The AFeO2 (A=K, Rb and Cs) family: A comparative study of structures and structural phase transitions

Ali, Nazim; Nuß, Jürgen; Sheptyakov, Denis; Jansen, Martin

doi:10.1016/j.jssc.2010.01.022

Cited by 45 publications

(52 citation statements)

References 45 publications

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“…) which exhibits a symmetrical doublet with isomer shift and quadruple splitting values of 0.32 and 0.72 mm/s, respectively. These parameters are in agreement with those reported already in literature . 21 TEM analysis (Fig.…”

Section: Resultssupporting

confidence: 93%

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Synthesis of Nanosized Cesium Ferrite by Precursor and Combustion Method: A Comparative Study

Gupta

Randhawa

2012

Int J Applied Ceramic Tech

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Thermolysis of cesium hexa(carboxylato)ferrate(III) precursors, Cs 3 [Fe(L) 6 ].xH 2 O (L = formate, acetate, propionate, butyrate), has been carried out in flowing air atmosphere from ambient temperature to 1000°C. Various physico-chemical techniques, that is, simultaneous TG-DTG-DTA, XRD, TEM, IR, Mössbauer spectroscopy, have been employed to characterize the intermediates and end products. After dehydration, the anhydrous precursors undergo exothermic decomposition to yield various intermediates, that is, cesium carbonate/propionate/butyrate and a-Fe 2 O 3 . A subsequent decomposition of these intermediates leads to the formation of cesium ferrite above 800°C. Similar ferrite has been prepared by the combustion method at comparatively lower temperature (600°C) and in less time than that of conventional ceramic method.

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Section: Resultssupporting

confidence: 93%

“…XRD powder pattern (Fig. ) of the final thermolysis residue also reveals the existence of CsFeO 2 with CsAlO 2 type geometry . TEM analysis (Fig.…”

Section: Resultsmentioning

confidence: 77%

Synthesis of Nanosized Cesium Ferrite by Precursor and Combustion Method: A Comparative Study

Gupta

Randhawa

2012

Int J Applied Ceramic Tech

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“…Oddly, this consideration creates an additional iron atom in the referenced volume, whose origin cannot be explained. In fact, the structure determination of the β’’‐type crystal yielded the composition K 1.81 Fe 10.73 O 17 , i. e. in our consideration, an oxoferrate sum formula close to Fe 32 O 51 . Hence, it seems highly probable that additional voids on iron positions exist (as in γ −Fe 2 O 3 ) and the “idealized” sum formula of a crystal obtained by decomposition of K 2− x Fe 4 O 7− x (OH) x should be K 2 Fe 10.67 O 17 .…”

Section: Resultsmentioning

confidence: 62%

Oxo‐Hydroxoferrate K_2−xFe₄O_7−x(OH)_x: Hydroflux Synthesis, Chemical and Thermal Instability, Crystal and Magnetic Structures

et al. 2019

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The reaction of Fe(NO3)3⋅9 H2O with KOH under hydroflux conditions at about 200 °C produces red crystals of K2−xFe4O7−x(OH)x in a quantitative yield. In the crystal structure, edge‐sharing [FeO6] octahedra form ∞2[ Fe2O6] honeycomb nets. Pillars consisting of pairs of vertex‐sharing [FeO4] tetrahedra link the honeycomb layers and form columnar halls in which the potassium ions are located. The trigonal (P true3‾ 1m) and the hexagonal (P63/mcm) polytypes of K2−xFe4O7−x(OH)x show oriented intergrowth. The sub‐stoichiometric potassium content (x≈0.3) is compensated by hydroxide ions. K2−xFe4O7−x(OH)x is an antiferromagnet above 2 K and its magnetic structure was determined by neutron powder diffraction. Under ambient conditions, K2−xFe4O7−x(OH)x hydrolyzes and K2CO3 ⋅ H2O forms gradually on the surface of the K2−xFe4O7−x(OH)x crystals. Upon annealing at air at about 500 °C, the potassium atoms in the columnar halls start to order into a superstructure. The thermal decomposition of K2−xFe4O7−x(OH)x proceeds via a topotactic transformation into K1+x′Fe11O17, adopting the rhombohedral β’’ or the hexagonal β‐aluminate‐type structure, before γ‐Fe2O3 is formed above 950 °C, which then converts into thermodynamically stable α‐Fe2O3.

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“…The room temperature AFeO 2 (A = K, Rb and Cs) structures are of the KGaO 2 type and contain six member rings of corner-sharing FeO 4 tetrahedra that are connected to adjacent rings by additional corner-sharing. 3 Na 14 Fe 6 O 16 contains linked 4- and 6-member rings of corner sharing FeO 4 tetrahedra, 4 while in Ba 3 NbFe 3 Si 2 O 14 , FeO 4 tetrahedra form trimers that are interconnected via NbO 6 octahedra. 5 Other iron containing ring structures include Na 10 Fe 4 O 9 , 6 and Ba 3 Fe 2 O 6 7 In most iron containing oxides the rings are interconnected but exceptions exist, including the FeO 4 tetrahedra trimers in Ba 3 NbFe 3 Si 2 O 14 , 5 and the 12-member rings in Ba 3 Fe 2 O 6 .…”

Section: Introductionmentioning

confidence: 99%

Ba₄KFe₃O₉: A Novel Ferrite Containing Discrete 6-Membered Rings of Corner-Sharing FeO₄ Tetrahedra

Zhao¹,

Nellutla

Son

et al. 2011

Inorg. Chem.

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Single crystals of a new iron containing oxide, Ba4KFe3O9, were grown from a hydroxide melt and the crystal structure was determined by single crystal x-ray diffraction. This ferrite represents the first complex oxide containing isolated 6-member rings of corner sharing FeO4 tetrahedra. Mössbauer measurements are indicative of two tetrahedral high-spin Fe3+ coordination environments. The observed magnetic moment (~3.9 BM) at 400 K is significantly lower than the calculated spin-only (~5.2 BM) value indicating the presence of strong antiferromagnetic interactions in the oxide. Our density functional calculations confirm the strong antiferromagnetic coupling between adjacent Fe3+ sites within each 6-member ring and estimate the nearest neighbor spin exchange integral as ~200 K; next nearest neighbor interactions are shown to be negligible. The lower than expected effective moment for Ba4KFe3O9 calculated from χT data is explained as resulting from the occupation of lower lying magnetic states in which more spins are paired. X-band (9.5 GHz) electron paramagnetic resonance (EPR) spectra of powder sample consist of a single line at g~2.01 that is characteristic of Fe3+ ions in a tetrahedral environment, thus, confirming the Mössbauer results. Further analysis of the EPR line shape reveals the presence of two types of Fe6 magnetic species with an intensity ratio of ~1:9. Both species have Lorentzian line shapes and indistinguishable g-factors but differ in the peak-to-peak line widths (δBpp). The line width ratio δBpp(major)/δBpp(minor) ~ 3.6 correlates well with the ratio of the Weiss constants, θminor/θmajor ~ 4.

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The AFeO2 (A=K, Rb and Cs) family: A comparative study of structures and structural phase transitions

Cited by 45 publications

References 45 publications

Synthesis of Nanosized Cesium Ferrite by Precursor and Combustion Method: A Comparative Study

Synthesis of Nanosized Cesium Ferrite by Precursor and Combustion Method: A Comparative Study

Oxo‐Hydroxoferrate K_2−xFe₄O_7−x(OH)_x: Hydroflux Synthesis, Chemical and Thermal Instability, Crystal and Magnetic Structures

Ba₄KFe₃O₉: A Novel Ferrite Containing Discrete 6-Membered Rings of Corner-Sharing FeO₄ Tetrahedra

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The AFeO2 (A=K, Rb and Cs) family: A comparative study of structures and structural phase transitions

Cited by 45 publications

References 45 publications

Synthesis of Nanosized Cesium Ferrite by Precursor and Combustion Method: A Comparative Study

Synthesis of Nanosized Cesium Ferrite by Precursor and Combustion Method: A Comparative Study

Oxo‐Hydroxoferrate K2−xFe4O7−x(OH)x: Hydroflux Synthesis, Chemical and Thermal Instability, Crystal and Magnetic Structures

Ba4KFe3O9: A Novel Ferrite Containing Discrete 6-Membered Rings of Corner-Sharing FeO4 Tetrahedra

Contact Info

Product

Resources

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Oxo‐Hydroxoferrate K_2−xFe₄O_7−x(OH)_x: Hydroflux Synthesis, Chemical and Thermal Instability, Crystal and Magnetic Structures

Ba₄KFe₃O₉: A Novel Ferrite Containing Discrete 6-Membered Rings of Corner-Sharing FeO₄ Tetrahedra