions located within the charge gap. The magneto-optical Kerr rotation of ϑKerr ≈ 12 deg observed in CoCr2O4 is unprecedentedly large among magnetic semiconductors and points towards the uniqueness of tetrahedrally coordinated Co 2+ ions in generating strong magneto-optical response. Criteria of strong magneto-optical effects emerging at on-site d-d transitions of transition metal ions are discussed.

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“…As earlier discussed in the Introduction, tetrahedral oxygen coordination is very uncommon for chromium(III) and was reported before only for several spinels. [28][29][30][31][32][33] Unfortunately, optical characterisation of these compounds was performed only for a few inverted spinels based on LiGa 5−x Cr x O 8 , where chromium atoms occupy both, octahedral and tetrahedral positions. 32,33,39 On the basis of the presented data in those publications it is very difficult to attribute with certainty the spectrum components, which appear in the visible part of the spectrum, and to distinguish the absorption bands corresponding to electronic transition of chromium(III) in a different crystallographic environment and to compare it with our result.…”

Section: Dalton Transactions Papermentioning

confidence: 99%

“…However, tetrahedral coordination is very uncommon for chromium(III) and its realisation with oxygen has been reported only for a few spinels. [28][29][30][31][32][33] To the best of our knowledge, chromium(III) occupies octahedral positions in all known phosphates. The preferable octahedral coordination of chromium(III) can be explained in terms of crystal field stabilisation energy and, specifically, octahedral site preference energy, which is one of the highest for d 3 electronic configuration of Cr(III).…”

Section: Introductionmentioning

confidence: 99%

“…The preferable octahedral coordination of chromium(III) can be explained in terms of crystal field stabilisation energy and, specifically, octahedral site preference energy, which is one of the highest for d 3 electronic configuration of Cr(III). 32,34 Thus, from the point of view of crystallographic preference of Cr(III), its location in the charge-compensating tetrahedral sites of the SW lattice may cause some constraint and instability of the resulting structural formation. This paper examines whether the considered concept makes sense and verifies the possibility of formation of Cr 1/3 Zr 2 P 3 O 12 .…”

Section: Introductionmentioning

confidence: 99%

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Cr_1/3Zr₂P₃O₁₂ with unusual tetrahedral coordination of Cr(iii): peculiarities of the formation, thermal stability and application as a pigment

et al. 2014

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All the known chromium(III) NASICON-related phosphates are considered to be solid solutions. In these compounds chromium atoms share their position in the basic framework of the crystal lattice with other structure forming elements such as zirconium. In our study, we have hypothesised a completely new way of structural organisation of the chromium(III) zirconium(IV) NASICON framework, consisting in the distribution of chromium over the charge-compensating atom sites with tetrahedral oxygen coordination. The possibility of formation of the corresponding phosphate, Cr(1/3)Zr2P3O12, was studied using a classical ceramic route and a sol-gel method. Structural affiliation of the obtained pure phase product was studied using XRD analysis. The results confirmed that the Cr(1/3)Zr2P3O12 phosphate belongs to monoclinic SW-subtype of the NASICON family. In this structure, chromium atoms occupy charge-compensating sites with a strongly distorted tetrahedral oxygen environment. To the best of our knowledge, it is the first example of tetrahedral coordination of chromium(III) in phosphates. Along with the unusual crystallographic characteristics of chromium, special attention in this paper is devoted to the thermal stability of this phosphate and to its performance as an inorganic pigment. The sample was characterised by heating microscopy and DTA study, particle size distribution analysis, and IR- and VIS-spectroscopy. The stability of the obtained powder in a glaze environment, its colouring performance and lightfastness are discussed as well.

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Optical spectra of Cr3+ ions in tetrahedral coordination in an inverted spinel LiGa5O8

Cited by 7 publications

References 3 publications

Chromium Environment within Cr-Doped BaAl₂O₄: Correlation of X-ray Diffraction and X-ray Absorption Spectroscopy Investigations

Chromium Environment within Cr-Doped BaAl₂O₄: Correlation of X-ray Diffraction and X-ray Absorption Spectroscopy Investigations

Strong magneto-optical effects in ACr2O4 ( A=Fe,Co ) spinel oxides generated

Cr_1/3Zr₂P₃O₁₂ with unusual tetrahedral coordination of Cr(iii): peculiarities of the formation, thermal stability and application as a pigment

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Optical spectra of Cr3+ ions in tetrahedral coordination in an inverted spinel LiGa5O8

Cited by 7 publications

References 3 publications

Chromium Environment within Cr-Doped BaAl2O4: Correlation of X-ray Diffraction and X-ray Absorption Spectroscopy Investigations

Chromium Environment within Cr-Doped BaAl2O4: Correlation of X-ray Diffraction and X-ray Absorption Spectroscopy Investigations

Strong magneto-optical effects in ACr2O4 ( A=Fe,Co ) spinel oxides generated

Cr1/3Zr2P3O12 with unusual tetrahedral coordination of Cr(iii): peculiarities of the formation, thermal stability and application as a pigment

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Chromium Environment within Cr-Doped BaAl₂O₄: Correlation of X-ray Diffraction and X-ray Absorption Spectroscopy Investigations

Chromium Environment within Cr-Doped BaAl₂O₄: Correlation of X-ray Diffraction and X-ray Absorption Spectroscopy Investigations

Cr_1/3Zr₂P₃O₁₂ with unusual tetrahedral coordination of Cr(iii): peculiarities of the formation, thermal stability and application as a pigment