Thermodynamic evaluation and optimization of the BaO-SiO2 and BaO-CaO-SiO2 systems

Shukla, Amar; Jung, In‐Ho; Decterov, Sergei A.; Pelton, Arthur D.

doi:10.1016/j.calphad.2018.03.001

Cited by 11 publications

(5 citation statements)

References 28 publications

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“…Such phenomena could have an effect on the solid solubility, but are largely still unexplored. Margarosanite is stable to ~800°C at ambient pressure (Jak et al , 1998), whereas walstromite has an extended stability to at least 1200°C (Shukla et al , 2018). No data are available for intermediate compositions of the series.…”

Section: Comment On Ba–pb Isomorphismmentioning

confidence: 99%

Instalment of the margarosanite group, and data on walstromite–margarosanite solid solutions from the Jakobsberg Mn–Fe deposit, Värmland, Sweden

Holtstam

Cámara

Karlsson

2021

MinMag

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The margarosanite group (now officially confirmed by IMA-CNMNC) consists of triclinic Ca-(Ba, Pb) cyclosilicates with three-membered [Si3O9]6– rings (3R), with the general formula AB2Si3O9, where A = Pb, Ba and Ca and B = Ca. A closest-packed arrangement of O atoms parallel to (101) hosts Si and B cations in interstitial sites in alternating layers. The 3R layer has three independent Si sites in each ring. Divalent cations occupy three independent sites: Ca in B occupies two nonequivalent sites, Ca1 (8-fold coordinated), and Ca2 (6-fold coordinated). A (=Ca3) is occupied by Pb2+ (or Ba2+) in 6+4 coordination, or 6+1 when occupied by Ca; this third site occurs within the 3R-layer in a peripheral position. Three minerals belong to this group: margarosanite (ideally PbCa2Si3O9), walstromite (BaCa2Si3O9) and breyite (CaCa2Si3O9). So far, no solid solutions involving the Ca1 and Ca2 sites have been described. Therefore, root names depend on the composition of the Ca3 site only. Isomorphic replacement at the Ca3 sites has been noted. We here report data on a skarn sample from the Jakobsberg Mn–Fe oxide deposit, in Värmland, Sweden, representing intermediate compositions on the walstromite–margarosanite binary, in the range ca. 50–70% mol.% BaCa2Si3O9. The Pb-rich walstromite is associated closely with celsian, phlogopite, andradite, vesuvianite, diopside and nasonite. A crystal-structure refinement (R1 = 4.8%) confirmed the structure type, and showed that the Ca3 (Ba, Pb) site is split into two positions separated by 0.39 Å, with the Ba atoms found slightly more peripheral to the 3R-layers.

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Section: Comment On Ba–pb Isomorphismmentioning

confidence: 99%

Instalment of the margarosanite group, and data on walstromite–margarosanite solid solutions from the Jakobsberg Mn–Fe deposit, Värmland, Sweden

Holtstam

Cámara

Karlsson

2021

MinMag

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“…Barium silicates stabilize a wide range of structures from neso-(Q 0 ), ino-(Q 2 ), and phyllo-(Q 3 ) silicates including Ba 2 SiO 4 , BaSiO 3 , and BaSi 2 O 5 which are built from a single Q n species (Eskola 1922;Roth and Levin 1959;Oehlschlegel 1975;Shukla et al 2018). When bonding is between Q n of equal n, e.g.…”

Section: Introductionmentioning

confidence: 99%

A theoretical and experimental investigation of hetero- vs. homo-connectivity in barium silicates

Moulton

Gomes

Cunha

et al. 2022

American Mineralogist

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Barium silicates may be found in contact aureoles and are used in several important technologies (e.g. LEDs). The BaO-SiO 2 system stabilizes 13 crystalline phases with different silicate tetrahedral and connectivity profiles. Aside from phases composed of a single structural unit (isolated or homo-connected tetrahedra) one encounters the relatively rare case of heteroconnected tetrahedra in which varying proportions of several Q n species are linked together. Here, we analyze the 29 Si MAS NMR and Raman spectroscopic manifestations of the connectivities in seven barium silicates: Ba 2 SiO 4 , high-BaSiO 3 , Ba 4 Si 6 O 16 , Ba 5 Si 8 O 21 , Ba 6 Si 10 O 26 , high-BaSi 2 O 5 and sanbornite (low-BaSi 2 O 5 ). The structures and purity of these phases were confirmed by Rietveld refinement. From the Raman spectroscopic database on 144predominantly homo-connected crystalline silicates, the mean Q n mode frequencies (ν Qn ± 1σ) are found at 827.7 (±13.8) cm -1 for Q 0 , 905.3 (±22.1) cm -1 for Q 1 , 993.5 (±25.9) cm -1 for Q 2 , and 1068.4 (±17.6) cm -1 for Q 3 units. Experimentally, homo-connected barium silicates show good agreement with these values whereas the hetero-connected phases show a wider range of ν Q2 than of ν Q3 frequencies. While the 29 Si NMR chemical shifts of the barium silicates are in agreement with known structural trends, those measured for the Q 2 resonances remain essentially constant, which may be caused by the lattice distortion around the large Ba 2+ cations. To complement and rationalize experimental measurements, first-principles calculations, at the This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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“…36-1449). Here, there is no discernable peak related with impurities, indicating that the co-dopants (D y 3+ /Tb 3+ ) are appropriately incorporated into the hexagonal Ba 1.3 Ca 0.7 SiO 4 phosphors with space group (p3false¯m1) [16,17,23]. Figure 1 b shows the crystal structure of alkaline earth-based tetra silicate, Ba 1.3 Ca 0.7 SiO 4 , constructed by using the VESTA ( visualization for electronic structural analysis ) software.…”

Section: Resultsmentioning

confidence: 99%

Photoluminescence processes in τ -phase Ba _1.3 Ca _{0.7-
x
-
y} SiO ₄ : x D y ³⁺ / y Tb ³⁺ phosphors for solid-state lighting

et al. 2022

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The τ -phase Ba 1.3 Ca 0.7- x - y SiO 4 : x D y 3+ / y Tb 3+ phosphors co-doped with D y 3+ ( x = 0.03) and Tb 3+ ( y = 0.01–0.05) trivalent rare-earth ions were prepared by the gel-combustion method. The structure–property relation of the samples was examined by X-ray diffraction, scanning electron microscopy and spectrophotometer. Here, the effect of Tb 3+ 's concentration on the spectroscopic properties of Ba 1.3 Ca 0.7- x - y SiO 4 : x D y 3+ / y Tb 3+ phosphors was explored by using the photoluminescence excitation, emission and decay curves. Importantly, the photonic energy transfer from (D y 3+ : 4 F 9/2 + Tb 3+ : 7 F 6 ) to (D y 3+ : 6 H 15/2 + Tb 3+ : 5 D 4 ) was observed, in which the D y 3+ ions act as a light-emitting donor whereas the Tb 3+ ions as a light-absorbing acceptor, resulting in an enhanced emission from the co-doped Ba 1.3 Ca 0.7- x - y SiO 4 : x D y 3+ / y Tb 3+ ( x = 0.03 and y = 0.01–0.05) phosphors. Finally, the chromaticity coordinates were determined from the measured emission spectra, locating at the green and white light regions. This observation indicates that the characteristic emission colour could be tuned from white to green by varying Tb 3+ concentrations under ultraviolet light.

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Thermodynamic evaluation and optimization of the BaO-SiO2 and BaO-CaO-SiO2 systems

Cited by 11 publications

References 28 publications

Instalment of the margarosanite group, and data on walstromite–margarosanite solid solutions from the Jakobsberg Mn–Fe deposit, Värmland, Sweden

Instalment of the margarosanite group, and data on walstromite–margarosanite solid solutions from the Jakobsberg Mn–Fe deposit, Värmland, Sweden

A theoretical and experimental investigation of hetero- vs. homo-connectivity in barium silicates

Photoluminescence processes in τ -phase Ba _1.3 Ca _{0.7-
x
-
y} SiO ₄ : x D y ³⁺ / y Tb ³⁺ phosphors for solid-state lighting

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Thermodynamic evaluation and optimization of the BaO-SiO2 and BaO-CaO-SiO2 systems

Cited by 11 publications

References 28 publications

Instalment of the margarosanite group, and data on walstromite–margarosanite solid solutions from the Jakobsberg Mn–Fe deposit, Värmland, Sweden

Instalment of the margarosanite group, and data on walstromite–margarosanite solid solutions from the Jakobsberg Mn–Fe deposit, Värmland, Sweden

A theoretical and experimental investigation of hetero- vs. homo-connectivity in barium silicates

Photoluminescence processes in τ -phase Ba 1.3 Ca 0.7- x - y SiO 4 : x D y 3+ / y Tb 3+ phosphors for solid-state lighting

Contact Info

Product

Resources

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Photoluminescence processes in τ -phase Ba _1.3 Ca _{0.7-
x
-
y} SiO ₄ : x D y ³⁺ / y Tb ³⁺ phosphors for solid-state lighting