A powder diffraction study of Sr₃Al₁₀SiO₂₀

In tristrontium decaaluminium silicon icosaoxide, Sr₃Al₁₀SiO₂₀, (Al,Si)O₄ tetrahedra and AlO₆ octahedra form a framework. Sr atoms occupy two large cavities of the framework. Sr2 and Al4 are on sites of 2/m symmetry, Al3 is on a twofold axis and Sr1 is on a mirror plane. The remaining Al and Si atoms are disordered over tetrahedral sites on general positions.

Key indicators

• Powder unknown study
• T = 293 K
• R factor = 0.060
• wR factor = 0.079
• Data-to-parameter ratio = 0.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level A:



DIFF_001  Alert A _diffrn_radiation_type is missing
          The radiation type should contain one of the following
          *  'Cu K\a'
          *  'Mo K\a'
          *  'Ag K\a'
          *  neutron
          *  synchrotron
          The following tests will not be performed.
          ABSMU_01,ABSTM_02,CRYSS_01,RADNW_01

DIFF_003  Alert A _diffrn_measurement_device_type is missing
          Diffractometer make and type. Replaces _diffrn_measurement_type.

RADNT_01  Alert A The radiation type should contain one of the following
          *  'Cu K\a'
          *  'Mo K\a'
          *  'Ag K\a'
          *  neutron
          *  synchrotron


 Alert Level C:



CELLV_02  Alert C The supplied cell volume s.u. differs from that
          calculated from the cell parameter s.u.'s by > 2
          Calculated cell volume su =      12.64
          Cell volume su given      =      16.00


 3 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

Al1 and Al2 are tetrahedrally coordinated with Si disordered over the two sites. These tetrahedra form six-membered rings in the bc plane which share corners with each other to form a chain parallel to the c axis. Individual chains are joined zigzag parallel to the b axis forming double layers by connecting the tetrahedra that point down in one chain with those that point up in the neighbouring chain. The Al3 and Al4 atoms are octahedrally coordinated. These octahedra share edges with each other and form a pillar parallel to the c axis. The pillars are separated from each other by the chains of six-membered rings and Sr2 atoms. The Sr atoms are inserted in cavities between the pillars and the chains and are arranged in columns parallel to the c axis. The Sr1 atoms are surrounded by one pillar and three chains and are coordinated by ten O atoms at an average distance of Sr1—O is 2.881 (6) Å. The Sr2 atoms are surrounded by two pillars and two chains and are coordinated by eight O atoms at an average distance of Sr2—O is 2.774 (7) Å. These distances are slightly longer than those of 2.67 (Sr1—O) and 2.70 Å (Sr2—O) found in Sr₂Al₆O₁₁, and 2.58 (Sr1—O) and 2.74 Å (Sr2—O) found in Sr₄Al₁₄O₂₁ (Smets et al., 1989). The Al3—O distances (average 1.93 Å) are longer than the Al4—O distances (average 1.88 Å). The same effect can be seen in case of Sr_1.33Pb_0.67Al₆O₁₁ (Plötz & Müller-Bushbaum, 1982) whose structure is the same as that of Sr₂Al₆O₁₁. In this compound, the Al–O distances in one of the octahedra are longer (average 1.93 Å) than those in the other (average 1.90 Å). In Sr₂Al₆O₁₁ and Sr₄Al₁₄O₂₁, the AlO₆ octahedra form walls parallel to the bc plane. In Sr₂Al₆O₁₁, (Al,Si)O₄ tetrahedra compose six-membered rings which are connected by sharing each corners and form walls parallel to the bc plane. On the other hand, in Sr₄Al₁₄O₂₁, there are no six-membered rings. In both compounds, Sr atoms are inserted in cavities between the tetrahedra and the walls formed by the octahedra.

S2. Experimental

A powder specimen of Sr₃Al₁₀SiO₂₀ was obtained by solid-state reaction. The sample of Sr₃Al₁₀SiO₂₀ was prepared by mixing stoichiometric quantities of SrCO₃, SiO₂ and Al₂O₃ (Rare Metallic Co., Ltd., the purity of >99.99%). A pressed pellet mixture was fired for 3 h at 1773 K, which is below the melting point, and quenched. The procedure was followed by regrinding, repelleting, and refiring twice.

S3. Refinement

Diffraction data were obtained on a Rigaku RINT 2500 V diffractometer system at 293 K. The Cu Kα radiation was selected by means of graphite monochromater. A system of diverging, anti-scattering and receiving slits of 0.5°, 0.5° and 0.15 mm, respectively, was used; two Soller slits were positioned both on the incident beam, before the divergent slit, and on the diffracted beam before the monochromator. In order to confirm the unit-cell parameters determined from the X-ray powder pattern, electron-diffraction patterns of Sr₃Al₁₀SiO₂₀ were recorded. The electron diffraction patterns were studied with a Jeol JEM-2000EX microscope (of Electron Microscope Laboratory of Tohoku University) operating at 200 kV. Fine powder specimens for electron microscopic observations were prepared by crushing the sintered products in an agate mortar. They were then mounted on collodion film meshes. Most of the electron-diffraction patterns could be indexed using the above lattice parameter.

Computing details

Data collection: RINT2500V Diffractometer Software (Rigaku, 1995); cell refinement: ITO (Visser, 1969); data reduction: RINT2500V Diffractometer Software; program(s) used to solve structure: EXPO (Altomare et al., 1994, 1995); program(s) used to refine structure: Rietan2000 (Izumi & Ikeda, 2000); molecular graphics: ATOMS (Dowty, 1999); software used to prepare material for publication: WORD97.

Figures

	Fig. 1. Comparison between the observed and calculated pattern and the difference curve.
	Fig. 2. The structure of Sr3Al10SiO20.

tristrontium decaaluminium silicon icosaoxide

Crystal data

Sr3Al10SiO20	V = 789.06 (16) Å^3
Mr = 880.75	Z = 2
Monoclinic, C2/m	? radiation, λ = 1.5418 Å
Hall symbol: -C_2	T = 293 K
a = 15.1416 (18) Å	white
b = 11.1843 (12) Å	flat sheet, 20 × 25 mm
c = 4.90256) Å	Specimen preparation: Prepared at 1773 K, cooled at quench K min^−1
β = 108.117 (5)°

Data collection

Graphite monochromator	2θmin = 5°, 2θmax = 140°, 2θstep = 0.02°
Data collection mode: reflection

Refinement

Refinement on Inet	6751 data points
Least-squares matrix: full with fixed elements per cycle	Profile function: pseudo-Voigt and Person 7 function
Rp = 0.060	41 parameters
Rwp = 0.079	Weighting scheme based on measured s.u.'s
Rexp = 0.051
χ^2 = 2.434	Preferred orientation correction: none

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.0855 (4)	0.2463 (5)	0.4289 (12)	0.0056 (8)*
Al1	0.1347 (3)	0.2119 (2)	0.1632 (8)	0.0037 (9)*	.875
Si1	0.1347 (3)	0.2119 (2)	0.1632 (8)	0.0037 (9)*	.125
O2	0.2398 (4)	0.1419 (5)	0.3237 (12)	0.0056 (8)*
Al2	0.3549 (3)	0.1381 (2)	0.3471 (8)	0.0089 (8)*	.875
Si2	0.3549 (3)	0.1381 (2)	0.3471 (8)	0.0089 (8)*	.125
O3	0.3604 (5)	0.1510 (4)	0.0032 (11)	0.0056 (8)*
O4	0.4279 (4)	0.3808 (5)	0.1046 (11)	0.0056 (8)*
O5	0.0658 (6)	0	0.3853 (17)	0.0056 (8)*
Sr1	0.2168 (1)	0	0.7386 (3)	0.0168 (6)*
O6	0.4013 (5)	0	0.4756 (16)	0.0056 (8)*
Al3	0	0.1280 (4)	0.5	0.0077 (11)*
Sr2	0	0.5	0	0.0127 (7)*
Al4	0	0	0	0.013 (2)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
?	?	?	?	?	?	?

Geometric parameters (Å, º)

Sr1—O5	2.401 (8)	Si1—O2	1.728 (6)
Sr1—O2	2.686 (6)	Si1—O1	1.734 (6)
Sr1—O2^i	2.686 (6)	Si1—O3^vii	1.749 (5)
Sr1—O3^ii	2.740 (6)	Al2—O2	1.711 (6)
Sr1—O3^iii	2.740 (6)	Al2—O3	1.720 (6)
Sr1—O4^iv	2.866 (6)	Al2—O6	1.732 (4)
Sr1—O4^v	2.866 (6)	Al2—O1^v	1.754 (6)
Sr1—O2^ii	3.201 (6)	Si2—O2	1.711 (6)
Sr1—O2^iii	3.201 (6)	Si2—O3	1.720 (6)
Sr1—O6	3.408 (8)	Si2—O6	1.732 (4)
Sr2—O6^vi	2.540 (8)	Si2—O1^v	1.754 (6)
Sr2—O6^v	2.540 (8)	Al3—O4^ix	1.908 (6)
Sr2—O3^vii	2.710 (6)	Al3—O4^v	1.908 (6)
Sr2—O3^vi	2.710 (6)	Al3—O5	1.925 (5)
Sr2—O3^viii	2.710 (6)	Al3—O5^x	1.925 (5)
Sr2—O3^ix	2.710 (6)	Al3—O1	1.957 (6)
Sr2—O6^vii	3.137 (8)	Al3—O1^xi	1.957 (6)
Sr2—O6^vi	3.137 (8)	Al4—O5	1.841 (8)
Al1—O4^vii	1.710 (6)	Al4—O5^xii	1.841 (8)
Al1—O2	1.728 (6)	Al4—O4^vii	1.892 (5)
Al1—O1	1.734 (6)	Al4—O4^ix	1.892 (5)
Al1—O3^vii	1.749 (5)	Al4—O4^xiii	1.892 (5)
Si1—O4^vii	1.710 (6)	Al4—O4^xiv	1.892 (5)
O4^vii—Al1—O2	106.7 (3)	O2—Si2—O1^v	109.8 (3)
O4^vii—Al1—O1	116.5 (4)	O4^ix—Al3—O4^v	174.1 (4)
O4^vii—Al1—O3^vii	105.5 (3)	O4^ix—Al3—O5	81.3 (3)
O4^vii—Si1—O2	106.7 (3)	O4^ix—Al3—O5^x	94.3 (3)
O4^vii—Si1—O1	116.5 (4)	O4^ix—Al3—O1	93.2 (3)
O4^vii—Si1—O3^vii	105.5 (3)	O4^ix—Al3—O1^xi	90.8 (3)
O2—Al2—O3	106.9 (3)	O5—Al4—O5^xii	180.0 (1)
O2—Al2—O6	109.6 (4)	O5—Al4—O4^vii	96.0 (2)
O2—Al2—O1^v	109.8 (3)	O5—Al4—O4^ix	84.0 (2)
O2—Si2—O3	106.9 (3)	O5—Al4—O4^xiii	96.0 (2)
O2—Si2—O6	109.6 (4)	O5—Al4—O4^xiv	84.01 (2)

Symmetry codes: (i) x, −y, z; (ii) x, y, z+1; (iii) x, −y, z+1; (iv) −x+1/2, y−1/2, −z+1; (v) −x+1/2, −y+1/2, −z+1; (vi) x−1/2, y+1/2, z; (vii) −x+1/2, −y+1/2, −z; (viii) −x+1/2, y+1/2, −z; (ix) x−1/2, −y+1/2, z; (x) −x, −y, −z+1; (xi) −x, y, −z+1; (xii) −x, −y, −z; (xiii) −x+1/2, y−1/2, −z; (xiv) x−1/2, y−1/2, z.