The Structures of Anhydrous Silver Sodalite Ag3[Al3Si3O12] at 298, 623, and 723 K from Rietveld Refinements of X-Ray Powder Diffraction Data: Mechanism of Thermal Expansion and of the Phase Transition at 678 K

Behrens, Peter; Kempa, P. B.; Assmann, Stefanie; Wiebcke, Michael; Felsche, J.

doi:10.1006/jssc.1995.1101

Cited by 15 publications

(16 citation statements)

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“…Furthermore, the temperature dependence of the intensity of the (2,1,1) reflection in the region 614 to 624 K is in accordance with a second-order transition. Therefore, our results indicate that the cubic to T2 transition is of second order, with the transition temperature ¹ +624 K. On further reducing the temperature below ¹ , the value of the order parameter increases, according to the increase of the intensity of the (2, 1, 1) reflection (Fig.…”

Section: Nature Of the Phase Transitionssupporting

confidence: 60%

“…This variation can be explained by normal thermal expansion (expansion coefficient 2.3;10\ K\). However, it should be noted that the simultaneous decrease of a and increase of c is compensated to a large extent for this reflection, and that the scattering angle of the (2,1,1) reflection is independent of the spontaneous strain. The intensity of this reflection varied between its maximum value, attained in the tetragonal phase below ¹"598 K, and zero in the cubic phase above ¹"624 K. Noteworthy is that the square of the intensity varies linearly with temperature, with a crossover between two different temperature coefficients at about 608 K (Fig.…”

Section: Methodsmentioning

confidence: 96%

“…Phase transitions may occur connected to structural distortions of the framework (1,2). Alternatively, for the subfamily of aluminate sodalites with ¹"Al and with X replaced by XO (X"S, Cr, Mo, W), phase transitions are possible related to rotational order-disorder of the anions.…”

Section: Introductionmentioning

confidence: 97%

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Structural Characterization of the High-Temperature Phase Transitions in Ca8[Al12O24](MoO4)2Aluminate Sodalite Using X-ray Powder Diffraction

Smaalen

Dinnebiér

Katzke

et al. 1997

Journal of Solid State Chemistry

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Section: Nature Of the Phase Transitionssupporting

confidence: 60%

Section: Methodsmentioning

confidence: 96%

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Structural Characterization of the High-Temperature Phase Transitions in Ca8[Al12O24](MoO4)2Aluminate Sodalite Using X-ray Powder Diffraction

Smaalen

Dinnebiér

Katzke

et al. 1997

Journal of Solid State Chemistry

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“…Zeolite A samples into which PbI 2 had been inserted showed blue shifts in their UV/visible adsorption edges that depended on the degree of PbI 2 loading. [7] As part of our investigations into the synthesis, structure and properties of aluminosilicate sodalites containing soft metal cations, [8,9] we have studied the ion exchange of the three well-characterized sodium hydro sodalites, [Na 3 Here we report primarily the characterization of this lead hydro sodalite by means of Rietveld structure refinement based on powder X-ray diffraction data and 1 H MAS NMR, FTIR, and XANES (X-ray adsorption near-edge structure) spectroscopy. Full details of the ion-exchange behavior will be presented elsewhere, along with the ion-exchange characteristics of other soft metal cations with sodium hydro sodalites.…”

Section: Introductionmentioning

confidence: 99%

Lead Hydro Sodalite [Pb2(OH)(H2O)3]2[Al3Si3O12]2: Synthesis and Structure Determination by Combining X-ray Rietveld Refinement,1H MAS NMR FTIR and XANES Spectroscopy

et al. 2000

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Ion exchange of the sodium hydro sodalites [Na3(H2O)4]2-[Al3Si3O12]2 [Na4(H3O2)]2[Al3Si3O12]2 and [Na4(OH)]2[Al3Si3O12]2 with aqueous Pb(NO3)2 solutions yielded, whichever reactant sodalite phase was used, the same lead hydro sodalite, [Pb2(OH)-(H2O)3]2[Al3Si3O12]2. Thus, in the case of the non-basic reactant [Na3(H2O)4]2-[Al3Si3O12]2 an overexchange occurs with respect to the number of nonframework cationic charges. Rietveld structure refinement of the lead hydro sodalite based on powder X-ray diffraction data (cubic, a = 9.070 A, room temperature, space group P43n) revealed that the two lead cations within each polyhedral sodalite cage form an orientationally disordered dinuclear [Pb2(micro-OH)(micro-H2O)(H2O)2]3+ complex. Due to additional lead framework oxygen bonds the coordination environment of each metal cation (CN 3+3) is approximately spherical, and clearly the lead 6s electron lone pair is stereochemically inactive. This is also suggested by the absence of a small peak at 13.025 keV, attributed in other Pb2+-O compounds to an electronic 2p-6s transition, in the PbL3 edge XANES spectrum. 1H MAS NMR and FTIR spectra show that the hydrogen atoms of the aqua hydroxo complex (which could not be determined in the Rietveld analysis) are involved in hydrogen bonds of various strengths.

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“…8d) to 7.8° at 623 K (Fig. 8e), as evidenced by Rietveld refinements of x-ray powder diffraction data (BEHRENs et al 1992a). At 673 K, near to the fully expanded state with cp = 0°, a phase transition takes place because a further unfolding of the framework by reducing cp is not possible anymore (BEHRENS et al 1992a).…”

Section: Framework Mechanics and Effective Pore Sizesmentioning

confidence: 89%

Pores in Tetrahedral Frameworks

Behrens

1993

Multifunctional Mesoporous Inorganic Solids

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ABSTRACT. Porous crystalline tetrahedral frameworks, i.e. zeolites and related compounds, are the most important class of microporous substances due to their uniform pore size, the periodic arrangement of pores and to the fact that the framework structure and chemistry can be controlled rather deliberately. Numerous attempts to extend the favourable characteristics of these compounds to the mesoporous regime have failed so far. This article deals with the factors influencing the size and the shape of the pores in zeolite-type compounds. The primary factor is the kind of linking of [T041:J tetrahedra determining mainly the size and shape of the windows and cavities. This topological aspect of the structure of tetrahedral frameworks is discussed in the first part of the article. On that basis, topological and other concepts to extend the apertures of periodic structures with well-defined uniform pores into the mesoporous range are discussed in the second part. The third section of this article focusses on "framework mechanics". It has often been realized that the pore sizes of zeolite-type compounds as determined from absorption and diffusion experiments differ from those estimated on the basis of the crystal structure. It will be shown that the conformation of the framework -as determined by its dynamic response on temperature and pressure changes and by its adaption to the spatial and coordinative demands of the guest species -strongly influences the "real" size and shape of the pores and thus their effective apertures.

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The Structures of Anhydrous Silver Sodalite Ag3[Al3Si3O12] at 298, 623, and 723 K from Rietveld Refinements of X-Ray Powder Diffraction Data: Mechanism of Thermal Expansion and of the Phase Transition at 678 K

Cited by 15 publications

References 0 publications

Structural Characterization of the High-Temperature Phase Transitions in Ca8[Al12O24](MoO4)2Aluminate Sodalite Using X-ray Powder Diffraction

Structural Characterization of the High-Temperature Phase Transitions in Ca8[Al12O24](MoO4)2Aluminate Sodalite Using X-ray Powder Diffraction

Lead Hydro Sodalite [Pb2(OH)(H2O)3]2[Al3Si3O12]2: Synthesis and Structure Determination by Combining X-ray Rietveld Refinement,1H MAS NMR FTIR and XANES Spectroscopy

Pores in Tetrahedral Frameworks

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