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The title compound, tricadmium trizinc tetraborate, Cd3Zn3(BO3)4, is a new non-linear optical (NLO) crystal and its structure has been determined by single-crystal X-ray diffraction. This compound is composed of planar [BO3]3- groups sharing O atoms with CdO4 or ZnO4 tetrahedra. The BO3 triangles are located on threefold axes and are arranged with nearly the same orientation. The Cd and Zn atoms are disordered on the same site in the proportion 1:1. A strong second harmonic generation of Nd:YAG laser radiation ([lambda] = 1064 nm) has been observed for a crystal of the title compound.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103020390/sk1661sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103020390/sk1661Isup2.hkl
Contains datablock I

Comment top

To date, many promising borate materials have been discovered and studied for second? harmonic generation of laser radiation to produce new laser sources in the visible and UV spectroscopic ranges, such as β-Ba2B2O4 (BBO; Chen et al., 1985), LiB3O5 (LBO; Chen et al., 1989), CsLiB6O10 (CLBO; Mori et al., 1995), KBe2BO3F2 (KBBF; Mei et al., 1995), Sr2Be2B2O7 (SBBO; Chen et al., 1995) and K2Al2B2O7 (KAB; Hu et al., 1998). Few borate NLO materials incorporating transition metal elements have been researched, except BaZn2(BO3)2 (Smith & Keszler, 1992), Ba2Zn(BO3)2 (Smith & Keszler, 1994) and ReCa4O(BO3)3 (Re is Y or Gd; Iwai et al., 1997). Whitaker & Channell (1993) investigated the ternary system CdO-ZnO-B2O3 at 1123 K and a new phase, Cd3Zn3B4O12, was postulated for the first time. Based on their study, we have grown single crystals of Cd3Zn3(BO3)4 (abbreviated to CZBO). To the best of our knowledge, CZBO has not previously been grown as a single-crystal.

The crystal structure of trigonal CZBO is characterized by a three-dimensional framework built from corner-sharing BO3 triangles with CdO4 or ZnO4 tetrahedra (Fig. 1). In this configuration, each O atom belongs to two tetrahedra and a triangle. All [BO3]3− trigonal groups are almost perfectly planar and perpendicular to the c axis. The BO3 triangles in the different layers are orientated in nearly the same direction and are only slightly rotated around the threefold axis. The B1—O and B2—O bond lengths are nearly equal [1.377 (3) and 1.374 (4) Å, respectively]. The O—B—O bond angles are very close to 120°.

The Cd2+ and Zn2+ cations in CZBO share the same site in the unit cell and are distributed in a disorderly fashion. The occupancy of the metal position was assigned to be 0.5 C d+0.5Zn, according to the result of an ICP-AES analysis. The Cd(Zn)O4 moiety is distorted from an ideal tetrahedron and the four O atoms connect to different B atoms (Fig. 2). The Cd/Zn—O distances lie between 2.014 (3) and 2.131 (4) Å, and the O—Cd/Zn—O angles are in the range 92.04 (14)–128.39 (11)°. CdB4O7 (Ihara & Krogh-Moe, 1966) and Zn3B2O6 (Baur & Tillmanns, 1970) also contain (CdO4)6− and (ZnO4)6− groups, respectively, with similar bond lengths and angles. The average Cd/Zn—O bond length in CZBO is shorter than the average of the Cd—O bonds in Cd3B2O6 (Laureiro et al., 1991), because the ionic radius of Zn2+ is smaller than that of Cd2+, and also because Cd is coordinated by six O atoms in the structure of Cd3B2O6.

Chen et al. (1990) classified known NLO borate crystals by their coordinated anionic groups and succeeded in predicting second-order NLO susceptibilities. According to their classification, the NLO-active clusters in CZBO should be the anionic groups, [BO3]3−. It is favourable for the superposition of microscopic second-order NLO susceptibilities if the planar [BO3]3− groups are arranged with the same orientation in the structure of CZBO. In addition, the presence of distorted Cd(Zn)O4 tetrahedra sharing vertices with BO3 triangles may not only enhance the NLO effect, but also make CZBO easier to grow, because of strong binding between the layered structural units. The structural features indicated above show that CZBO is a potential NLO crystal. In fact, a strong second harmonic generation (SHG) of Nd:YAG laser radiation (λ 1064 nm) was observed on the as-grown single crystals.

Experimental top

Crystals of the title compound were grown by spontaneous nucleation in a platinum crucible using a vertical cylindrical electric furnace. Starting materials were prepared from a mixture of 43.9 wt% CdO, 27.9 wt% ZnO and 28.2 wt% H3BO3. Crystal growth was carried out at 1170 K under an air ambient. A clear colourless single-crystal of CZBO, with a size of 3 × 1.5 × 1 mm, was obtained.

Refinement top

The systematic absences of hkil with −h+k+l = 3n, hh2(-h)l with l = 3n, h(-h)0 l with 2 h+l = 3n and l = 2n showed that the space group should be R3c or R3c. However, the nonlinear optical properties of the crystal suggested that the space group must be the noncentrosymmetrical space group, R3c. The metal ions, Cd2+ and Zn2+, share the same site. According to the results of ICP-AES and occupancy refinement, the occupancy of the metal site was assigned to be 0.5 C d+0.5Zn in the final refinement.

Computing details top

Data collection: XSCANS (Bruker, 1997); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL (Bruker, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. A view of the molecular packing in CZBO along the [001] direction. Small shaded circles represent B atoms and small open circles represent O atoms, while large hatched circles depict Cd or Zn atoms.
[Figure 2] Fig. 2. A view of the molecule of CZBO with 50% probability displacement ellipsoids, showing the atomic numbering scheme. Cd and Zn share the same site. [Symmetry codes: (a) 1 − y, 1 + x-y, z; (b) 2 − y, 2 + x-y, z; (c) y-x, 1 − x, z; (d) y-x, 2 − x, z; (e) 4/3 − y, 5/3 − x, 1/6 + z; (f) 1/3 + x, 5/3 + x-y, 1/6 + z; (g) 5/3 − y, 4/3 − x, z − 1/6; (h) x − 1/3, 4/3 + x-y, z − 1/6.]
tricadmium trizinc tetraborate top
Crystal data top
Cd3Zn3(BO3)4Dx = 5.145 Mg m3
Mr = 768.64Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3cCell parameters from 21 reflections
Hall symbol: R 3 -2"cθ = 4.8–14.7°
a = 8.364 (6) ŵ = 13.52 mm1
c = 12.286 (10) ÅT = 293 K
V = 744.3 (10) Å3Block, colourless
Z = 30.12 × 0.10 × 0.10 mm
F(000) = 1050
Data collection top
Bruker P4
diffractometer
526 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.094
Graphite monochromatorθmax = 32.5°, θmin = 4.4°
ω scansh = 1212
Absorption correction: ψ
(North et al., 1968)
k = 1212
Tmin = 0.195, Tmax = 0.260l = 1818
3235 measured reflections3 standard reflections every 100 reflections
607 independent reflections intensity decay: none
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0013P)2 + 35.8548P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.052(Δ/σ)max = 0.031
wR(F2) = 0.121Δρmax = 1.59 e Å3
S = 1.07Δρmin = 1.38 e Å3
607 reflectionsExtinction correction: SHELXL97 Ref, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
35 parametersExtinction coefficient: 0.01004 (19)
1 restraintAbsolute structure: Flack (1983), with x Friedel pairs
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.11 (16)
Crystal data top
Cd3Zn3(BO3)4Z = 3
Mr = 768.64Mo Kα radiation
Trigonal, R3cµ = 13.52 mm1
a = 8.364 (6) ÅT = 293 K
c = 12.286 (10) Å0.12 × 0.10 × 0.10 mm
V = 744.3 (10) Å3
Data collection top
Bruker P4
diffractometer
526 reflections with I > 2σ(I)
Absorption correction: ψ
(North et al., 1968)
Rint = 0.094
Tmin = 0.195, Tmax = 0.2603 standard reflections every 100 reflections
3235 measured reflections intensity decay: none
607 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.052 w = 1/[σ2(Fo2) + (0.0013P)2 + 35.8548P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.121Δρmax = 1.59 e Å3
S = 1.07Δρmin = 1.38 e Å3
607 reflectionsAbsolute structure: Flack (1983), with x Friedel pairs
35 parametersAbsolute structure parameter: 0.11 (16)
1 restraint
Special details top

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) top
xyzUiso*/UeqOcc. (<1)
Cd10.35586 (4)1.01497 (6)0.85915 (17)0.04746 (9)0.50
Zn10.35586 (4)1.01497 (6)0.85915 (17)0.04746 (9)0.50
B10.66671.33330.7318 (6)0.0310 (15)
B20.33330.66670.8113 (6)0.0343 (18)
O10.5513 (4)1.1448 (4)0.7314 (3)0.0433 (8)
O20.2261 (4)0.7485 (4)0.8122 (3)0.0463 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cd10.02540 (10)0.03586 (12)0.07608 (18)0.01155 (8)0.00405 (16)0.02080 (12)
Zn10.02540 (10)0.03586 (12)0.07608 (18)0.01155 (8)0.00405 (16)0.02080 (12)
B10.0251 (16)0.0251 (16)0.043 (3)0.0125 (8)0.0000.000
B20.0286 (18)0.0286 (18)0.046 (4)0.0143 (9)0.0000.000
O10.0341 (10)0.0255 (9)0.0664 (17)0.0120 (8)0.0029 (12)0.0054 (11)
O20.0425 (10)0.0415 (10)0.0655 (17)0.0290 (7)0.0042 (12)0.0063 (12)
Geometric parameters (Å, º) top
Cd1—O22.014 (3)B1—O1iv1.377 (3)
Cd1—O1i2.016 (4)B1—O11.377 (3)
Cd1—O2ii2.095 (4)B1—O1v1.377 (3)
Cd1—O12.131 (4)B2—O21.374 (4)
Cd1—Cd1i3.3451 (18)B2—O2vi1.374 (4)
Cd1—Cd1iii3.3451 (18)B2—O2vii1.374 (4)
Zn1—O22.014 (3)O1—Zn1iii2.016 (4)
Zn1—O1i2.016 (4)O1—Cd1iii2.016 (4)
Zn1—O2ii2.095 (4)O2—Zn1viii2.096 (4)
Zn1—O12.131 (4)O2—Cd1viii2.096 (4)
O2—Cd1—O1i115.23 (12)O1iv—B1—O1v119.998 (8)
O2—Cd1—O2ii128.39 (11)O1—B1—O1v119.999 (8)
O1i—Cd1—O2ii99.95 (14)O2—B2—O2vi119.994 (12)
O2—Cd1—O1101.80 (15)O2—B2—O2vii119.994 (12)
O1i—Cd1—O1118.55 (17)O2vi—B2—O2vii119.994 (11)
O2ii—Cd1—O192.04 (14)B1—O1—Zn1iii120.0 (2)
O2—Cd1—Cd1i142.72 (10)B1—O1—Cd1iii120.0 (2)
O1i—Cd1—Cd1i37.41 (9)B1—O1—Zn1120.0 (3)
O2ii—Cd1—Cd1i62.69 (9)Zn1iii—O1—Zn1107.49 (14)
O1—Cd1—Cd1i113.94 (10)Cd1iii—O1—Zn1107.49 (14)
O2—Cd1—Cd1iii74.67 (10)B1—O1—Cd1120.0 (3)
O1i—Cd1—Cd1iii152.12 (11)Zn1iii—O1—Cd1107.49 (14)
O2ii—Cd1—Cd1iii91.70 (10)Cd1iii—O1—Cd1107.49 (14)
O1—Cd1—Cd1iii35.09 (10)B2—O2—Cd1115.39 (19)
Cd1i—Cd1—Cd1iii142.32 (3)B2—O2—Zn1115.39 (19)
O2—Zn1—O1i115.23 (12)B2—O2—Zn1viii118.9 (3)
O2—Zn1—O2ii128.39 (11)Cd1—O2—Zn1viii115.94 (18)
O1i—Zn1—O2ii99.95 (14)Zn1—O2—Zn1viii115.94 (18)
O2—Zn1—O1101.80 (15)B2—O2—Cd1viii118.9 (3)
O1i—Zn1—O1118.55 (17)Cd1—O2—Cd1viii115.94 (18)
O2ii—Zn1—O192.04 (14)Zn1—O2—Cd1viii115.94 (18)
O1iv—B1—O1119.999 (6)
Symmetry codes: (i) y+4/3, x+5/3, z+1/6; (ii) x+1/3, xy+5/3, z+1/6; (iii) y+5/3, x+4/3, z1/6; (iv) y+2, xy+2, z; (v) x+y, x+2, z; (vi) x+y, x+1, z; (vii) y+1, xy+1, z; (viii) x1/3, xy+4/3, z1/6.

Experimental details

Crystal data
Chemical formulaCd3Zn3(BO3)4
Mr768.64
Crystal system, space groupTrigonal, R3c
Temperature (K)293
a, c (Å)8.364 (6), 12.286 (10)
V3)744.3 (10)
Z3
Radiation typeMo Kα
µ (mm1)13.52
Crystal size (mm)0.12 × 0.10 × 0.10
Data collection
DiffractometerBruker P4
diffractometer
Absorption correctionψ
(North et al., 1968)
Tmin, Tmax0.195, 0.260
No. of measured, independent and
observed [I > 2σ(I)] reflections
3235, 607, 526
Rint0.094
(sin θ/λ)max1)0.757
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.052, 0.121, 1.07
No. of reflections607
No. of parameters35
No. of restraints1
w = 1/[σ2(Fo2) + (0.0013P)2 + 35.8548P]
where P = (Fo2 + 2Fc2)/3
Δρmax, Δρmin (e Å3)1.59, 1.38
Absolute structureFlack (1983), with x Friedel pairs
Absolute structure parameter0.11 (16)

Computer programs: XSCANS (Bruker, 1997), XSCANS, SHELXTL (Bruker, 1997), SHELXTL.

Selected geometric parameters (Å, º) top
Cd1—O22.014 (3)Zn1—O1i2.016 (4)
Cd1—O1i2.016 (4)Zn1—O2ii2.095 (4)
Cd1—O2ii2.095 (4)Zn1—O12.131 (4)
Cd1—O12.131 (4)B1—O11.377 (3)
Zn1—O22.014 (3)B2—O21.374 (4)
O2—Cd1—O1i115.23 (12)O2—B2—O2v119.994 (12)
O2—Cd1—O2ii128.39 (11)O2—B2—O2vi119.994 (12)
O1i—Cd1—O2ii99.95 (14)O2v—B2—O2vi119.994 (11)
O2—Cd1—O1101.80 (15)B1—O1—Cd1vii120.0 (2)
O1i—Cd1—O1118.55 (17)B1—O1—Cd1120.0 (3)
O2ii—Cd1—O192.04 (14)Cd1vii—O1—Cd1107.49 (14)
O1iii—B1—O1119.999 (6)B2—O2—Cd1115.39 (19)
O1iii—B1—O1iv119.998 (8)B2—O2—Cd1viii118.9 (3)
O1—B1—O1iv119.999 (8)Cd1—O2—Cd1viii115.94 (18)
Symmetry codes: (i) y+4/3, x+5/3, z+1/6; (ii) x+1/3, xy+5/3, z+1/6; (iii) y+2, xy+2, z; (iv) x+y, x+2, z; (v) x+y, x+1, z; (vi) y+1, xy+1, z; (vii) y+5/3, x+4/3, z1/6; (viii) x1/3, xy+4/3, z1/6.
 

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