Crystal Structure of Hollandite

Byström, Anders; Byström, Ann Marie

doi:10.1038/1641128a0

Cited by 22 publications

(15 citation statements)

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“…A Ba- and Cs-containing hollandite is predicted to form during fabrication of multiphase ceramics from melt processing 2 . Hollandite has a general formula of A x (Ti,B) 8 O 16 and structurally consists of TiO 6 and BO 6 octahedra, with A-site cations held within the tunnel cavities 3 . Cs is known to incorporate into the A-site tunnels of hollandite during processing, while other dopants such as Zn and Ga are incorporated as B-site cations to maintain charge neutrality 4 .…”

Section: Introductionmentioning

confidence: 99%

Atomistic scale investigation of cation ordering and phase stability in Cs-substituted Ba1.33Zn1.33Ti6.67O16, Ba1.33Ga2.66Ti5.67O16 and Ba1.33Al2.66Ti5.33O16 hollandite

Wen

Brinkman

et al. 2018

Sci Rep

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The titanate-based hollandite structure is proposed as an effective ceramic waste form for Cs-immobilization. In this study, quantum-mechanical calculations were used to quantify the impact of A-site and B-site ordering on the structural stability of hollandite with compositions BaxCsy(MzTi8-z)O16, where M = Zn2+, Ga3+, and Al3+. The calculated enthalpy of formation agrees with experimental measurements of related hollandite phases from melt solution calorimetry. Ground state geometry optimizations show that, for intermediate compositions (e.g., CsBaGa6Ti18O48), the presence of both Cs and Ba in the A-site tunnels is not energetically favored. However, the decay heat generated during storage of the Cs-containing waste form may overcome the energetics of Ba and Cs mixing in the tunnel structure of hollandite. The ability of the hollandite structure to accommodate the radioparagenesis of Cs to Ba is critical for long term performance of the waste. For the first time, B-site ordering was observed along the tunnel direction ([001] zone axis) for the Ga-hollandite compositions, as well as the intermediate Al-hollandite composition. These compositionally dependent structural features, and associated formation enthalpies, are of importance to the stability and radiation damage tolerance of ceramic waste forms.

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Section: Introductionmentioning

confidence: 99%

Atomistic scale investigation of cation ordering and phase stability in Cs-substituted Ba1.33Zn1.33Ti6.67O16, Ba1.33Ga2.66Ti5.67O16 and Ba1.33Al2.66Ti5.33O16 hollandite

Wen

Brinkman

et al. 2018

Sci Rep

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“…The transformations that occur during solid-phase interaction of fluorides and natural aluminum silicates are quite complex and involve the formation of metastable intermediate compounds such as fluorotopaz, fluorine-substituted analogs of aluminum silicates (substitution of OH -by F -), or gaseous fluorides. These interactions are examined in detail on mixtures of kaolin and pyrophyllite with aluminum fluoride [6,7].…”

Section: Resultsmentioning

confidence: 99%

“…8d), the same admixtures are present in smaller amounts and the cordierite content reaches 95 vol.% based on petrography. Unlike hydrogen fluoride that adapts to the structure of natural minerals by replacement of hydroxyl group by fluorine [6,7], hydrochloric and especially sulfuric acids destruct it partially or completely [8,9]. This results in the formation of amorphous silica and water-soluble salts and in the extraction of alkaline oxides and CaO during treatment of deposited alumina hydroxide.…”

Section: Synthesis Of Cordierite From Chemically Activated Mineralsmentioning

confidence: 99%

Mechanochemical activation of kaolin, pyrophyllite, and talcum and its effect on the synthesis of cordierite and properties of cordierite ceramics

Pavlikov

Garmash

Yurchenko

et al. 2011

Powder Metall Met Ceram

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The paper examines the mechanochemical activation of starting minerals (kaolin, pyrophyllite, and talcum) and their effect on the solid-phase synthesis and properties of cordierite. Binary oxide compounds (spinel, mullite, enstatite, forsterite) are synthesized. It is established that binary compounds and crystalline silica should be minimized to decrease the synthesis temperature of cordierite. Processes for synthesis and production of cordierite ceramics with lower thermal expansion coefficient ((1.0-1.2) ⋅ 10 -6 °C -1 ) are developed.

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“…[134,[143][144][145] Hollandite and todorokite have similar tunneled structures with lattices of edge sharing MnO6 octahedra organized in a 2×2 and 3×3 fashion, respectively. [126,[145][146][147][148] A study of the two phases by Kumagai et al showed that todorokite was a more suitable host for Mg ions, being able to intercalate up to 0.3 Mg per Mn atom. [145] It was also shown that hollandite can intercalate 0.16…”

Section: Mg-ion Batterymentioning

confidence: 99%

Chemical Flexibility of Mg in Pnictide Materials: Structure and Properties Diversity

et al. 2019

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Magnesium, element no. 12 on the periodic table, is the second member of the alkaline-earth metal family. Often, Mg is considered as an electropositive metal like its heavier congeners, Ca, Sr, and Ba. In this review, another important aspect of Mg chemistry, namely, the ability to form covalent bonds to more electronegative elements, is considered with a focus on pnictides. Magnesium's flexible coordination numbers and bond distances are similar to those of main group elements (Al) or late-and post-transition metals (Mn, Cu, Zn, Cd). In this work, selected Mg-pnictides are discussed to emphasize the chemical and structural diversity of Mg which results in a variety of physical properties. Thermoelectric, Mg-ion battery, and nonlinear optical applications of select Mg-containing compounds are summarized, providing examples on the exploitation of Mg chemical bonding flexibility for the design of novel functional materials.

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Crystal Structure of Hollandite

Cited by 22 publications

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Atomistic scale investigation of cation ordering and phase stability in Cs-substituted Ba1.33Zn1.33Ti6.67O16, Ba1.33Ga2.66Ti5.67O16 and Ba1.33Al2.66Ti5.33O16 hollandite

Atomistic scale investigation of cation ordering and phase stability in Cs-substituted Ba1.33Zn1.33Ti6.67O16, Ba1.33Ga2.66Ti5.67O16 and Ba1.33Al2.66Ti5.33O16 hollandite

Mechanochemical activation of kaolin, pyrophyllite, and talcum and its effect on the synthesis of cordierite and properties of cordierite ceramics

Chemical Flexibility of Mg in Pnictide Materials: Structure and Properties Diversity

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