On the ambient pressure polymorph of K2Ca3Si3O10—An unusual mixed-anion silicate and its structural and spectroscopic characterization

Schmidmair, Daniela; Kahlenberg, Volker; Perfler, Lukas; Tribus, Martina; Hildebrandt, Johannes; Többens, Daniel M.

doi:10.1016/j.jssc.2015.04.019

Cited by 15 publications

(15 citation statements)

References 31 publications

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“…The insufficient experimental data in the system limits the calculation result. Moreover, recently a new compound, K 2 O•3CaO•3SiO 2 synthesized at high pressure was reported by Arroyabe et al [25] and is also stable at 1 atm, as reported by Schmidmair et al [26,27], who also found a new compound K 2 O•CaO•4SiO 2 . Thus, inclusion of these two new compounds in the calculation will affect the results of the previous critical assessments.…”

Section: Introductionmentioning

confidence: 66%

Phase equilibria and liquid phase behavior of the K2O-CaO-SiO2 system for entrained flow biomass gasification

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Paek

et al. 2020

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Experimental data of solid-liquid phase equilibria in the K 2 O-CaO-SiO 2 systems vital for many technologies and industrial applications are very limited and even not available at some primary phase fields. In the present study, by using Equilibration-Quenching-Phase compositional analysis (EPMA/EDS) method, liquidus compositions in equilibrium with pure solid SiO 2 , CaO•SiO 2 , 3CaO•2SiO 2 , 2CaO•SiO 2 , K 2 O•6CaO•4SiO 2 and K 2 O•2CaO•2SiO 2 compounds and 2CaO•SiO 2 solid solution were measured. By knowing the evaporation behavior of K 2 O during the equilibration process, specific initial mixtures could be selected to obtain liquidus data for targeted final equilibrium assemblages. EPMA and EDS analysis results were compared. The experimental data obtained in the present study were discussed and compared with the results from previous experimental investigations and the assessed ternary phase diagrams. Some novel experimental data of the liquid at single and double solid phase saturations were obtained in the present study and they can be used to correct and support the predictions and thermodynamic assessments of the K 2 O-CaO-SiO 2 system. Present investigation reports liquidus projections and detailed phase relations among the phases in isothermal sections at 1000, 1100, 1200, 1300 and 1400°C. Viscosity calculations of the liquid at different compositions between 1000 and 1400°C also have been made. A combination of phase equilibria study and the viscosity predictions in the present investigation provides suitable temperature and ash composition regions for optimal flow properties of the slag in entrained flow biomass combustion or gasification processes.

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Section: Introductionmentioning

confidence: 66%

Phase equilibria and liquid phase behavior of the K2O-CaO-SiO2 system for entrained flow biomass gasification

Santoso

Taskinen

Paek

et al. 2020

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“…Our own studies performed during the last years arouse suspicion not only with respect to the number of crystalline phases that have been previously described in the literature, but also concerning their chemical composition. In summary one can state that (a) some of the phases mentioned by Morey and co-autors 1 [5][6][7][8] and (d) at least one compound (K 2 CaSiO 4 ) 9 has to be disconfirmed. Furthermore, extensive solid solutions among the potassium calcium silicates seem to be virtually absent.…”

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confidence: 95%

“…From a structural point of view this is probably due to the pronounced differences in the ionic radii between K + and Ca 2+ (r K [6] : 1.38 Å, r Ca [6] : 1.00 Å) 10 .…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, extensive solid solutions among the potassium calcium silicates seem to be virtually absent. From a structural point of view, this is probably due to the pronounced differences in the ionic radii between K + and Ca 2+ (r K [6] : 1.38 Å, r Ca [6] : 1.00 Å). 10 Given that the compounds of the system K 2 O-CaO-SiO 2 can occur in a variety of residual materials, a comprehensive understanding of the equilibria between the existing phases is not only of interest for fundamental research, but also from an applicative point of view.…”

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K₄CaSi₆O₁₅—Solving a 90‐year‐old riddle

et al. 2021

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Polycrystalline K 4 CaSi 6 O 15 was prepared from (i) solid-state reactions between stoichiometric mixtures of the corresponding oxides/carbonates and (ii) combustion solution synthesis using Kand Ca-nitrates, tetraethyl orthosilicate (TEOS) and glycine (fuel component) as starting reagents.The compound was characterized by powder X-ray diffraction. Differential thermal analysis indicated that K 4 CaSi 6 O 15 melts congruently at about 956 °C. On cooling down from the liquid state, a distinct glass-forming tendency was observed. Single-crystals suitable for further structural investigations were obtained from sinter experiments just below the melting point.Basic crystallographic data are as follows: monoclinic symmetry, space group P c, a = 6.9299(2) Å,

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“…During the last years new research activities on this system were stimulated by investigations showing that potassium calcium silicates can occur in several types of residual materials such as steelmaking slags, ashes from biomass combustion or fertilizers produced from the residues of oil-shale industry (see, for example, 12 and references cited therein). In the course of a large series of synthesis experiments and subsequent chemical, structural and spectroscopic characterizations our group was able to show that (i) some of the phases mentioned by Morey et al 11 actually do exist; 13,14 (ii) some have slightly different chemical compositions; 15,16 (iii) a larger number of crystalline compounds have been overlooked in the previous study; [17][18][19] and (iv) at least one compound has to be discredited. 12 the proof of existence triggered the determination of their phase fields only very recently.…”

Section: Introductionmentioning

confidence: 88%

K₂CaSi₄O₁₀: A novel phase in the ternary system K₂O–CaO–SiO₂ and member of the litidionite group of crystal structures

2017

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The main goal of this work was to verify whether a phase with composition K2CaSi4O10 exists in the ternary system K2O‐CaO‐SiO2. Therefore, a series of solid‐state reactions of stoichiometric mixtures of K2CO3, CaCO3 and SiO2 was performed at 800 and 900?C which, indeed, resulted in the formation of this previously unknown potassium calcium silicate. More detailed characterizations of this compound were based on single‐crystal X‐ray diffraction experiments. Basic crystallographic data are as follows: triclinic symmetry, space group P‐1, a = 7.0915(7) Å, b = 8.4211(9) Å, c = 10.2779(12) Å, α = 104.491(10)°, β = 100.570(9)°, γ = 113.738(9)°, V = 515.26(10) Å3, Z = 2. Structure solution was performed by direct methods. Subsequent refinement calculations using anisotropic displacement parameters for all atoms converged to a residual of R(|F|) = 0.0355 for 1889 independent reflections with I > 2σ(I). From a structural point of view K2CaSi4O10 belongs to the so‐called litidionite family of A′AMSi4O10 compounds for which several natural and synthetic representatives have been described in the literature. Actually, it is the first member where the A′‐ and A‐positions are exclusively occupied by K‐ions. Following the nomenclature for oxosilicates K2CaSi4O10 can be allocated to the group of the tubular chain silicates. Fundamental building units are loop‐branched dreier double chains (running parallel to [100]) which can be described using the following structural formula: {lB,2∞1}[3Si8O20]. Ca‐ions are coordinated by 5 nearest oxygen neighbors in form of distorted trigonal bipyramids. By sharing a common edge two adjacent bipyramids are linked into [Ca2O8]‐dimers providing linkage between consecutive tubes in the direction of the c‐axis. Charge compensation is achieved by the incorporation of the larger potassium ions into cavities of the heteropolyhedral network. Powder X‐ray diffraction patterns of the bulk material of the synthesis products revealed that, additionally to K2CaSi4O10, the 800°C ‐sample contained K8CaSi10O25 and at least one further, yet unknown crystalline phase. This unidentified so‐called 22‐Å compound was also present in the 900 °C‐specimen together with K2CaSi4O10 and K2Ca4Si8O21. Our proof of existence of K2CaSi4O10 is a further step towards a better understanding of the ternary system K2O‐CaO‐SiO2 and provides a basis for identification and quantification of this compound in phase analysis. It corrects earlier phase‐analytical studies on this system which is of relevance for applied and technical mineralogy including different types of residual materials such as slags or ashes from biomass combustion. The results of our investigation show that even comparatively simple ternary oxide systems are not as well understood as expected.

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On the ambient pressure polymorph of K2Ca3Si3O10—An unusual mixed-anion silicate and its structural and spectroscopic characterization

Cited by 15 publications

References 31 publications

Phase equilibria and liquid phase behavior of the K2O-CaO-SiO2 system for entrained flow biomass gasification

Phase equilibria and liquid phase behavior of the K2O-CaO-SiO2 system for entrained flow biomass gasification

K₄CaSi₆O₁₅—Solving a 90‐year‐old riddle

K₂CaSi₄O₁₀: A novel phase in the ternary system K₂O–CaO–SiO₂ and member of the litidionite group of crystal structures

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On the ambient pressure polymorph of K2Ca3Si3O10—An unusual mixed-anion silicate and its structural and spectroscopic characterization

Cited by 15 publications

References 31 publications

Phase equilibria and liquid phase behavior of the K2O-CaO-SiO2 system for entrained flow biomass gasification

Phase equilibria and liquid phase behavior of the K2O-CaO-SiO2 system for entrained flow biomass gasification

K4CaSi6O15—Solving a 90‐year‐old riddle

K2CaSi4O10: A novel phase in the ternary system K2O–CaO–SiO2 and member of the litidionite group of crystal structures

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K₄CaSi₆O₁₅—Solving a 90‐year‐old riddle

K₂CaSi₄O₁₀: A novel phase in the ternary system K₂O–CaO–SiO₂ and member of the litidionite group of crystal structures