LiTb(PO3)4

inorganic papers

Acta Cryst.(2007). E63, i1–i2 doi:10.1107/S1600536806051737 Ben Zarkounaet al. _LiTb(PO

3)4

i1

Acta Crystallographica Section E Structure Reports

Online

ISSN 1600-5368

LiTb(PO

)

Emna Ben Zarkouna,aKarima

Horchani-Naifer,bMokhtar

Fe´ridb and Ahmed Drissa*

a_{Laboratoire de Mate´riaux et Cristallochimie,}

Faculte´ des Sciences, Universite´ Tunis-El Manar, 2092 El Manar, Tunis, Tunisia, andb_Laboratoire

des Mate´riaux, Institut National de Recherche Scientifique et Technique, BP 95 - 2050 Hammam-Lif, Tunisia

Correspondence e-mail: [email protected]

Key indicators

Single-crystal X-ray study

T= 293 K

Mean(P–O) = 0.003 A˚

Rfactor = 0.020

wRfactor = 0.054

Data-to-parameter ratio = 11.6

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

Received 27 November 2006 Accepted 29 November 2006

#2007 International Union of Crystallography

All rights reserved

The lithium terbium polyphosphate LiTb(PO3)4was prepared

by the flux method using a large excess of H3PO4. It was

structurally characterized by single-crystal X-ray diffraction

and found to be isotypic with LiYb(PO3)4. The basic structural

units are endless spiral chains, (PO3)n, along the b-axis

direction. The Li+and Tb3+cations alternate on twofold axes

and are four- and eight-coordinated, respectively. The results of an optical study of this material are also given and discussed.

Comment

The level of activity directed to the chemistry of lanthanide phosphates has steadily increased during the past three decades owing to their remarkable optical properties and high

luminescence efficiency (Bimberget al., 1975; Hashimotoet al.,

1991; Obaton et al., 2000). In particular, in our laboratories

much attention has been focused on the preparation and characterization of double phosphates combining monovalent and lanthanide cations in order to determine their structural,

optical and electrical features (Fe´rid, 2006; Ben Zarkouna et

al., 2006). In this context, we report here the chemical

preparation and structural and optical investigation of the

lithium terbium polyphosphate, LiTb(PO3)4.

The title compound is found to be isotypic with LiYb(PO3)4

(Ben Zarkouna & Driss, 2004). The basic structural units are

endless chains, (PO3)n, spiraling around the 21screw axes, in

theb-axis direction, with a period of four tetrahedra (Fig. 1).

These chains have a 21internal symmetry, so they are built up

by only two crystallographically independent PO4tetrahedra.

The bond lengths and angles within the phosphate chains are

Figure 1

The structural arrangement of LiTb(PO3)4 viewed along the [010]

typical of those observed in polyphosphates (Rzaigui, 1983) and, as expected, the longest P—O distances are found for the bridging P—O bonds, while the shortest are the ones involving

the terminal O atoms. As in KDyP4O12(Horchaniet al., 2002),

the alkali and lanthanide cations are located on twofold axes in thez=1

4and 3

4planes. However, in LiTb(PO3)4, the Li+and

Tb3+ cations alternate at almost equal spacings [3.51 (1) and

3.54 (1) A˚ ], compared with the quite different spacings of K+

and Dy3+ [3.743 (2) and 8.597 (2) A˚ ] in KDyP4O12. The

coordination environments of Li+ and Tb3+, in the present

structure, are formed by four and eight terminal O atoms,

respectively, in the shape of a distorted tetrahedron for Li+,

and an irregular dodecahedron for Tb3+; the mean Li—O and

Tb—O distances are 1.980 (7) and 2.412 (3) A˚ , respectively. It

can be noted that the TbO8 dodecahedra are isolated from

each other since they have no common O atom. The shortest

Tb Tb distance has a value of 5.598 (1) A˚ , somewhat greater

than that of the corresponding Yb Yb distance [5.545 (1) A˚ ]

in LiYb(PO3)4(Ben Zarkouna & Driss, 2004).

Under an UV excitation of 254 nm, LiTb(PO3)4 exhibits

green emission corresponding to the 5D4 ! 7Fj(j= 3,4,5,6)

electronic transitions of the Tb3+ ions; the dominant green

emission is around 545 nm and originates from the5_D

4!7F5

transition. No blue emission from the 5_D

3 level is observed.

This is typical of luminescent materials with a high

concen-tration of Tb3+, and it is due to the well known effect of

cross-relaxation, which results from a resonant energy transfer

between the 5D3!

5

D4and 7

F6 !

7

F0,1transitions of Tb

3+

ions (Berdowskiet al., 1985).

Experimental

A mixture of Li2CO3(2 g), Tb4O7(0.4 g) and H3PO4(85%, 16 ml) was slowly heated, in a vitreous carbon crucible, up to 620 K and held at this temperature for 10 d. After cooling to room temperature and removal of the excess phosphoric flux by boiling water, colourless crystals of LiTb(PO3)4 were gathered. Optical properties of LiTb(PO3)4were investigated at room temperature by means of a Jobin Yvon THR 1500 monochromator and a 254 nm Hg lamp as excitation source. The optical signal was detected by a Hamamatsu R928 photomultiplier.

Crystal data

LiTb(PO3)4

Mr= 481.74

Monoclinic,C2=c a= 16.358 (2) A˚ b= 7.050 (2) A˚ c= 9.629 (2) A˚

= 126.15 (1)

V= 896.7 (4) A˚3

Z= 4

Dx= 3.569 Mg m 3

MoKradiation

= 8.67 mm1

T= 293 (2) K Plate, colourless 0.280.160.08 mm

Data collection

Enraf–Nonius CAD-4 diffractometer

!/2scans

Absorption correction: scan (Northet al., 1968) Tmin= 0.236,Tmax= 0.646

974 independent reflections 951 reflections withI> 2(I) Rint= 0.016

max= 26.9

2 standard reflections frequency: 120 min

Refinement

Refinement onF2 R[F2_{> 2(F}2_{)] = 0.020}

wR(F2) = 0.054 S= 1.08 974 reflections 84 parameters

w= 1/[2

(Fo2) + (0.0344P)2

+ 5.8217P]

whereP= (Fo2+ 2Fc2)/3

(/)max< 0.001

max= 1.38 e A˚ 3

min=1.15 e A˚ 3

Extinction correction:SHELXL97 Extinction coefficient: 0.0025 (2)

Table 1

Selected geometric parameters (A˚ ,_).

Li—O2i

1.974 (8) Li—O6 1.987 (7) Tb—O3 2.312 (3) Tb—O1i

2.374 (3) Tb—O2ii

2.432 (3) Tb—O6 2.530 (3) P1—O1 1.488 (3)

P1—O6 1.502 (3) P1—O4 1.591 (3) P1—O5iii

1.596 (3) P2—O2 1.488 (3) P2—O3 1.490 (3) P2—O5 1.586 (3) P2—O4 1.606 (3)

O1—P1—O6 118.7 (2) O1—P1—O4 106.7 (2) O6—P1—O4 111.1 (1) O1—P1—O5iii 111.5 (2) O6—P1—O5iii

105.0 (1) O4—P1—O5iii

102.8 (1) O2—P2—O3 119.6 (2)

O2—P2—O5 107.9 (1) O3—P2—O5 111.9 (2) O2—P2—O4 104.8 (1) O3—P2—O4 109.8 (1) O5—P2—O4 101.0 (2) P1—O4—P2 131.5 (2) P2—O5—P1iv 134.6 (2)

Symmetry codes: (i)x;yþ1;z1

2; (ii)x;y;z 1

2; (iii) xþ 1 2;yþ

1 2;zþ

3 2; (iv)

xþ1 2;y

1 2;zþ

3 2.

The highest peak is located 0.90 A˚ from the Tb atom and the deepest hole is located 1.18 A˚ also from the Tb atom.

Data collection:CAD-4 EXPRESS(Duisenberg, 1992; Macı´cˇek & Yordanov, 1992); cell refinement:CAD-4 EXPRESS; data reduction:

XCAD4(Harms & Wocadlo, 1995); program(s) used to solve struc-ture:SHELXS97(Sheldrick, 1997); program(s) used to refine struc-ture:SHELXL97(Sheldrick, 1997); molecular graphics:DIAMOND

(Brandenburg, 1998); software used to prepare material for publi-cation:SHELXL97.

References

Ben Zarkouna, E. & Driss, A. (2004).Acta Cryst.E60, i102–i104. Ben Zarkouna, E., Driss, A. & Fe´rid, M. (2006).Acta Cryst.C62, i64–i66. Berdowski, P. A. M., Lammers, M. J. J. & Blasse, G. (1985).Chem. Phys. Lett.

113, 387–390.

Bimberg, D., Robbins, D. J., Wight, D. R. & Jeser, J. P. (1975).Appl. Phys. Lett. 27, 67–68.

Brandenburg, K. (1998).DIAMOND. Version 2.0. Crystal Impact GbR, Bonn, Germany.

Duisenberg, A. J. M. (1992).J. Appl. Cryst.25, 92–96.

Fe´rid, M. (2006). Etude des proprie´te´s cristallochimiques et physiques de phosphates condense´s de terres rares. Paris: Publibook.

Harms, K. & Wocadlo, S. (1995).XCAD4. University of Marburg, Germany. Hashimoto, N., Takada, Y., Sato, K. & Ibuki, S. (1991).J. Lumin.48–49, 893–

897.

Horchani, K., Fe´rid, M., Gaˆcon, J. C., Lecocq, S., Trabelsi-Ayadi, M. & Gregora, I. (2002).Mater. Res. Bull.37, 1259–1267.

Macı´cˇek, J. & Yordanov, A. (1992).J. Appl. Cryst.25, 73–80.

North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968).Acta Cryst.A24, 351– 359.

Obaton, A. F., Parent, C., Le Flem, G., Thony, P., Brenier, A. & Boulon, G. (2000).J. Alloys Compd.300–301, 123–130.

Rzaigui, M. (1983). PhD thesis, University of Tunis, Tunisia.

supporting information

sup-1 Acta Cryst. (2007). E63, i1–i2

supporting information

Acta Cryst. (2007). E63, i1–i2 [https://doi.org/10.1107/S1600536806051737]

LiTb(PO

)

Emna Ben Zarkouna, Karima Horchani-Naifer, Mokhtar F

é

rid and Ahmed Driss

lithium terbium polyphosphate

Crystal data

LiTb(PO3)4

Mr = 481.74

Monoclinic, C2/c

Hall symbol: -C 2yc

a = 16.358 (2) Å

b = 7.050 (2) Å

c = 9.629 (2) Å

β = 126.15 (1)°

V = 896.7 (4) Å3

Z = 4

F(000) = 896

Dx = 3.569 Mg m−3

Mo Kα radiation, λ = 0.71069 Å Cell parameters from 25 reflections

θ = 10.7–14.7°

µ = 8.67 mm−1

T = 293 K Plate, colourless 0.28 × 0.16 × 0.08 mm

Data collection

Enraf–Nonius CAD-4 diffractometer

Radiation source: fine-focus sealed tube Graphite monochromator

ω/2θ scans

Absorption correction: ψ scan (North et al., 1968)

Tmin = 0.236, Tmax = 0.646

1324 measured reflections

974 independent reflections 951 reflections with I > 2σ(I)

Rint = 0.016

θmax = 26.9°, θmin = 3.1°

h = −20→17

k = −1→8

l = −1→12

2 standard reflections every 120 min intensity decay: 1%

Refinement

Refinement on F2

Least-squares matrix: full

R[F2 _{> 2σ(F}2_{)] = 0.020}

wR(F2_{) = 0.054}

S = 1.08 974 reflections 84 parameters 0 restraints

Primary atom site location: heavy-atom method

Secondary atom site location: difference Fourier map

w = 1/[σ2_(F

o2) + (0.0344P)2 + 5.8217P]

where P = (Fo2 + 2Fc2)/3

(Δ/σ)max < 0.001

Δρmax = 1.38 e Å−3

Δρmin = −1.15 e Å−3

Extinction correction: SHELXL97, Fc*_{=kFc[1+0.001xFc}2_λ3_/sin(2θ)]-1/4

Extinction coefficient: 0.0025 (2)

Special details

Refinement. Refinement of F2 _{against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F}2_,

conventional R-factors R are based on F, with F set to zero for negative F2_{. The threshold expression of F}2 _{> σ(F}2_{) 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₎

x y z Uiso*/Ueq

Li 0.0000 0.705 (1) 0.2500 0.018 (2)

Tb 0.0000 0.20252 (3) 0.2500 0.0065 (1)

P1 0.13795 (7) 0.5530 (1) 0.6151 (1) 0.0064 (2)

P2 0.14715 (7) 0.1520 (1) 0.6974 (1) 0.0068 (2)

O1 0.1137 (2) 0.7167 (4) 0.6825 (4) 0.0121 (6)

O2 0.0719 (2) 0.0871 (4) 0.7268 (4) 0.0106 (5)

O3 0.1286 (2) 0.1149 (4) 0.5286 (3) 0.0116 (5)

O4 0.1578 (2) 0.3762 (4) 0.7340 (3) 0.0108 (5)

O5 0.2555 (2) 0.0801 (4) 0.8536 (3) 0.0104 (5)

O6 0.0653 (2) 0.5027 (4) 0.4280 (3) 0.0097 (5)

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

Li 0.024 (6) 0.016 (6) 0.016 (5) 0.000 0.013 (5) 0.000 Tb 0.0053 (2) 0.0071 (2) 0.0066 (2) 0.000 0.0031 (1) 0.000 P1 0.0045 (4) 0.0069 (5) 0.0069 (4) −0.0004 (3) 0.0029 (4) −0.0002 (3) P2 0.0047 (4) 0.0079 (4) 0.0075 (4) 0.0000 (3) 0.0035 (4) 0.0011 (3) O1 0.011 (1) 0.012 (1) 0.016 (1) −0.000 (1) 0.009 (1) −0.003 (1) O2 0.006 (1) 0.011 (1) 0.017 (1) 0.000 (1) 0.008 (1) 0.002 (1) O3 0.012 (1) 0.012 (1) 0.009 (1) 0.001 (1) 0.005 (1) 0.000 (1) O4 0.016 (1) 0.007 (1) 0.010 (1) −0.000 (1) 0.008 (1) 0.000 (1) O5 0.006 (1) 0.016 (1) 0.010 (1) 0.001 (1) 0.005 (1) 0.002 (1) O6 0.005 (1) 0.012 (1) 0.008 (1) −0.002 (1) 0.002 (1) 0.000 (1)

Geometric parameters (Å, º)

Li—O2i _{1.974 (8) Tb—O2}vi _{2.432 (3)}

Li—O2ii _{1.974 (8) Tb—O6 2.530 (3)}

Li—O6iii _{1.987 (7) Tb—O6}iii _{2.530 (3)}

Li—O6 1.987 (7) P1—O1 1.488 (3)

Li—Tbiv _{3.509 (10) P1—O6 1.502 (3)}

Li—Tb 3.541 (10) P1—O4 1.591 (3)

Tb—O3iii _{2.312 (3) P1—O5}vii _{1.596 (3)}

Tb—O3 2.312 (3) P2—O2 1.488 (3)

Tb—O1i _{2.374 (3) P2—O3 1.490 (3)}

Tb—O1ii _{2.374 (3) P2—O5 1.586 (3)}

Tb—O2v _{2.432 (3) P2—O4 1.606 (3)}

supporting information

sup-3 Acta Cryst. (2007). E63, i1–i2

O2i_—Li—O6iii _{119.23 (11) O4—P1—O5}vii _{102.8 (1)}

O2ii_—Li—O6iii _{125.26 (11) O2—P2—O3 119.6 (2)}

O2i_{—Li—O6 125.26 (11) O2—P2—O5 107.9 (1)}

O2ii_{—Li—O6 119.23 (11) O3—P2—O5 111.9 (2)}

O6iii_{—Li—O6 88.4 (4) O2—P2—O4 104.8 (1)}

O1—P1—O6 118.7 (2) O3—P2—O4 109.8 (1)

O1—P1—O4 106.7 (2) O5—P2—O4 101.0 (2)

O6—P1—O4 111.1 (1) P1—O4—P2 131.5 (2)

O1—P1—O5vii _{111.5 (2) P2—O5—P1}viii _{134.6 (2)}