JAST
2012 March;3(1):95-103.
Published online 2012 January 17.
doi:http://dx.doi.org/10.5355/JAST.2012.95
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| Copyright ⓒ 2010 Journal of Analytical Science & Technology |
| Synthesis and characterization of perchlorate enclathrated aluminogermanate sodalite and its potassium and silver derivatives |
| Ashok Vishram Borhade*, Arun Gabaji Dholi, Dipak Ramrao Tope, Sanjay Gauram Wakchaure |
| Research Centre and Department of Chemistry, HPT Arts and RYK Science College, Nasik 422005, India |
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Corresponding Author:
Ashok Borhade ,Tel: O9421831839, Email: ashokborhade2007@yahoo.co.in |
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ABSTRACT |
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| Perchlorate enclathrated sodalite with aluminogermanate host framework has been obtained from low temperature hydrothermal synthesis at 373K. In addition mixed sodium, potassium and silver perchlorate sodalite is obtained by aqueous cation exchange method. The crystal structure of Na8[AlGeO4]6(ClO4)2, Na3.2K4.8[AlGeO4]6(ClO4)2 and Na3.9Ag4.1[AlGeO4]6(ClO4)2 sodalites were refined from X-ray powder data in the space group P 3n: a = 9.249 Å, V = 791.35 Å, Rwp = 0.2230, Rp = 0.1609 and Al-O-Ge angle is 140.930o and a = 9.257 Å, V = 793.28 Å, Rwp = 0.1596, Rp = 0.1180 and Al-O-Ge angle is 141.080o, a = 9.195 Å, V = 775.95 Å, Rwp = 0.2211, Rp = 0.1662 and Al-O-Ge angle is 139.034o ,respectively. The 27Al MAS NMR study confirms alternating Ge and Al ordering of sodalite framework, while 23Na give insights into the structure and dynamics of the cage fillings. The recorded Infrared and Raman spectra show absorption band typical for the sodalite structure. Thermogravimetric analysis has provided information on the extent of perchlorate entrapment, stability within the sodalite cage and decomposition properties. SEM study shows the retention of cubical morphology of the sodalite derivatives.
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| Keywords: Hydrothermal method, Aluminogermanate sodalite, Cation exchange, IR shift, Rietveld refinement, MAS NMR |
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Introduction |
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The aluminogermanate framework of the sodalite structure formed by the space-filling array of [46 68] polyhedral cages [1,2], the so called β-cages, can be regarded as a non porous matrix with well defined opening for the enclathration of guest molecules. Their use as non composites in non linear optics or for host matrix of semiconductor quantum super lattices. The common sodalite stoichiometry can be represented by Na8[AlGeO4]6(X2); X is a central monovalent negative ions such as OH-, Cl-, Br-, I-, ClO4- --- etc [3-6].
Sodalites are unique due to the presence of guest anions. Aluminogermanate sodalites can be synthesized using a variety of routes, including low temperature condensation reaction in strong alkali solution [7], solid state sintering [8] and hydrothermal synthesis [6, 9-13]. Many anions have been encapsulated using these techniques. In present study we report synthesis and characterization of sodalite of Na8[AlGeO4]6(ClO4)2 and its potassium and silver derivatives. As part of our investigation into synthesis, structure and properties of aluminogermanate sodalite containing ClO4- anion, we have studied the ion exchange of well characterized sodium perchlorate sodalite with aqueous AgNO3 solution. This paper reports the characterization of Na8[AlGeO4]6(ClO4)2, Na3.2K4.8[AlGeO4]6(ClO4)2 and Na3.9Ag4.1[AlGeO4]6(ClO4)2 by means of a Rietveld structure refinement based on powder X-ray diffraction, FT-IR, Raman, and by Thermal analysis. In this paper we have gained further, insight into these materials through the use of magic angle spinning (MAS) NMR spectroscopy. |
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Materials and Methods |
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Synthesis
Synthesis of aluminogermanate perchlorate sodalite Na8[AlGeO4]6(ClO4)2 have been achieved by low temperature hydrothermal technique, germanium oxide (source of germanium) and sodium hydroxide solution was taken in Teflon autoclave (A). This reaction mixture was shaken for 5 minutes and kept in an oven at 373K for few minutes. In another Teflon bottle (B) containing NaAlO2 (source of aluminum) along with sodium hydroxide was kept in an oven at 373K for 5 minutes. The hot solutions of A and B were mixed rapidly and excess NaClO4 is added. A gel formed with molar composition of 1 GeO2: 1NaAlO2: 4 NaOH: 6 NaClO4 respectively, shaken vigorously for another 5 minutes and the mixture kept at 373 K for five days in a Teflon autoclave. The white, microcrystalline product was filtered, washed with deionized water and dried overnight at 373K. Further, ion exchange [14] was performed by treating the powder of sodalite with a solution of a metal salt for period of 24 h at 373K in Teflon autoclave. The potassium was determined by flame photometry of the exchange solution (Na+ content of the solution after exchange reaction) and silver content by Volhard method.
Spectroscopy
IR absorption analysis (KBr pellets) was performed on a Shimadzu, 8400-S FT spectrometer in the range of 4000 to 400 cm-1. Further Raman spectra in the range 2000 to 200 cm-1 were recorded at room temperature using Nicolet almega XR-dispersive Raman Spectrophotometer (Thermo Electron Corporation) with 780 nm Laser. The sample containing disk was rotated during excitation to minimize heating effects.
X-ray powder diffraction pattern for synthesized sodalites were collected using a Philips PW-1710 operating at 25 kV and 25 mA using Cu-Kα radiation with wavelength λ=1.54 Å. The powder diffractometer of these materials were recorded within span of angles between 10-90o at 298 K. The sample was evaluated using a step size 0.017o. The characterization of sodalites was performed by X-ray powder diffraction method using Rietveld refinement GSAS program. The 27Al and 23Na MAS NMR spectra were recorded at 130.0 MHz on a Bruker Advance 500 MHz wide bore spectrometer with 6.15 μsec pulse duration, 3 sec pulse delay and a spinning rate of 5 KHz in a 2.5 mm probe (alumina and NaCl are internal standard respectively).
Studies by scanning electron microscopy (SEM) were carried out to provide information about the particle morphology and crystal growth mechanism. The SEM was taken with the help of JEOL JEM-6360A model equipped with JEOL JEC 560 auto carbon coater. Simultaneous thermal analyses, TGA-DTA, were carried out in argon with a Mettler Thrmoanalyzer 146 with heating 20 oC / min in the range of 298 -1273 K. The filling of sodalite cages with the perchlorate anion was checked by thermogravimetry. |
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Results and Discussion |
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IR Spectroscopy
Infrared spectra were obtained for Na8[AlGeO4]6(ClO4)2, Na3.2K4.8[AlGeO4]6(ClO4)2 and Na3.9Ag4.1[AlGeO4]6(ClO4)2 sodalites in the region of 4000-400 cm-1 are depicted in (Fig.1) and the different frequencies obtained are listed in Table 1. In the mid-infrared region the symmetric and unsymmetrical T-O-T vibrations of the sodalite framework appear. Henderson and Taylor [15] already showed the dependence of framework expansion on the positions of symmetric and asymmetric T-O-T modes. In aluminogermanate sodalite one asymmetric stretching at 850 cm-1, two mode for symmetric stretching at 600 cm-1, and bending mode is visible in far IR at 380 cm-1[6,16].
In our synthesized aluminogermanate sodalite products, the framework band appears at 873.94, 617 and 592 cm-1 for pure sodium sodalite. In potassium exchanged sodalite the frame work band appears at 873.94, 617, and 592 cm-1. Wavenumber at 871.80, 617.22 and 580 cm-1 in silver exchanged sodalite. Some of weak bands at about 3500 cm-1 correspond to the amount of OH-, which is found as an impurities arising from the hydrothermal process of crystallization. The enclathrated guests can be detected according to their intensive absorptions band for perchlorate at 1112 cm-1. The absorption band at 620 cm-1 is also characteristic for the enclathration of perchlorate in the sodalite cages. Potassium and silver exchanged sodalite, the asymmetric vibration υa for ClO4-, found at 1114cm-1 and 1108 cm-1 respectively. This shift in IR frequency as a function of cation exchange is explained on the basis of cell constant. The silver containing sodalite have slightly smaller cell constant than the corresponding sodium and potassium sodalite [17].
Raman Spectroscopy
Raman spectra recorded for Na8[AlGeO4]6(ClO4)2, Na3.2K4.8[AlGeO4]6(ClO4)2 and Na3.9Ag4.1[AlGeO4]6 (ClO4)2, sodalites in the region of 2000-200 cm-1 are shown in (Fig.2). One of the advantages of Raman is the framework vibrations are weak and the frequency for enclathrated species are clearly visible. υ1, υ2, υ3 and υ4 modes of ClO4- vibrations are clearly visible in spectra ((Fig.2) a, b and c ).
The absorption band at 1102.92, 1090 cm-1 is due to ClO4- in sodium and potassium sodalite (Table 1). The expected frequency for AgClO4-SOD is obscured due to higher back scattering and is much weaker for the synthesized sodalite. The position of tetrahedral υ3 of ClO4- vibration is seen to move smoothly from 1116.82 cm-1 in NaClO4 - SOD to 1102.0 cm-1 in silver exchanged sodalite, this may indicate some compression of the ClO4- groups in NaClO4.
Structure refinement
The refinement of parent aluminogermanate sodalite is performed on considering aluminosilicate perchlorate as a starting model. The refinement of potassium and silver derivatives also performed on considering respective aluminosilicate perchlorate as a starting model. The crystallographic data and experimental conditions for the structure refinement of perchlorate aluminogermanate sodalite are given in Table 2. The aluminium and germanium were placed on 6 (c) (1/4, 0, 1/2) and 6(d) (1/4, 1/2, 0) sites respectively, chlorine on the 2(a) (0, 0, 0) site centre and the four oxygen at 24i position of the space group P43n. Initially, the sodium and potassium or silver were placed on 8(e) (x, x, x) site, x≈ 0.2141, after refinement sodium and potassium or silver found to occupy separate positions. The final positional parameters are given in Table 3. The selected bond distances and bond angles for sodium, potassium and silver sodalites are summarized in Table 4. The Rietveld plot of these aluminogermanate sodalites synthesized with an ideal composition Na8[AlGeO4]6(ClO4)2, Na3.2K4.8[AlGeO4]6(ClO4)2 and Na3.9Ag4.1[AlGeO4]6(ClO4)2 are shown in (Fig.3) (a, b and c). For the Na-Sod a = 9.249 Å, V = 791.35 Å, Rwp = 0.2230, Rp = 0.1609 and Al-O-Ge angle is 140.930o and a = 9.257 Å, V = 793.28 Å, Rwp = 0.1596, Rp = 0.1180 and Al-O-Ge angle is 141.080o, a = 9.195 Å, V = 775.95 Å, Rwp = 0.2211, Rp = 0.1662 and Al-O-Ge angle is 139.034o respectively. The refinement was performed on arranging chloride at the centre and the four oxygen at 24i position of the space group P43n. Average of typical Al-O and Ge-O distances in tetrahedral environments (Al-O 1.7613 Å and Ge-O 1.7516 Å). The calculated bond distances within the anions of sodalite is somewhat distorted in sodium sodalite the Cl-O distance is 1.564 Å, 1.369 Å for potassium sodalite and 1.451 Å in silver sodalite as compared to 1.44Å in perchlorate salt. The central anion was found to be highly disordered orientations of the tetrahedral XO4 group [18]. The possible geometry of the sodalite structure (Fig.4) is very stable, symmetric aluminogermanate framework. ClO4- anion is encapsulated in the framework, chlorine atom is at the centre of the cage.
MAS NMR spectroscopy
Specific investigations of the host-framework or of the guest species of sodalites can be performed by the
selection of the appropriate atomic nuclei for the NMR experiments. 27Al NMR is particularly useful in the characterization of the framework structure. 23Na NMR provides information on the guest species located in the sodalite cages. The 27Al MAS NMR spectra (Fig.5) of aluminogermanate sodalites containing perchlorate guest molecules exhibit a single line for Al(OGe)4 environments, confirming alternating Ge, Al ordering and cubic symmetry of the sodalite framework. The chemical shifts are observed at 67.395, 67.233, and 68.786 ppm for sodium, potassium and silver sodalites respectively. It should be noted that the splitting into lines reported for aluminosilicate sodalite by M.T. Weller et al.[19], it is not observed in our sodalite sample. 27Al has I =5/2, i.e. possesses a nuclear quadrupole moment, and is, therefore, involved in quadrupole interactions if the local charge distribution around the Al nucleus deviates from spherical symmetry.
23Na NMR provides information on the guest species enclathrated in sodalite cage. The quadrupole interactions are determined by the charge distribution around the sodium ion, i.e. preferably by the effective charge and geometrical arrangement of the atoms in the first coordination shell of Na. In sodalites the sodium cations are located above the center of the six-ring windows of the cages and are coordinated to three oxygen atoms of these rings. Additional coordinative bonds are formed to distinct coordination sites of the anions present in the sodalite cages. Thus deviations from centrosymmetrical charge distribution around the sodium ions and, therefore, specific quadrupole interactions may occurs giving rise characteristic quadrupolar line shapes in the 23Na MAS NMR spectra (Fig. 6) and are summarized in Table 5. The 23Na MAS NMR spectra of most of aluminosilicate sodalites exhibit a characteristic quadrupolar line shape [20]. This observation is also finds in our aluminogermanate perchlorate sodalites, which may be explained by a fast dynamic reorientation of the anions averaging the distinct chemical shifts and field gradients at the sodium sites. Two different sodium environments are at least present in these sodalite compositions which should give rise to different quadrupole interactions.
Thermal analysis
Analysis of TGA results for perchlorate sodalites allowed accurate determination of perchlorate content via thermal decomposition to the respective chloro sodalite. The simultaneous thermal analysis of Al-Ge perchlorate sodalite (Fig. 7 a, b and c) demonstrate the total loss of oxygen by the cage filling salt molecules within the range 848 K to 983 K for sodium and silver sodalite according to the decomposition reaction.
Above 1100 K the perchlorate sodalite starts to decompose to form a nepheline, which is typical for sodalite system. From the thermogravimetric analysis it is evident that at these temperatures the entire amount of NaCl escapes from sodalite cages. Quantitatively the degree of the cage filling by salt molecules can be calculated on the basis of both the oxygen and the NaCl loss [21]. DTA curves (Fig. 7 a, b and c) showing the decomposition reactions are exothermic in the sodalite structure.
From decomposition temperature and calculation’s in weight loss shows satisfactory results. For sodium perchlorate sodalite about 9.21 % weight loss gives 98.19 % cage filling with NaClO4. Potassium perchlorate sodalite about 8.422 % weight loss gives 95.7. % cage filling and 7.317 % weight loss gives 97.9 % cage filling in silver sodalite. The decomposition temperature is 873, 848 and 873 K for sodium, potassium and silver sodalite respectively. One of the explanations of this observed trend is the size of sodalite cage and interaction of cation with perchlorate anion [22].
The decomposition temperature of sodium perchlorate salt (NaClO4) is 743 K. The enclathrated sodalite salt starts decomposing at above 848 K, this clearly shows the thermal stability of different anions in sodalite framework and this property can be useful in preparation of thermally stable paints.
Crystal morphology
The information about the particle morphology and the macroscopic crystal growth for aluminogermanate sodalite synthesized are shown in Fig. 8 (a, b and c) as well as to determine the distribution of different cages throughout the lattice. Careful inspection of figures shows the surface of the crystal is smoother. Further, observation of SEM picture shows sharp edges with cubic crystal habit. |
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Conclusions |
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| It is possible to modify the sodalite cage by germanium substitution using low temperature hydrothermal method. The strong IR absorption band at 1112 cm-1 confirms the encapsulation of ClO4- in the sodalite structure during the synthesis. The ion exchange properties, stability, and extent of cage filling of different sodalite were also studied successfully. The Rietveld refinement provides important information about bond distances and bond angles of aluminogermanate sodalite. 27Al confirms alteration of Al and Ge in sodalite framework. The new type of sodalite synthesized shows cubic structure and SEM study confirms the cubic morphology. |
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Acknowledgement |
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| Authors are thankful to UGC, New Delhi, for financial support. AGD is thankful to research centre, HPT and RYK College, Nashik, and to Dr. A.V. Mahajan, Dept of physics IIT Mumbai for providing X-ray analysis. |
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FIGURES |
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Fig.1
IR absorption spectra of a) Na8[AlGeO4]6(ClO4)2, b) Na3.2K4.8[AlGeO4]6(ClO4)2, and c) Na3.9Ag4.1[AlGeO4]6(ClO4)2 sodalites. Sample is mixed with KBr and pallet is prepared. IR-transmission spectra of the aluminogermanate sodalites are obtained at room temperature. |
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Fig.2
Raman absorption spectra of a)Na8[AlGeO4]6(ClO4)2, b) Na3.2K4.8[AlGeO4]6(ClO4)2, c) Na3.9Ag4.1[AlGeO4]6(ClO4)2. Raman spectra of the perchlorate enclathrated sodalites taken at room temperature. The range is 200 cm-1to 800 cm-1 |
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Fig.3
Profile fit to powder X-ray data for a) Na8[AlGeO4]6(ClO4)2, b) Na3.2K4.8[AlGeO4]6(ClO4)2, and c) Na3.9Ag4.1[AlGeO4]6(ClO4)2. Full line is the difference and thick mark shows the reflection positions and difference curve below. |
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Fig.4
Schematic diagram of sodalite cage structure. The perchlorate ion is at the center of the cage. The solid lines represent the aluminogermanate cage. |
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Fig.5
27Al MAS NMR spectra of a) Na8[AlGeO4]6(ClO4)2, b) Na3.2K4.8[AlGeO4]6(ClO4)2, and c) Na3.9Ag4.1[AlGeO4]6(ClO4)2. The 27Al MAS NMR spectra of aluminogermanate sodalites significant shift due to potassium and silver cations.
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Fig.6
23Na MAS NMR spectra of a) Na8[AlGeO4]6(ClO4)2, b) Na3.2K4.8[AlGeO4]6(ClO4)2, and c) Na3.9Ag4.1[AlGeO4]6(ClO4)2. The 23Na MAS NMR spectra of aluminogermanate sodalites showing clear quadrupolar interaction due to non symmetrical environment in all three sodalites. Resonance shift is due to ion exchanged. |
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Fig.7
TGA and DTA of a) Na8[AlGeO4]6(ClO4)2, b) Na3.2K4.8[AlGeO4]6(ClO4)2, and c) Na3.9Ag4.1[AlGeO4]6(ClO4)2 sodalites. Thermal stability of perchlorate encapsulated in aluminogermanate sodalite cage and its decomposition temperature are higher than perchlorate salts is visible in thermogram. |
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Fig.8
SEM images of a) Na8[AlGeO4]6(ClO4)2, b) Na3.2K4.8[AlGeO4]6(ClO4)2, and c) Na3.9Ag4.1[AlGeO4]6(ClO4)2 sodalites. Cubical habits of sodalite and smooth surface are seen from aluminogermanate sodalite. After ion exchanged with potassium and silver the morphology is retained. |
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TABLES |
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Table.1
Mid IR spectral frequencies (cm-1) and Raman frequencies (cm-1) for the framework region and anion modes for perchlorate sodalites. |
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Table.2
Crystallographic data and experimental conditions for the structure refinement of perchlorate
aluminogermanate sodalite. |
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Table.3
Fractional coordinates and equivalent displacement
parameters of aluminogermanate perchlorate sodalites. |
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Table.4
Selected derived bond distances and bond angles for aluminogermanate perchlorate sodalites perchlorate sodalites. |
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Table.5
23Na and 27Al NMR data of sodium, potassium and silver aluminogermanate perchlorate sodalites. |
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REFERENCE |
|
|
| 1. |
Fischer, W.; Meier, M. Molecular Sieves; Society of chemical industry: London, 1968. |
| 2. |
Pauling, L. The structure of sodalite and helvite. Z. Kristallogr. 1930, 74, 213-225. |
| 3. |
Barrer, R. M.; Cole, J. F.; Villiger, H. Chemistry of soil minerals. Part VII. Synthesis, properties, and crystal structures of salt-filled cancrinites. J. Chem. Soc. A. 1970, 1523-1531. |
| 4. |
Hund, F. Nitrite, Cyanide, and Thiocyanate Sodalite. Z. Anorg. Allg. Chem. 1984, 511, 225-230. |
| 5. |
Felsche, J.; Luger, S. Phases and thermal decomposition characteristics of Na6+x[AlSiO4]6(OH)x.nH2O. Thermochim. Acta. 1987, 118, 35-55. |
| 6. |
Buhl, J-Ch.; Murshed, M. M. (Na4BH4)3+ guests inside aluminosilicate, gallosilicate and aluminogermanate sodalite host frameworks studied by 1H, 11B, and 23Na MAS NMR spectroscopy. Mater. Res. Bulle. 2009, 44, 1581-1585. |
|
 |
| 7. |
Barrer, R. M.; Cole, J. F. Interaction of sodium vapour with synthetic sodalite: sorption and formation of colour centres. J. Phys. Chem. Solids. 1968, 29, 1755-1758. |
|
|
| 8. |
Schipper, P. J.; VanDoorn, C. Z.; Bolwijn, P. T. Preparation of cathodochromic sodalites. J. Am. Cera. Soc. 1972, 55, 256-259. |
| 9. |
Dyer, A. An Introduction to Zeolite Molecular Sieves, John wiley & Sons, New York, 1988. |
| 10. |
Barrer, R. M. Zeolites and Clay Minerals as Sorbents and Molecular Sives, Academic press, New York, 1978. |
| 11. |
Barrer, R. M. Hydrothermal Chemistry of Zeolites, Academic Press, London, 1982. |
|
|
| 12. |
Johnson, G. M.; Mead, P. J.; Weller, M. T. Structural trends in the sodalite family. Phys. Chem. Chem. Phys.1999, 1, 3709-3714. |
|
|
| 13. |
Johnson, G. M.; Mead, P. J.; Weller, M. T. Synthesis of a range of anion-containing gallium and germanium sodalites. Micro and Meso. Mate. 2000, 38, 445-460. |
| 14. |
Eiden-Assmann, S. New heavy metal-hydro-sodalites containing Cd2+, Ag+ or Pb2+: synthesis by ion exchange and characterization. Mater. Res. Bulle. 2002, 37, 875-889. |
| 15. |
Henderson, C. M. B.; Taylor, D. Infrared spectra of aluminogermanate- and aluminate-sodalites and a re-examination of the relationship between T-O bond length, T-O-T angle and the position of the main i.r. absorption band for compounds with framework structures. Spectrochimica Acta Part A: Molecular Spectroscopy. 1979, 35, 929-635. |
|
|
| 16. |
Buhl, J-Ch.; Gesing, T. M.; Hofs, T.; Ruscher, C. H. Synthesis and crystal Structure of gallosilicate and aluminogermanate tetrahydroborate sodalites Na8[GaSiO4]6(BH4)2 and Na8[AlGeO4]6(BH4)2. J. Solid State Chem. 2006, 179, 3877-3882. |
| 17. |
Stein, A.; Ozin, G. A.; Mecdonald, P. M.; Stucky, G. D.; Jelinek, R. Silver, sodium halosodalites: class A sodalites. J. Am. Chem. Soc.1992, 114, 5171-5186. |
|
|
| 18. |
Brenchley, M. E.; Weller, M. T. Synthesis and structures of M8[AlSiO4]6(ClO4)2, M= Na, Li, K; X=Cl, Mn sodalites. Zeolites. 1994, 14, 682-686. |
| 19. |
Weller, M. T.; Brenchley, M. E.; Apperley, D. C.; Davies, N. A. Correlations between 27Al magic-angle spinning nuclear magnetic resonance spectra and the coordination geometry of framework aluminates. Solid Stat. Nucl. Magn. Reson. 1994, 3, 103-106. |
|
 |
| 20. |
Engelhardt, G.; Sieger, P.; Felsche, J. Multinuclear solid state NMR of host-guest systems with TO, (T = Si, Al) host-frameworks. A case study on sodalites, Analytica Chimica Acta. 1993, 283, 967-985. |
|
|
| 21. |
Hackbarth, K.; Gesing, T. M.; Fechtelkord, M.; Stief, F.; Buhl, J-Ch. Synthesis and crystal structure of carbonate cancrinite Na8[AlSiO4]6CO3(H2O)3.4, Grown under low-temperature hydrothermal conditions. Micro and Meso. Mate. 1999, 30, 347-358. |
|
|
| 22. |
Kendrick, E.; Dann, S. Synthesis, properties and structure of ion exchanged hydrosodalite. J. Solid State Chem. 2004, 177, 1513-1519. |
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