Phillipsite, a common natural zeolite with ideal composition K2(Na,Ca0.5)3[Al5Si11O32]• 12H2O, is typically found in amygdaloidal vugs of massive volcanic rocks (e.g. basalt, leucitites), in palagonnitic basalts and tuffs as an alteration product of volcanic glass, or in diagenetically altered sediments in “closed hydrologic systems” (e.g. saline lake and hot spring deposits) and “open hydrologic systems” (e.g. soils and land surface deposits, burial diageneic environments, deep-sea sediments). Phillipsite is isotypic with harmotone [Ba2(Na,Ca0.5)Al5Si11O32•12H2O], forming a continuous series with no compositional gap. Crystals of natural phillipsite are often found in spherical radial aggregates and ubiquitously twinned (cruciform single and double penetration twins on {001}, {021}, and {110}). Intergrowths with several other zeolites (e.g. faujasite, offretite, gismondine, garronite and gobbinsite) have been reported The crystal structure, crystal chemistry and low-temperature behavior of a natural phillipsite-Na from the “Newer Volcanic Suite”, Richmond, Melbourne district, Victoria, Australia [K0.75(Na0.88Ca0.57)=1.45(Al2.96Ti0.01Si5.07)=8.04O16•6.2H2O (Z=2), a=9.9238(6), b=14.3145(5), c=8.7416(5)Å, = 124.920(9)° and V=1018.20(9)Å3, space group P21/m], have been investigated by means of in-situ single-crystal X-ray diffraction, thermogravimetric analysis and electron microprobe analysis in the wavelength dispersive mode. Two accurate structural refinements have been obtained on the basis of single-crystal X-ray diffraction data collected at 298 and 100 K, with: R1(F)298K=0.035, 3678 unique reflections with FO>4(FO) and 195 parameters, and R1(F)100K=0.035, 3855 unique reflections, FO>4(FO) and 195 parameters. In both refinements the residuals in the final difference Fourier maps are less than 1e-Å-3. A configuration of the extra-framework population different from that reported in previous studies is found at room temperature, with two possible sites for potassium (K1 and K2), one sodium/calcium-site (Ca) and seven independent sites partially occupied by water molecules (W1, W2, W3, W4, W4’, W5 and W6). The low-temperature refinement shows that the framework component of the phillipsite structure is maintained within the T-range investigated. However, a change in the configuration of the extra-framework content occurs at low temperature: the occupancy of site K2 drastically decreases, while that of site K1 increases, the Ca-site is split into two sub-sites (Ca1 and Ca2) and the number of water molecule sites decreases to six (W1, W2, W3, W4, W5 and W6). The evolution of the unit-cell parameters with T (measured at 298, 250, 200, 150 and 100 K) shows a continuous and linear trend, without evident thermo-elastic anomalies. The axial and volume thermal expansion coefficients (αj = lj-1lj/T , αV = V-1V/T) between 100 and 298 K, calculated by weighted linear regression, yield the following values: αa = 1.8(1)•10-5, αb = 1.2(1)•10-5, αc = 1.1(1)•10-5 and αV = 3.7(1)•10-5K-1. The thermal expansion of phillipsite is significantly anisotropic (αa:αb:αc = 1.64 : 1.09 : 1).

NEW INSIGHTS INTO THE CRYSTAL STRUCTURE AND CRYSTAL CHEMISTRY OF THE ZEOLITE PHILLIPSITE-Na / G.D. Gatta, P. Cappelletti, N. Rotiroti, R. Rinaldi, C. Slebodnick. ((Intervento presentato al 1. convegno SIMP-AIC Joint Meeting "Learning from and for the Planet Earth" tenutosi a Sestri Levante nel 2008.

NEW INSIGHTS INTO THE CRYSTAL STRUCTURE AND CRYSTAL CHEMISTRY OF THE ZEOLITE PHILLIPSITE-Na

G.D. Gatta;N. Rotiroti;
2008

Abstract

Phillipsite, a common natural zeolite with ideal composition K2(Na,Ca0.5)3[Al5Si11O32]• 12H2O, is typically found in amygdaloidal vugs of massive volcanic rocks (e.g. basalt, leucitites), in palagonnitic basalts and tuffs as an alteration product of volcanic glass, or in diagenetically altered sediments in “closed hydrologic systems” (e.g. saline lake and hot spring deposits) and “open hydrologic systems” (e.g. soils and land surface deposits, burial diageneic environments, deep-sea sediments). Phillipsite is isotypic with harmotone [Ba2(Na,Ca0.5)Al5Si11O32•12H2O], forming a continuous series with no compositional gap. Crystals of natural phillipsite are often found in spherical radial aggregates and ubiquitously twinned (cruciform single and double penetration twins on {001}, {021}, and {110}). Intergrowths with several other zeolites (e.g. faujasite, offretite, gismondine, garronite and gobbinsite) have been reported The crystal structure, crystal chemistry and low-temperature behavior of a natural phillipsite-Na from the “Newer Volcanic Suite”, Richmond, Melbourne district, Victoria, Australia [K0.75(Na0.88Ca0.57)=1.45(Al2.96Ti0.01Si5.07)=8.04O16•6.2H2O (Z=2), a=9.9238(6), b=14.3145(5), c=8.7416(5)Å, = 124.920(9)° and V=1018.20(9)Å3, space group P21/m], have been investigated by means of in-situ single-crystal X-ray diffraction, thermogravimetric analysis and electron microprobe analysis in the wavelength dispersive mode. Two accurate structural refinements have been obtained on the basis of single-crystal X-ray diffraction data collected at 298 and 100 K, with: R1(F)298K=0.035, 3678 unique reflections with FO>4(FO) and 195 parameters, and R1(F)100K=0.035, 3855 unique reflections, FO>4(FO) and 195 parameters. In both refinements the residuals in the final difference Fourier maps are less than 1e-Å-3. A configuration of the extra-framework population different from that reported in previous studies is found at room temperature, with two possible sites for potassium (K1 and K2), one sodium/calcium-site (Ca) and seven independent sites partially occupied by water molecules (W1, W2, W3, W4, W4’, W5 and W6). The low-temperature refinement shows that the framework component of the phillipsite structure is maintained within the T-range investigated. However, a change in the configuration of the extra-framework content occurs at low temperature: the occupancy of site K2 drastically decreases, while that of site K1 increases, the Ca-site is split into two sub-sites (Ca1 and Ca2) and the number of water molecule sites decreases to six (W1, W2, W3, W4, W5 and W6). The evolution of the unit-cell parameters with T (measured at 298, 250, 200, 150 and 100 K) shows a continuous and linear trend, without evident thermo-elastic anomalies. The axial and volume thermal expansion coefficients (αj = lj-1lj/T , αV = V-1V/T) between 100 and 298 K, calculated by weighted linear regression, yield the following values: αa = 1.8(1)•10-5, αb = 1.2(1)•10-5, αc = 1.1(1)•10-5 and αV = 3.7(1)•10-5K-1. The thermal expansion of phillipsite is significantly anisotropic (αa:αb:αc = 1.64 : 1.09 : 1).
set-2008
Zeolite, phillipsite, X-ray diffraction
Settore GEO/09 - Georisorse Miner.Appl.Mineral.-Petrogr.per l'amb.e i Beni Cul
NEW INSIGHTS INTO THE CRYSTAL STRUCTURE AND CRYSTAL CHEMISTRY OF THE ZEOLITE PHILLIPSITE-Na / G.D. Gatta, P. Cappelletti, N. Rotiroti, R. Rinaldi, C. Slebodnick. ((Intervento presentato al 1. convegno SIMP-AIC Joint Meeting "Learning from and for the Planet Earth" tenutosi a Sestri Levante nel 2008.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/49219
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