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Acta Crystallogr Sect E Struct Rep Online. 2010 October 1; 66(Pt 10): i72.
Published online 2010 September 18. doi:  10.1107/S1600536810036445
PMCID: PMC2983292

A ramsayite-type oxide, Ca2Sn2Al2O9

Abstract

The title compound, dicalcium nonaoxidodistannate(IV)dialuminate, is the second example which crystallizes in the isotypic structure of a pyroxene silicate, Na2Ti2Si2O9 (ramsayite). 1[Sn2O8] chains and pyroxene-type 1[Al2O6] chains are formed along the b axis by sharing O atoms. The Ca atoms are situated in the resulting channels and exhibit a coordination number of 7.

Related literature

For the structure of ramsayite, Na2Ti2Si2O9, see: Sundberg et al. (1987 [triangle]). For the synthesis of Ca8Sn7Al10O37, see: Barbanyagre & Kotlyarov (2001 [triangle]). For the structure of a related stannate silicate, Ca2SnSi2O9, see: Blasse et al. (1995 [triangle]). For bond-valence parameters, see: Brese & O’Keeffe (1991 [triangle]). For the CaO–Al2O3 system, see: Jerebtsov & Mikhailov (2001 [triangle]). For the Inorganic Crystal Structure Database, see: ICSD (2009 [triangle]).

Experimental

Crystal data

  • Ca2Sn2Al2O9
  • M r = 515.50
  • Orthorhombic, An external file that holds a picture, illustration, etc.
Object name is e-66-00i72-efi1.jpg
  • a = 8.9866 (6) Å
  • b = 5.4894 (11) Å
  • c = 14.9030 (18) Å
  • V = 735.18 (18) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 8.46 mm−1
  • T = 293 K
  • 0.17 × 0.15 × 0.07 mm

Data collection

  • Rigaku R-AXIS RAPID diffractometer
  • Absorption correction: numerical (NUMABS; Higashi, 1999 [triangle]) T min = 0.427, T max = 0.717
  • 6534 measured reflections
  • 845 independent reflections
  • 788 reflections with I > 2σ(I)
  • R int = 0.051

Refinement

  • R[F 2 > 2σ(F 2)] = 0.018
  • wR(F 2) = 0.043
  • S = 1.08
  • 845 reflections
  • 69 parameters
  • Δρmax = 0.72 e Å−3
  • Δρmin = −0.72 e Å−3

Data collection: PROCESS-AUTO (Rigaku, 1998 [triangle]); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku, 2005 [triangle]); program(s) used to solve structure: SIR2004 (Burla et al., 2005 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: VESTA (Momma & Izumi, 2008 [triangle]); software used to prepare material for publication: SHELXL97.

Table 1
Selected bond lengths (Å)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810036445/br2147sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810036445/br2147Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

This work was supported in part by a Grant-in-Aid for Scientific Research (B) (No. 21350113, 2009) from the Ministry of Education, Culture, Sports and Technology (MEXT), Japan, and performed under the auspices of the Inter-university Cooperative Research Program of the Institute for Materials Research, Tohoku University.

supplementary crystallographic information

Comment

Barbanyagre and Kotlyarov (2001) reported a quaternary oxide Ca8Al10Sn7O37 with a powder X-ray diffraction (PXRD) pattern, but they did not clarify the crystal structure. We have prepared single crystals of Ca2Sn2Al2O9 by slow cooling of a Ca—Al—Sn—O melt. The PXRD pattern of Ca8Al10Sn7O37 was similar to that calculated with the crystal structure parameters of Ca2Sn2Al2O9 analyzed by the present study.

Ca2Sn2Al2O9 is isostructural with ramsayite (lorenzenite) Na2Ti2Si2O9 (a = 8.7128 (10), b = 5.2327 (5), c = 14.487 (2) Å) (Sundberg, et al., 1987). Other compounds crystallizing in the isotypic structure were not found in the Inorganic Crystal Structure Database (ICSD, 2009).

The selected bond distances in Ca2Sn2Al2O9 are summarized in Table 1. The coordination environments of Ca, Sn and Al are drawn with displacement ellipsoids in Fig. 1. The Sn site is in a distorted oxygen octhahedron with the Sn—O distances varying from 2.002 (2) to 2.207 (2) Å, (average 2.08 (8) Å). The bond valence sum (BVS) calculated for Sn atoms with the bond valence parameter of R (Sn—O) = 1.905 Å (Brese & O'Keeffe, 1991) was 3.815, a little smaller than the IV valence of Sn. These Sn—O bond lengths and the BVS are consistent with those reported for Ca3SnSi2O9 (2.007–2.134 Å, avg. 2.08 (4) Å, BVS 3.803) (Blasse et al., 1995).

Each SnO6 octahedron shares O1—O3 edges with both adjacent sides of SnO6 octahedra and a one-dimensional chain 1[Sn2O8] is formed along the b axis. Al atoms are tetrahedrally coordinated by O atoms and the AlO4 tetrahedra form pyroxene-type 1[Ali2O6] chains along the b axis by sharing O2. The Al—O bond lengths are from 1.735 to 1.777 (3) Å (avg. 1.755 (19) Å) and the BVS of 3.02 is consistent with trivalent of Al(III). The chains of 1[Ali2O6] and 1[Sn2O8] are bridged by sharing O4, and the 1[Sn2O8] chains are linked each other by sharing O5 on a two-fold axis, forming rectangular channels along the b axis (Fig. 2). Ca sites are situated in the channels and surrounded by 7 oxygen atoms with the distances from 2.303 (2) to 2.624 (2) Å. The BVS of Ca atoms is 2.01 and well agrees with the valence number of Ca(II).

A permittivity of 48 and a tanδ of 0.02 were measured at room temperature with an impedance analyzer (Solartron 1260 and 1296) for the polycrystalline sample which was mainly composed of Ca2Sn2Al2O9 with a small amount of CaSnO3 which crystallized at the initial stage of solid state reaction.

Experimental

The starting materials used were CaCO3 (Rare Metallic, 99.99% purity), SnO2 (Rare Metallic, 99.99% purity) and Al2O3 (Rare Metallic, 99.99% purity). The powders were weighed, mixed in an agate mortar with a pestle, and pressed into pellets, which were placed on a platinum plate and heated in an electric furnace in air. Single crystals of Ca2Sn2Al2O9 were prepared from a starting mixture with an atomic ratio Ca: Sn: Al ═ 5:1:4. The pellet of the mixture was heated to 1823 K at a heating rate of 200 K/h, and then cooled to 1773 K at a cooling rate of 5 K/h. The single crystals were probably grown in a flux with a composition close to a Ca3Al2O6—CaAl2O4 mixture which has the eutectic point of 1644 K (Jerebtsov & Mikhailov, 2001). The samples were then cooled in the furnace by shutting off the electric power. The obtained sample was crushed into fragments and colorless transparent single crystals of about 0.06–0.14 mm were picked up under an optical microscope. A polycrystalline sample was prepared by heating the pellets of the starting mixtures with stoichiometric metal ratios Ca:Sn:Al ═ 1:1:1 at around 1600 K for 24 h.

Refinement

The highest peak in the difference electron density map is 0.94 Å from Sn1 while the deepest hole is 1.08 Å from the same atom.

Figures

Fig. 1.
O-atom coordination around Ca, Al, and Sn atoms in the structure of Ca2Sn2Al2O9. Displacement ellipsoids are drawn at 99% probability level. [Symmetry codes as in Table 1.]
Fig. 2.
Crystal structure of Ca2Sn2Al2O9 illustrated with distorted Sn-centered oxygen octahedra and Al-centered oxygen tetrahedra.

Crystal data

Ca2Sn2Al2O9F(000) = 952
Mr = 515.50Dx = 4.657 Mg m3
Orthorhombic, PbcnMo Kα radiation, λ = 0.71075 Å
Hall symbol: -P 2n 2abCell parameters from 5414 reflections
a = 8.9866 (6) Åθ = 3.6–27.8°
b = 5.4894 (11) ŵ = 8.46 mm1
c = 14.9030 (18) ÅT = 293 K
V = 735.18 (18) Å3Platelet, colourless
Z = 40.17 × 0.15 × 0.07 mm

Data collection

Rigaku R-AXIS RAPID diffractometer845 independent reflections
Radiation source: fine-focus sealed tube788 reflections with I > 2σ(I)
graphiteRint = 0.051
Detector resolution: 10.00 pixels mm-1θmax = 27.5°, θmin = 3.6°
ω scansh = −11→11
Absorption correction: numerical (NUMABS; Higashi, 1999)k = −7→7
Tmin = 0.427, Tmax = 0.717l = −19→19
6534 measured reflections

Refinement

Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.018Secondary atom site location: difference Fourier map
wR(F2) = 0.043w = 1/[σ2(Fo2) + (0.002P)2 + 2.2176P] where P = (Fo2 + 2Fc2)/3
S = 1.08(Δ/σ)max = 0.001
845 reflectionsΔρmax = 0.72 e Å3
69 parametersΔρmin = −0.72 e Å3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/Ueq
Ca10.06714 (7)0.36160 (11)0.14603 (5)0.00676 (14)
Al10.34369 (10)0.31037 (18)0.02817 (7)0.0055 (2)
Sn10.34459 (2)0.36611 (4)0.333981 (15)0.00525 (9)
O10.1618 (2)0.1912 (4)0.40897 (16)0.0070 (5)
O20.2277 (2)0.0795 (4)0.07144 (15)0.0071 (4)
O30.3314 (2)0.0365 (4)0.27250 (16)0.0079 (5)
O40.5156 (2)0.2310 (4)0.07402 (16)0.0078 (4)
O50.00000.0250 (6)0.25000.0077 (6)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Ca10.0069 (3)0.0071 (3)0.0062 (3)−0.0007 (2)0.0006 (2)−0.0003 (2)
Al10.0057 (5)0.0058 (5)0.0050 (5)−0.0001 (3)−0.0004 (3)0.0001 (4)
Sn10.00529 (13)0.00501 (14)0.00544 (14)0.00004 (7)−0.00022 (7)−0.00022 (8)
O10.0080 (11)0.0067 (11)0.0064 (12)−0.0008 (8)−0.0004 (8)−0.0002 (9)
O20.0089 (11)0.0054 (10)0.0070 (11)−0.0007 (8)−0.0005 (9)−0.0003 (9)
O30.0077 (11)0.0064 (11)0.0096 (13)−0.0008 (8)0.0026 (9)−0.0019 (9)
O40.0059 (10)0.0088 (11)0.0087 (11)−0.0003 (8)−0.0024 (9)−0.0011 (9)
O50.0086 (15)0.0078 (15)0.0066 (16)0.000−0.0014 (13)0.000

Geometric parameters (Å, °)

Ca1—O3i2.303 (2)Sn1—O1i2.106 (2)
Ca1—O22.391 (2)Sn1—O12.207 (2)
Ca1—O1ii2.404 (2)O1—Al1vii1.777 (3)
Ca1—O4i2.412 (2)O1—Sn1viii2.106 (2)
Ca1—O2i2.463 (2)O1—Ca1ii2.404 (2)
Ca1—O52.486 (2)O2—Al1viii1.735 (2)
Ca1—O3iii2.624 (2)O2—Ca1viii2.463 (2)
Al1—O2i1.735 (2)O3—Sn1viii2.053 (2)
Al1—O41.745 (2)O3—Ca1viii2.303 (2)
Al1—O21.763 (2)O3—Ca1ix2.624 (2)
Al1—O1iv1.777 (3)O4—Sn1v2.002 (2)
Sn1—O4v2.002 (2)O4—Ca1viii2.412 (2)
Sn1—O32.032 (2)O5—Sn1x2.0682 (13)
Sn1—O3i2.053 (2)O5—Sn1viii2.0682 (13)
Sn1—O5vi2.0682 (13)O5—Ca1ii2.486 (2)
O3i—Ca1—O2114.30 (8)O3i—Sn1—O1i80.21 (9)
O3i—Ca1—O1ii141.26 (8)O5vi—Sn1—O1i88.98 (9)
O2—Ca1—O1ii96.08 (8)O4v—Sn1—O187.66 (9)
O3i—Ca1—O4i97.80 (8)O3—Sn1—O178.32 (9)
O2—Ca1—O4i121.59 (8)O3i—Sn1—O181.41 (9)
O1ii—Ca1—O4i84.93 (8)O5vi—Sn1—O1173.05 (6)
O3i—Ca1—O2i82.57 (8)O1i—Sn1—O194.57 (9)
O2—Ca1—O2i69.69 (4)Al1vii—O1—Sn1viii121.70 (13)
O1ii—Ca1—O2i132.50 (8)Al1vii—O1—Sn1121.93 (11)
O4i—Ca1—O2i67.76 (7)Sn1viii—O1—Sn196.90 (9)
O3i—Ca1—O584.02 (7)Al1vii—O1—Ca1ii108.61 (10)
O2—Ca1—O587.41 (7)Sn1viii—O1—Ca1ii97.21 (9)
O1ii—Ca1—O573.48 (6)Sn1—O1—Ca1ii107.17 (10)
O4i—Ca1—O5145.85 (7)Al1viii—O2—Al1134.02 (15)
O2i—Ca1—O5145.50 (6)Al1viii—O2—Ca1120.07 (11)
O3i—Ca1—O3iii77.78 (9)Al1—O2—Ca193.51 (9)
O2—Ca1—O3iii159.97 (8)Al1viii—O2—Ca1viii91.78 (9)
O1ii—Ca1—O3iii67.00 (8)Al1—O2—Ca1viii94.11 (10)
O4i—Ca1—O3iii69.47 (7)Ca1—O2—Ca1viii123.82 (10)
O2i—Ca1—O3iii129.46 (7)Sn1—O3—Sn1viii104.43 (10)
O5—Ca1—O3iii77.73 (6)Sn1—O3—Ca1viii135.82 (11)
O2i—Al1—O4113.24 (12)Sn1viii—O3—Ca1viii118.71 (10)
O2i—Al1—O2104.92 (9)Sn1—O3—Ca1ix94.02 (9)
O4—Al1—O2101.59 (11)Sn1viii—O3—Ca1ix104.41 (10)
O2i—Al1—O1iv111.43 (12)Ca1viii—O3—Ca1ix84.64 (7)
O4—Al1—O1iv114.50 (11)Al1—O4—Sn1v137.01 (13)
O2—Al1—O1iv110.23 (11)Al1—O4—Ca1viii96.38 (10)
O4v—Sn1—O390.89 (9)Sn1v—O4—Ca1viii101.55 (9)
O4v—Sn1—O3i163.28 (9)Sn1x—O5—Sn1viii130.13 (15)
O3—Sn1—O3i99.18 (9)Sn1x—O5—Ca1ii121.78 (5)
O4v—Sn1—O5vi98.44 (7)Sn1viii—O5—Ca1ii95.75 (4)
O3—Sn1—O5vi98.16 (9)Sn1x—O5—Ca195.75 (4)
O3i—Sn1—O5vi93.33 (8)Sn1viii—O5—Ca1121.78 (5)
O4v—Sn1—O1i88.14 (9)Ca1ii—O5—Ca183.96 (10)
O3—Sn1—O1i172.86 (9)

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

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2147).

References

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  • Higashi, T. (1999). NUMABS Rigaku Corporation, Tokyo, Japan.
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  • Jerebtsov, D. A. & Mikhailov, G. G. (2001). Ceram. Int.27, 25–28.
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