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Acta Crystallogr Sect E Struct Rep Online. 2010 February 1; 66(Pt 2): i4.
Published online 2010 January 9. doi:  10.1107/S1600536810000358
PMCID: PMC2979930

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


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 An external file that holds a picture, illustration, etc.
Object name is e-66-000i4-efi1.jpg 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 [triangle]). For borophosphate structures, see: Ewald et al. (2007 [triangle]); Mi et al. (1999 [triangle]); Schmidt et al. (2004 [triangle]); Schulze (1934 [triangle]); Dachille & Glasser (1959 [triangle]); Mackenzie et al. (1959 [triangle]). For the catalytic properties of BPO4, see: Moffat (1978 [triangle]); Moffat & Schmidtmeyer (1986 [triangle]); Mooney (1956 [triangle]); Morey et al. (1983 [triangle]); Tada et al. (1987 [triangle]); Tartarelli et al. (1970 [triangle]). For crystallographic background, see: Finger et al. (1994 [triangle])); Thompson et al. (1987 [triangle]).


Crystal data

  • (Ga0.71B0.29)PO4
  • M r = 147.61
  • Tetragonal, An external file that holds a picture, illustration, etc.
Object name is e-66-000i4-efi2.jpg
  • 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
  • min = 15.03°, 2θmax = 100.02°, 2θstep = 0.01°


  • R p = 0.076
  • R wp = 0.129
  • R exp = 0.072
  • R(F 2) = 0.07586
  • χ2 = 3.204
  • 8500 data points
  • 35 parameters
  • 2 restraints

Cell refinement: GSAS (Larson & Von Dreele, 2004 [triangle]); data reduction: GSAS; program(s) used to refine structure: GSAS (Larson & Von Dreele, 2004 [triangle]); molecular graphics: DIAMOND (Brandenburg, 2005 [triangle]); software used to prepare material for publication: GSAS.

Table 1
Selected bond lengths (Å)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810000358/br2131sup1.cif

Rietveld powder data: contains datablocks I. DOI: 10.1107/S1600536810000358/br2131Isup2.rtv

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


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

supplementary crystallographic information


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, while for the P nodes, giving the net symbol ( 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.


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.


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.


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.
Fig. 2.
The crystal structure of (Ga0.71B0.29)PO4 viewed along the a-axis. (Ga,B)O4 tetrahedra: blue, PO4 tetrahedra: orange.
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.

Crystal data

(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

Rigaku-D/max automatic powder diffractometerData collection mode: reflection
graphiteScan method: step
Specimen mounting: packed powder pelletmin = 15.03°, 2θmax = 100.02°, 2θstep = 0.01°


Least-squares matrix: full8500 data points
Rp = 0.076Profile function: Thompson et al. (1987); Finger et al. (1994); Stephens et al. (1999)
Rwp = 0.12935 parameters
Rexp = 0.0722 restraints
R(F2) = 0.07586(Δ/σ)max = 0.001
χ2 = 3.204Background 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

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

xyzUiso*/UeqOcc. (<1)
Ga10. (12)*0.7002 (4)
Ga20. (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. (12)*0.2998 (4)
B20. (11)*0.2821 (3)

Geometric parameters (Å, °)

(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, z−1; (ii) x, y+1, z−1; (iii) y, −x+1, −z+1; (iv) y+1, −x+1, −z+1; (v) −x+1, −y+1, z−1; (vi) −y+1, x, −z+1; (vii) x−1, y, z; (viii) y, −x, −z+1; (ix) −x+1, −y, z; (x) −y, x−1, −z+1; (xi) x, y−1, z; (xii) −x+1, −y+1, z; (xiii) x+1, y, z; (xiv) x, y, z+1; (xv) x, y+1, z.


Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BR2131).


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