Monoclinic structure and nonstoichiometry of `KAlSiO<sub>4</sub>-<i>O1</i>'

Kremenović, Aleksandar; Lazić, Biljana; Krüger, Hannes; Tribus, Martina; Vulić, Predrag

doi:10.1107/s0108270113006069

Cited by 9 publications

(3 citation statements)

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“…In addition, an abstract reported a kalsilite structure in space group P6322 (Uchida et al 2006). Kalsilite having monoclinic symmetry has been reported by Kremenović et al (2013). The kalsilite structure was studied at high temperature (Kawahara et al 1987) and high pressure (Gatta et al 2011).…”

Section: Kalsilitementioning

confidence: 99%

Structural variations across the nepheline (NaAlSiO4)–kalsilite (KAlSiO4) series

Antao

Hovis

2021

American Mineralogist

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The crystal structure of 19 samples from the nepheline (NaAlSiO4; Ne)-kalsilite (KAlSiO4; Ks) series, previously prepared via ion-exchange, were examined using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements. Parent materials for the three series include a natural Monte Somma nepheline (series-1), synthetic Na nepheline (series-2), and high-Si synthetic nepheline (series-3) having excess Si mole percentages of 5.2%, 1.7%, and 12.5%, respectively. Three different structure-types were found to occur among the samples examined: nepheline (P63), tetrakalsilite (P63), and kalsilite (both P63 and P31c intergrowth). Trikalsilite was not observed in this study. Vacancies () at the K site as well as Ca and K atoms at the Na1 site play an important role in the crystal chemical behaviour of nepheline solid solutions. Vacancies cause an elongation in the average [9] distance in nepheline. When K atoms enter the Na1 site in nepheline, the average <(Na,K)-O>[7] distance increases linearly and is parallel to the average <(Na,K)-O>[9] distance in kalsilite and the grand mean of such distances in trikalsilite and tetrakalsilite. Before K atoms enter the Na1 site, the average <(Na,K)-O>[7] distance is constant because of the full occupancy of the Na1 site with Na atoms. Ca atoms at the Na1 site in the Monte Somma sample-1 cause a contraction in the <(Na,K)-O>[7] distance. In Na-rich nepheline samples, Na atoms in the large channels occupy a Na(K) site that is off the 63 axis and close to the usual K site. In natural nepheline samples, the K site in most cases contains K atoms and , and the Na1 site is filled mainly with Na, minor Ca, and K atoms in K-rich samples. Nepheline from Monte Somma (sample-1) contains weak satellite reflections that are also present in some other kalsilite samples. Average distances indicate a high degree of Al-Si disorder in nepheline, but increasing Al-Si order in tetrakalsilite and kalsilite. Increasing the amount of K atoms beyond the ideal composition of K0.25Na0.75[AlSiO4] causes expansion in multiple structural parameters because of the larger size of K + relative to Na + .

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Section: Kalsilitementioning

confidence: 99%

Structural variations across the nepheline (NaAlSiO4)–kalsilite (KAlSiO4) series

Antao

Hovis

2021

American Mineralogist

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“…30 for leucite and Kremenovic et al . 31 for KAlSiO 4 -O1. Parameters were refined following Novembre et al .…”

Section: Methodsmentioning

confidence: 96%

Synthesis and Characterization of Leucite Using a Diatomite Precursor

Novembre

Gimeno

Poe

2019

Sci Rep

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Leucite is nowadays an important component in ceramic restoration systems with particular suitability to dental porcelains. The leucite synthesis from a hydrothermally-derived precursor is here presented. A silicate solution was prepared by mixing a naturally derived amorphous silica (diatomitic rock from Crotone, southern Italy) with potassium hydroxide and an aluminate solution was obtained by mixing aluminium hydroxide and potassium hydroxide. Three mixtures of varying ratios of aluminate and silicate solutions were prepared and submitted to hydrothermal treatment at 150 °C for one hour. Subsequently these hydrothermal precursors were subjected to calcination at the temperature of 1000 °C for variable time intervals, thus resulting in 3 series of syntheses. The synthesis run 3 turned out to be the best from the point of view of temporal yield showing the crystallization of the leucite after only 15 hours of heat treatment. The products of synthesis run 3 were fully characterised by Powder X-Ray Diffraction, Inductively Coupled Plasma Optical Emission Spectrometry, Infrared Spectroscopy and Thermal Analysis. The amorphous phase in the synthesis powders was estimated by quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. Density of leucite was also achieved by He-pycnometry. The use of a cost effective starting material such as a diatomite in the experimental route makes the process highly attractive for expansion to an industrial scale especially considering that both the chemical and physical characterizations of our leucite product are highly satisfactory. Last but not least we explain some inferences that can be obtained from this process of synthesis in order to a better understanding of some natural occurrences of leucite in geologic systems related to basaltic magmas.

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“…The O1 phase was eventually shown to be monoclinic (Gregorkiewitz, 1980), with a new topology based on two different kinds of rings, (1-2-3) and (1-2-4). Its crystal structure was finally refined in space group P2 1 using a combination of X-ray powder diffraction and 29 Si magic angle spinning nuclear magnetic resonance (MAS-NMR) data (Gregorkiewitz et al, 2008), and from twinned single-crystal X-ray diffraction (Kremenović et al, 2013). A natural occurrence of O1 was recently reported in the Hatrurim Complex, Negev Desert, Israel (Krü ger et al, 2016).…”

Section: Phasementioning

confidence: 99%

The structure of kaliophilite KAlSiO₄, a long-lasting crystallographic problem

Mugnaioli

Bonaccorsi

Lanza

et al. 2020

Int Union Crystallogr J

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Kaliophilite is a feldspathoid mineral found in two Italian magmatic provinces and represents one of the 12 known phases with composition close to KAlSiO4. Despite its apparently simple formula, the structure of this mineral revealed extremely complex and resisted structure solution for more than a century. Samples from the Vesuvius–Monte Somma and Alban Hills volcanic areas were analyzed through a multi-technique approach, and finally the crystal structure of kaliophilite was solved using 3D electron diffraction and refined against X-ray diffraction data of a twinned crystal. Results were also ascertained by the Rietveld method using synchrotron powder intensities. It was found that kaliophilite crystallizes in space group P3 with unit-cell parameters a = 27.0597 (16), c = 8.5587 (6) Å, V = 5427.3 (7) Å3 and Z = 54. The kaliophilite framework is a variant of the tridymite topology, with alternating SiO4 and AlO4 tetrahedra forming sheets of six-membered rings (63 nets), which are connected along [001] by sharing the apical oxygen atoms. Considering the up (U) and down (D) orientations of the linking vertex, kaliophilite is the first framework that contains three different ring topologies: nine (1-3-5) (UDUDUD) rings, six (1-2-3) (UUUDDD) rings and twelve (1-2-4) (UUDUDD) rings. This results in a relatively open (19.9 tetrahedra nm−3) channel system with multiple connections between the double six-ring cavities. Such a framework requires a surprisingly large unit cell, 27 times larger than the cell of kalsilite, the simplest phase with the same composition. The occurrence of some Na for K substitution (3–10%) may be related to the characteristic structural features of kaliophilite. Micro-twinning, pseudo-symmetries and anisotropic hkl-dependent peak broadening were also detected, and they may account for the elusive character of the kaliophilite crystal structure.

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Monoclinic structure and nonstoichiometry of `KAlSiO₄-O1'

Cited by 9 publications

References 9 publications

Structural variations across the nepheline (NaAlSiO4)–kalsilite (KAlSiO4) series

Structural variations across the nepheline (NaAlSiO4)–kalsilite (KAlSiO4) series

Synthesis and Characterization of Leucite Using a Diatomite Precursor

The structure of kaliophilite KAlSiO₄, a long-lasting crystallographic problem

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Monoclinic structure and nonstoichiometry of `KAlSiO4-O1'

Cited by 9 publications

References 9 publications

Structural variations across the nepheline (NaAlSiO4)–kalsilite (KAlSiO4) series

Structural variations across the nepheline (NaAlSiO4)–kalsilite (KAlSiO4) series

Synthesis and Characterization of Leucite Using a Diatomite Precursor

The structure of kaliophilite KAlSiO4, a long-lasting crystallographic problem

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Product

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Monoclinic structure and nonstoichiometry of `KAlSiO₄-O1'

The structure of kaliophilite KAlSiO₄, a long-lasting crystallographic problem