inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

(Ga0.71B0.29)PO4 with a high-cristobalite-type structure refined from powder data

aDepartment of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005, People's Republic of China, and bChinese Academy of Sciences, Shanghai Institute of Ceramics, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, 1295 Dingxi Road, Shanghai 200050, People's Republic of China
*Correspondence e-mail: yaxihuang@xmu.edu.cn

(Received 16 December 2009; accepted 5 January 2010; online 9 January 2010)

Gallium boron phosphate, (Ga0.71B0.29)PO4, was synthesized by a high-temperature solid-state reaction method. The crystal structure is isostructural with the tetra­gonal high-cristobalite structure with space group P[\overline{4}] which is built from alternating Ga(B)O4 and PO4 tetra­hedra inter­connected by sharing the common O-atom vertices, resulting in a three-dimensional structure with two-dimensional six-membered-ring tunnels running along the a and b axes.

Related literature

For information on cristobalite structures, see: Achary et al. (2003[Achary, S. N., Jayakumar, O. D., Tyagi, A. K. & Kulshreshtha, S. K. (2003). J. Solid State Chem. 176, 37-46.]). For borophosphate structures, see: Ewald et al. (2007[Ewald, B., Huang, Y.-X. & Kniep, R. (2007). Z. Anorg. Allg. Chem. 633, 1517-1540.]); Mi et al. (1999[Mi, J.-X., Mao, S.-Y., Chen, Z.-H., Huang, Z.-L. & Zhao, J.-T. (1999). Chin. Chem. Lett. 10, 707-708.]); Schmidt et al. (2004[Schmidt, M., Ewald, B., Prots, Yu., Cardoso-Gil, R., Armbrüster, M., Loa, I., Zhang, L., Huang, Y.-X., Schwarz, U. & Kniep, R. (2004). Z. Anorg. Allg. Chem. 630, 655-662.]); Schulze (1934[Schulze, G. E. R. (1934). Z. Phys. Chem. 24, 215-240.]); Dachille & Glasser (1959[Dachille, F. & Glasser, L. S. D. (1959). Acta Cryst. 12, 820-821.]); Mackenzie et al. (1959[Mackenzie, J. D., Roth, W. L. & Wentorf, R. H. (1959). Acta Cryst. 12, 79.]). For the catalytic properties of BPO4, see: Moffat (1978[Moffat, J. B. (1978). Catal. Rev. Sci. Eng. 18, 199-258.]); Moffat & Schmidtmeyer (1986[Moffat, J. B. & Schmidtmeyer, A. (1986). Appl. Catal. 28, 161-168.]); Mooney (1956[Mooney, R. C. L. (1956). Acta Cryst. 9, 728-734.]); Morey et al. (1983[Morey, J., Marinas, J. M. & Sinisterra, J. V. (1983). React. Kinet. Catal. Lett. 22, 175-180.]); Tada et al. (1987[Tada, A., Suzuka, H. & Imizu, Y. (1987). Chem. Lett. 2, 423-424.]); Tartarelli et al. (1970[Tartarelli, R., Giorgini, M., Lucchesi, A., Stoppato, G. & Moreli, F. (1970). J. Catal. 17, 41-45.]). For crystallographic background, see: Finger et al. (1994[Finger, L. W., Cox, D. E. & Jephcoat, A. P. (1994). J. Appl. Cryst. 27, 892-900.])); Thompson et al. (1987[Thompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79-83.]).

Experimental

Crystal data
  • (Ga0.71B0.29)PO4

  • Mr = 147.61

  • Tetragonal, [P \overline 4]

  • a = 4.7343 (1) Å

  • c = 7.0896 (4) Å

  • V = 158.90 (1) Å3

  • Z = 2

  • Cu Kα1, Cu Kα2 radiation

  • λ = 1.5405, 1.5443 Å

  • T = 293 K

  • flat sheet, 10 × 10 mm

Data collection
  • Rigaku-D/max automatic powder diffractometer

  • Specimen mounting: packed powder pellet

  • Data collection mode: reflection

  • Scan method: step

  • 2θmin = 15.03°, 2θmax = 100.02°, 2θstep = 0.01°

Refinement
  • Rp = 0.076

  • Rwp = 0.129

  • Rexp = 0.072

  • R(F2) = 0.07586

  • χ2 = 3.204

  • 8500 data points

  • 35 parameters

  • 2 restraints

Table 1
Selected bond lengths (Å)

(Ga/B)1—O2i 1.7079 (5)
(Ga/B)2—O1ii 1.6979 (5)
P1—O1 1.499 (3)
Symmetry codes: (i) x, y, z-1; (ii) x-1, y, z.

Cell refinement: GSAS (Larson & Von Dreele, 2004[Larson, A. C. & Von Dreele, R. B. (2004). General Structure Analysis System (GSAS). Report LAUR, 86-748. Los Alamos National Laboratory, New Mexico, USA.]); data reduction: GSAS; program(s) used to refine structure: GSAS (Larson & Von Dreele, 2004[Larson, A. C. & Von Dreele, R. B. (2004). General Structure Analysis System (GSAS). Report LAUR, 86-748. Los Alamos National Laboratory, New Mexico, USA.]); molecular graphics: DIAMOND (Brandenburg, 2005[Brandenburg, K. (2005). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: GSAS.

Supporting information


Comment top

The high-cristobalite boron phosphate has long been used as an effective catalyst for various organic reactions such as hydration, dehydration, oligomerization (Moffat, 1978; Moffat & Schmidtmeyer, 1986; Morey et al., 1983; Tada et al., 1987; Tartarelli et al., 1970). The catalytic activities depend on the ratio of P/B and surface area. In the case of excess B content, BPO4 catalysts consist predominately of Lewis acid sites, and show catalytic efficiencies for the dehydration. In contrast, in a region consisting of excess phosphorus P content, BPO4 catalysts have more Brønsted acid sites and exhibit catalytic activities for hydration. Applying trivalent cations to partially substitute boron may vary the ratio of P/B and modify the catalytic property. The possibility of modifying the catalytic properties by varieties of P/B ratio and searching for new phases in the borophosphate system intrigue us to investigate systems containing larger trivalent metal cations. In our previous investigations, a series of compounds with boron partially substituted by transition metals, such as Mn, Fe, Co, Ni, and Cu, has been characterized with low cristobalite type structure (Mi et al., 1999). When we applied a smaller trivalent element Ga to modify the BPO4, the occupancy of Ga is more than 50%, while less than 50% for transition metal compounds (M = Mn, Fe, Co, Ni, and Cu). In consequence, the structure of (Ga0.71B0.29)PO4 are high-cristobalite structure instead of low-cristobalite type structure.

The crystal structure of (Ga0.71B0.29)PO4 is isostructural with the tetragonal high-cristobalite structure (Schulze, 1934; Schmidt et al., 2004) with space group P4 which is built from alternating (Ga, B)O4 and PO4 tetrahedra interconnected by sharing the common O-vertices, resulting in a three dimensional network with two dimensional 6-membered ring tunnels running along the a- and b-axis, respectively. Every TO4 (T = Ga(B), P) tetrahedron connects to four neighboring TO4 tetrahedra. There are three types of positions for T-atoms. (Ga, B)1 and (Ga, B)2 sit at 1c and 1b, while P at 2g. The long (Schläfli) notation for (Ga, B) nodes is 62.62.62.62.62.62, while 62.62.62.62.62.62 for the P nodes, giving the net symbol (62.62.62.62.62.62)3 which can be represented by the short symbol (66)3.

The (Ga, B)1–O and (Ga, B)2–O bond distances are 1.7079 (5) Å and 1.6979 (5) Å in the (Ga, B)O4 tetrahedra which are significantly larger than the B–O bond value of 1.463 Å in BPO4 (Schmidt et al., 2004), but smaller than the bond values of 1.829 Å for Ga–O bond in GaPO4 (Achary et al., 2003), indicating that boron and gallium occupy the same position. After refining both the atomic occupation number and displacement parameters, it results in the ratio of Ga:B = 0.71:0.29. In turn, the Ga:P is 1.42:2, which is quite good agreement with that (Ga:P = 3:4) in the reactants for obtaining the pure phase. The introduction of gallium in the compound led to the deformation of all the tetrahedra and quite anisotropic expansion of the structure which results in lowering symmetry from space group I4 of BPO4 to P4 for the new compound.

Related literature top

For information on cristobalite structures, see: Achary et al. (2003). For borophosphate structures, see: Ewald et al. (2007); Mi et al. (1999); Schmidt et al. (2004); Schulze (1934). For the catalytic properties of BPO4, see: Moffat (1978); Moffat & Schmidtmeyer (1986); Mooney (1956); Morey et al. (1983); Tada et al. (1987); Tartarelli et al. (1970). For related literature, see: Dachille & Glasser (1959); Mackenzie et al. (1959).For crystallographic background, see: Finger et al. (1994); Thompson et al. (1987).

Experimental top

The title compound has been synthesized via high temperature solid state reaction method and the structure refined from X-ray powder diffraction data. A mixture of H3BO3, NH4H2PO4, and Ga2O3 with molar ratio of B:Ga:P = 12:3:4 was well ground and reacted first at 973 K for 4 h, then cooled down to room temperature and reground again, pressed into pellets and reacted at 1373 K for 8 h, at last shut down the furnace and cooled down to room temperature. The extra B2O3 in the products were washed out by hot water.

Refinement top

The cell parameters were obtained by least-square fits of the powder diffractometer data using silicon (a = 5.4308 Å) as an internal standard. Although the powder pattern and cell parameters are quite different from BPO4, the starting atomic positional parameters can still be derived from the prototype BPO4 (Schmidt et al., 2004). During the initial refinement, the unreasonable negative thermal parameters for the B position are indicative of partial substitutions by Ga. The boron position then were assumed to be occupied by two kinds of atoms and the occupacies were allowed to vary during the subsequent refinements. Because it is difficult to refine both the occupation numbers and atomic displacement parameters at the same time, a two-step process was applied to refine the occupancy numbers and atomic displacement parameters. At the begining, all the atomic displacement parameters were set to one value to refine the occupancy number, then fixed the occupany number to refine the displacement parameters. Both processes were performed alternately several times till reasonable values for both atomic occupancies and displacement parameters were obtained. Due to the individual refinement, the standard deviations given by the program are much too small to be a realistic estimate of the uncertainty.

Structure description top

The high-cristobalite boron phosphate has long been used as an effective catalyst for various organic reactions such as hydration, dehydration, oligomerization (Moffat, 1978; Moffat & Schmidtmeyer, 1986; Morey et al., 1983; Tada et al., 1987; Tartarelli et al., 1970). The catalytic activities depend on the ratio of P/B and surface area. In the case of excess B content, BPO4 catalysts consist predominately of Lewis acid sites, and show catalytic efficiencies for the dehydration. In contrast, in a region consisting of excess phosphorus P content, BPO4 catalysts have more Brønsted acid sites and exhibit catalytic activities for hydration. Applying trivalent cations to partially substitute boron may vary the ratio of P/B and modify the catalytic property. The possibility of modifying the catalytic properties by varieties of P/B ratio and searching for new phases in the borophosphate system intrigue us to investigate systems containing larger trivalent metal cations. In our previous investigations, a series of compounds with boron partially substituted by transition metals, such as Mn, Fe, Co, Ni, and Cu, has been characterized with low cristobalite type structure (Mi et al., 1999). When we applied a smaller trivalent element Ga to modify the BPO4, the occupancy of Ga is more than 50%, while less than 50% for transition metal compounds (M = Mn, Fe, Co, Ni, and Cu). In consequence, the structure of (Ga0.71B0.29)PO4 are high-cristobalite structure instead of low-cristobalite type structure.

The crystal structure of (Ga0.71B0.29)PO4 is isostructural with the tetragonal high-cristobalite structure (Schulze, 1934; Schmidt et al., 2004) with space group P4 which is built from alternating (Ga, B)O4 and PO4 tetrahedra interconnected by sharing the common O-vertices, resulting in a three dimensional network with two dimensional 6-membered ring tunnels running along the a- and b-axis, respectively. Every TO4 (T = Ga(B), P) tetrahedron connects to four neighboring TO4 tetrahedra. There are three types of positions for T-atoms. (Ga, B)1 and (Ga, B)2 sit at 1c and 1b, while P at 2g. The long (Schläfli) notation for (Ga, B) nodes is 62.62.62.62.62.62, while 62.62.62.62.62.62 for the P nodes, giving the net symbol (62.62.62.62.62.62)3 which can be represented by the short symbol (66)3.

The (Ga, B)1–O and (Ga, B)2–O bond distances are 1.7079 (5) Å and 1.6979 (5) Å in the (Ga, B)O4 tetrahedra which are significantly larger than the B–O bond value of 1.463 Å in BPO4 (Schmidt et al., 2004), but smaller than the bond values of 1.829 Å for Ga–O bond in GaPO4 (Achary et al., 2003), indicating that boron and gallium occupy the same position. After refining both the atomic occupation number and displacement parameters, it results in the ratio of Ga:B = 0.71:0.29. In turn, the Ga:P is 1.42:2, which is quite good agreement with that (Ga:P = 3:4) in the reactants for obtaining the pure phase. The introduction of gallium in the compound led to the deformation of all the tetrahedra and quite anisotropic expansion of the structure which results in lowering symmetry from space group I4 of BPO4 to P4 for the new compound.

For information on cristobalite structures, see: Achary et al. (2003). For borophosphate structures, see: Ewald et al. (2007); Mi et al. (1999); Schmidt et al. (2004); Schulze (1934). For the catalytic properties of BPO4, see: Moffat (1978); Moffat & Schmidtmeyer (1986); Mooney (1956); Morey et al. (1983); Tada et al. (1987); Tartarelli et al. (1970). For related literature, see: Dachille & Glasser (1959); Mackenzie et al. (1959).For crystallographic background, see: Finger et al. (1994); Thompson et al. (1987).

Computing details top

Data collection: PLEASE SUPPLY; cell refinement: PLEASE SUPPLY; data reduction: GSAS (Larson & Von Dreele, 2004); program(s) used to solve structure: PLEASE SUPPLY; program(s) used to refine structure: GSAS (Larson & Von Dreele, 2004); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: PLEASE SUPPLY.

Figures top
[Figure 1] Fig. 1. Experimental (points) and calculated (lines) X-ray diffraction patterns of (Ga0.71B0.29)PO4. The difference profile is given at the bottom. The Bragg positions are indicated by the vertical marker below the observed pattern.
[Figure 2] Fig. 2. The crystal structure of (Ga0.71B0.29)PO4 viewed along the a-axis. (Ga,B)O4 tetrahedra: blue, PO4 tetrahedra: orange.
[Figure 3] Fig. 3. Topological figure for the network of (Ga0.71B0.29)PO4, oxygen atoms were omitted for clarity. Ga(B) atoms: blue spheres, P atoms: purple spheres.
gallium boron phosphate top
Crystal data top
(Ga0.71B0.29)PO4Z = 2
Mr = 147.61F(000) = 140.4
Tetragonal, P4Dx = 3.084 Mg m3
Hall symbol: P -4Cu Kα1, Cu Kα2 radiation, λ = 1.540500, 1.544300 Å
a = 4.7343 (1) ÅT = 293 K
c = 7.0896 (4) Åwhite
V = 158.90 (1) Å3flat sheet, 10 × 10 mm
Data collection top
Rigaku-D/max automatic powder
diffractometer
Data collection mode: reflection
Graphite monochromatorScan method: step
Specimen mounting: packed powder pellet2θmin = 15.026°, 2θmax = 100.016°, 2θstep = 0.01°
Refinement top
Least-squares matrix: fullProfile function: Thompson et al. (1987); Finger et al. (1994); Stephens et al. (1999)
Rp = 0.07635 parameters
Rwp = 0.1292 restraints
Rexp = 0.072(Δ/σ)max = 0.001
R(F2) = 0.07586Background function: The background function is a cosine Fourier series with a leading constant term. Ib= B1+ΣBjcos[P*(j-1)] (j=2-9), here P = 2θ, Bj (j = 1-9) values are given below: 1: 935.903 2: -1634.98 3: 1422.47 4: -1094.93 5: 681.394 6: -358.046 7: 116.953 8: -17.2104 9: -22.9558
8500 data points
Crystal data top
(Ga0.71B0.29)PO4V = 158.90 (1) Å3
Mr = 147.61Z = 2
Tetragonal, P4Cu Kα1, Cu Kα2 radiation, λ = 1.540500, 1.544300 Å
a = 4.7343 (1) ÅT = 293 K
c = 7.0896 (4) Åflat sheet, 10 × 10 mm
Data collection top
Rigaku-D/max automatic powder
diffractometer
Scan method: step
Specimen mounting: packed powder pellet2θmin = 15.026°, 2θmax = 100.016°, 2θstep = 0.01°
Data collection mode: reflection
Refinement top
Rp = 0.0768500 data points
Rwp = 0.12935 parameters
Rexp = 0.0722 restraints
R(F2) = 0.07586
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Ga10.50.50.00.0347 (12)*0.7002 (4)
Ga20.00.00.50.0406 (11)*0.7179 (3)
P10.50.00.7456 (5)0.0447 (12)*
O10.7299 (3)0.1326 (3)0.6304 (5)0.0493 (15)*
O20.6286 (3)0.7718 (4)0.8669 (5)0.0511 (16)*
B10.50.50.00.0347 (12)*0.2998 (4)
B20.00.00.50.0406 (11)*0.2821 (3)
Geometric parameters (Å, º) top
(Ga/B)1—P1i2.9759 (8)(Ga/B)2—O1ix1.6979 (5)
(Ga/B)1—P1ii2.9759 (8)(Ga/B)2—O1x1.6979 (5)
(Ga/B)1—P1iii2.9759 (8)P1—O11.499 (3)
(Ga/B)1—P1iv2.9759 (8)P1—O1ix1.499 (3)
(Ga/B)1—O2i1.7079 (5)P1—O2xi1.509 (3)
(Ga/B)1—O2iii1.7079 (5)P1—O2xii1.509 (3)
(Ga/B)1—O2v1.7079 (5)B1—O2i1.7079 (5)
(Ga/B)1—O2vi1.7079 (5)B1—O2iii1.7079 (5)
(Ga/B)2—P1vii2.9386 (8)B1—O2v1.7079 (5)
(Ga/B)2—P12.9386 (8)B1—O2vi1.7079 (5)
(Ga/B)2—P1viii2.9386 (8)B2—O1vii1.6979 (5)
(Ga/B)2—P1iii2.9386 (8)B2—O1iii1.6979 (5)
(Ga/B)2—O1vii1.6979 (5)B2—O1ix1.6979 (5)
(Ga/B)2—O1iii1.6979 (5)B2—O1x1.6979 (5)
O2i—(Ga/B)1—O2iii107.765 (2)O2xi—P1—O2xii110.502 (4)
O2i—(Ga/B)1—O2v112.941 (3)(Ga/B)2xiii—O1—P1133.541 (1)
O2i—(Ga/B)1—O2vi107.765 (2)P1—O1—B2xiii133.541 (1)
O2iii—(Ga/B)1—O2v107.765 (2)(Ga/B)1xiv—O2—P1xv135.267 (1)
O2iii—(Ga/B)1—O2vi112.941 (3)P1xv—O2—B1xiv135.267 (1)
O2v—(Ga/B)1—O2vi107.765 (2)O2i—B1—O2iii107.765 (2)
O1vii—(Ga/B)2—O1iii107.239 (2)O2i—B1—O2v112.941 (3)
O1vii—(Ga/B)2—O1ix114.035 (3)O2i—B1—O2vi107.765 (2)
O1vii—(Ga/B)2—O1x107.239 (2)O2iii—B1—O2v107.765 (2)
O1iii—(Ga/B)2—O1ix107.239 (2)O2iii—B1—O2vi112.941 (3)
O1iii—(Ga/B)2—O1x114.035 (3)O2v—B1—O2vi107.765 (2)
O1ix—(Ga/B)2—O1x107.239 (2)O1vii—B2—O1iii107.239 (2)
O1—P1—O1ix113.942 (3)O1vii—B2—O1ix114.035 (3)
O1—P1—O2xi108.506 (2)O1vii—B2—O1x107.239 (2)
O1—P1—O2xii107.696 (2)O1iii—B2—O1ix107.239 (2)
O1ix—P1—O2xi107.696 (2)O1iii—B2—O1x114.035 (3)
O1ix—P1—O2xii108.506 (2)O1ix—B2—O1x107.239 (2)
Symmetry codes: (i) x, y, z1; (ii) x, y+1, z1; (iii) y, x+1, z+1; (iv) y+1, x+1, z+1; (v) x+1, y+1, z1; (vi) y+1, x, z+1; (vii) x1, y, z; (viii) y, x, z+1; (ix) x+1, y, z; (x) y, x1, z+1; (xi) x, y1, z; (xii) x+1, y+1, z; (xiii) x+1, y, z; (xiv) x, y, z+1; (xv) x, y+1, z.

Experimental details

Crystal data
Chemical formula(Ga0.71B0.29)PO4
Mr147.61
Crystal system, space groupTetragonal, P4
Temperature (K)293
a, c (Å)4.7343 (1), 7.0896 (4)
V3)158.90 (1)
Z2
Radiation typeCu Kα1, Cu Kα2, λ = 1.540500, 1.544300 Å
Specimen shape, size (mm)Flat sheet, 10 × 10
Data collection
DiffractometerRigaku-D/max automatic powder
diffractometer
Specimen mountingPacked powder pellet
Data collection modeReflection
Scan methodStep
2θ values (°)2θmin = 15.026 2θmax = 100.016 2θstep = 0.01
Refinement
R factors and goodness of fitRp = 0.076, Rwp = 0.129, Rexp = 0.072, R(F2) = 0.07586, χ2 = 3.204
No. of parameters35
No. of restraints2

Computer programs: PLEASE SUPPLY, GSAS (Larson & Von Dreele, 2004), DIAMOND (Brandenburg, 2005).

Selected bond lengths (Å) top
(Ga/B)1—O2i1.7079 (5)P1—O11.499 (3)
(Ga/B)2—O1ii1.6979 (5)
Symmetry codes: (i) x, y, z1; (ii) x1, y, z.
 

Acknowledgements

This project was supported by the National Natural Science Foundation of China (No. 40972035) and State `973' project (No. 2007CB936704).

References

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