Synthesis and characterization of a new layered lithium zinc phosphate hydrate

Article abstract of DOI:10.1006/jssc.2001.9337

A new layered lithium zinc phosphate hydrate, Li₂Zn(HPO₄)₂· 0.66H₂O, isostructural with Na₂Zn(HPO₄)₂·4H₂O was prepared by the direct ambient pressure and temperature reaction between zinc 2,4-pentanedionate, phosphoric acid, and lithium hydroxide. The as-prepared sample is monoclinic (a = 8.896(8) A, b = 13.092(5) A, c = 10.882(9) A, and β = 115.760(6)°). The prepared solid undergoes three thermal transformations when it is heated from 110 to 600°C. The first two transformations are due to the release of intercalated water molecules and the third one is due to the HPO₄^2--P₂O₇^4- transition.

Full text of DOI:10.1006/jssc.2001.9337

Journal of Solid State Chemistry 162, 29}33 (2001)
doi:10.1006/jssc.2001.9337, available online at http://www.idealibrary.com on
Synthesis and Characterization of a New Layered Lithium
Zinc Phosphate Hydrate
A. Bensalemꢀ
Chemistry Department, Long Island University, 1 University Plaza, Brooklyn, New York 11201
Received March 5, 2001; in revised form July 19, 2001; accepted August 2, 2001
Na Zn(HPO ) ) 4H O using a simple ambient conditions
ꢁ
ꢂ ꢁ
ꢁ
A new layered lithium zinc phosphate hydrate, Li
.66H O, isostructural with Na Zn(HPO '4H
pared by the direct ambient pressure and temperature reaction
between zinc 2,4-pentanedionate, phosphoric acid, and lithium
2
Zn(HPO
O was pre-
4
)
2
'
synthetic method. The prepared solid was characterized by
X-ray powder di!raction and IR spectroscopy. The thermal
transformations were investigated by thermogravimetric
measurements (TG), di!erential scanning calorimetry
0
2
2
)
4 2
2
hydroxide. The as-prepared sample is monoclinic (a ؍ 8.896(8) A
s
,
(
DSC), and X-ray powder di!raction.
b ؍ 13.092(5) A, c ؍ 10.882(9) A, and b ؍ 115.760(6)3). The pre-
s
s
pared solid undergoes three thermal transformations when it is
heated from 110 to 6003C. The 5rst two transformations are due
to the release of intercalated water molecules and the third one is
EXPERIMENTAL
2
4
؊
4؊
7
The title compound was prepared at room temperature
by mixing in distilled water zinc 2,4-pentanedionate
Zn(C H O ) )H O (Johnson Matthey Electronics) with
phosphoric acid (99.999%, 85 wt%, Aldrich Chemical Co.)
and lithium hydroxide (Aldrich Chemical Co.) in a com-
position of Zn(C H O ) )H O:2H PO :2LiOH. The reac-
due to the HPO
+P
2
O
transition. ( 2001 Academic Press
Key Words: layered phosphate; zincophosphate; ambient con-
ditions; intercalated water molecules.
ꢃ ꢄ ꢁ ꢁ
ꢁ
INTRODUCTION
ꢃ ꢄ ꢁ ꢁ
ꢁ
ꢅ
ꢂ
tion mixture led to the formation of a gelatinous white
Layered acid phosphates are of continuing academic and precipitate. The precipitate was recovered by "ltration
industrial interest because of their extensive use as hetero- and dried at 1103C for 2 h. The dry white powder was
geneous catalysts (1}3). Some of them can undergo ion analyzed by
exchange and reversible hydration in the same way as
* X-ray powder di!raction (XRD) using a SCINTAG
zeolites. Recently, we developed a new room-temperature automated PAD-X di!ractometer utilizing monochromatic
synthetic route for the preparation of layered acid phos- CuKa radiation. The di!raction patterns were taken in
phates of magnesium. The interlayer species were water the range of 53(2h(703. The 2h step size was 0.043 and
(4, 5), ethanol, and ethylene glycol (6). The water interca- the count time was 1 s. Quartz was used as an internal
lated magnesium phosphate can undergo reversible dehy- standard. Cell parameters were obtained from a least-
dration}rehydration provided it is not heated beyond squares re"nement of the XRD data with the aid of a
2
003C. There is a growing interest in the preparation of new computer program, which corrected for the systematic
non-aluminosilicate framework materials with structures experimental errors.
that include very large pores. Indeed, some of the zinc
* Thermogravimetric analysis (TGA) and di!erential
phosphate structures exhibit channels with diameters ex- scanning calorimetry (DSC) using a TG7/DSC Perkin}
ceeding 14 A
>
(7}9).
Elmer thermal analyzer connected to a thermal analysis
Recently, Harrison and co-workers (10) prepared a system. Samples were heated at a rate of 103/min in a nitro-
new layered two-dimensional zincophosphate material, gen atmosphere, with a gas #ow rate of 25 ml/min. All the
Na Zn (HPO ) )4H O, containing a network of layers of sample weights were in the 10- to 20-mg range.
ꢁ
ꢂ ꢁ
ꢁ
bifurcated tetrahedral 12-rings connected by sodium cations
* Fourier transform infrared (FTIR) spectroscopy using
and H-bonds. Here, we report the preparation of a a Nicolet Impact 400 spectrometer in the wavelength range
new layered lithium zinc phosphate isostructural with of 1400}400 cm\ꢀ. The FTIR spectra were taken on KBr
pellets. The spectra were composites of 64 individual scans
and were all taken under a dry nitrogen atmosphere at room
ꢀ
Fax: 718-488-1465. E-mail: azzedine.bensalem@liu.edu.
temperature.
2
9
0
022-4596/01 $35.00
Copyright ( 2001 by Academic Press
All rights of reproduction in any form reserved.

3
0
A. BENSALEM
TABLE 1
X-ray Powder Di4raction Data of the As-Prepared Sample
TABLE 1=Continued
h
k
l
dꢀ"ꢁ (A
>
)
d#!ꢂ# (A
>
)
Iꢀ"ꢁ (%)
h
k
l
dꢀ"ꢁ (A
>
)
d#!ꢂ# (A
>
)
Iꢀ"ꢁ (%)
2
2
1
3
2
3
1
4
4
2
1
3
2
4
4
4
2
5
3
5
2
5
2
1
6
3
3
4
5
4
!2
2
!2
0
!2
1
2
!1
0
!2
!5
2
2.5271
2.4103
2.3521
2.2468
2.2027
2.1964
2.1045
2.0378
1.9877
1.9395
1.8946
1.8204
1.7737
1.6704
1.5843
2.5564
2.4144
2.3510
2.2781
2.2058
2.2002
2.1072
2.0468
1.9801
1.9256
1.9139
1.8235
1.7796
1.6639
1.5866
56
26
18
15
13
20
13
20
14
26
18
50
20
9
1
0
1
0
0
1
1
2
2
2
0
0
1
1
2
1
3
3
0
3
2
0
1
1
2
2
2
1
0
1
0
3
2
0
1
0
4
0
1
4
2
0
0
1
!1
0
8.0781
7.8931
6.9536
6.4771
5.4534
5.1216
4.8387
4.4624
4.2997
4.0452
4.0229
3.9860
3.6560
3.5477
3.2355
3.0426
2.9580
2.8590
2.7266
2.6666
2.6374
8.0126
7.8463
6.9419
6.5462
5.4437
5.0694
4.8288
4.4465
4.2103
4.0063
3.9868
3.9231
3.6260
3.4945
3.2470
3.0392
2.9435
2.8718
2.7218
2.6846
2.5975
12
25
10
57
14
13
20
26
58
32
33
24
19
11
93
100
63
14
10
12
21
1
0
1
!1
!1
0
1
2
3
!1
1
!3
!3
1
!1
!2
!2
2
11
As-prepared sample
Na Zn(HPO ) )4H O(10)
ꢁ
ꢂ ꢁ
ꢁ
a (A
b (A
c (A
>
b (3)
>
>
)
)
)
8.896(8)
13.092(5)
10.882(9)
115.760(6)
8.947(2)
13.254(2)
10.098(2)
116.358(6)
!1
2
FIG. 1. FTIR spectrum of the as-prepared sample.

NEW LAYERED LITHIUM ZINC PHOSPHATE HYDRATE
31
FIG. 2. DS-TG curve of the as-prepared sample.
RESULTS AND DISCUSSION
1630 cm\ꢀ and at 3250 cm\ꢀ are attributed respectively
to the water bending and stretching motions, while the band
The X-ray powder di!raction pattern and the corre- observed at 3450 cm\ꢀ and the small shoulder at about
sponding data indicate that the prepared solid is iso- 3600 cm\ꢀ are both assigned to H}O(P) stretching in
structural with Na Zn(HPO ) )4H O (Table 1). Using HPOꢁ\ ions. The absorption bands observed in 400}700
ꢁ
ꢂ ꢁ
ꢁ
ꢂ
a Scintag Indexing program, the XRD data were indexed in and 900}1250 cm\ꢀ are all assigned to the various vibration
a monoclinic cell. The least-squares re"nement of the in- modes of HPOꢁ\ ions.
ꢂ
dexed pattern gave a cell with dimensions a"8.896(8) A
b"13.092(5) A; c"10.882(9) A
cell dimensions are very similar to those of Na Zn(HPO ) ) sample and therefore suggest the empirical formula
>
;
X-ray data along with the IR observations con"rm the
>
>
, and b"115.760(6)3. These isostructurality with Na Zn(HPO ) )4H O of the prepared
ꢁ
ꢂ ꢁ
ꢁ
ꢁ
ꢂ ꢁ
H O. However, the c parameter of the prepared sample Li Zn(HPO ) )nH O. To con"rm the exact amount of
ꢂ ꢁ
water of hydration and also study the thermal stability
4
ꢁ
ꢁ
ꢁ
appears to be slightly larger.
The infrared spectrum of the as-prepared sample (Fig. 1) of the prepared sample, thermogravimetric analysis (TGA)
exhibits several OH vibrations. The bands observed at as well as di!erential scanning calorimetry (DSC) were

3
2
A. BENSALEM
FIG. 3. FTIR spectrum of the as-prepared sample heated at 2503C.
FIG. 4. FTIR spectrum of the as-prepared sample heated at 5003C.

NEW LAYERED LITHIUM ZINC PHOSPHATE HYDRATE
33
performed. The DS-TG curve (Fig. 2) exhibits three equations below:
endothermic e!ects corresponding to three weight losses.
3
ꢀ
ꢃꢆ !
Li Zn(HPO ) )0.66H O &&" Li Zn(HPO )
The "rst one occurs at around 1003C with a weight loss of
.5% followed by the second one at around 1503C with
ꢁ
ꢂ ꢁ ꢁ ꢁ ꢂ ꢁ
1
3
ꢁ
ꢂꢆ !
#
0.66H O &&" ꢀ+Zn P O ,#ꢀ+Li P O ),
a weight loss of 2.5%. The third weight loss of 4.5% is
observed at 2403C. No weight change is observed beyond
ꢁ
ꢁ
ꢁ ꢁ ꢄ ꢁ ꢂ ꢁ ꢄ
#H O
ꢁ
3
503C.
The total observed weight loss is 8.5%. The "rst two
ACKNOWLEDGMENTS
heat events can be attributed to the removal of water
molecules intercalated in the structure. In fact, the IR
spectra of the sample heated at 2003C show the disappear-
ance of the O}H vibration attributed to water molecules
The author gratefully acknowledges the support of the Provost Gale
Stevens Haynes for providing free housing at LIU campus for the summer
research interns and of the LIU research release time committee.
(
Fig. 3). The third weight loss, observed at 2403C, is at-
REFERENCES
tributed to the loss of water due to the dehydration of
HPOꢁ\ into P Oꢂ\ ions. The XRD data of the sample
ꢂ
ꢁ ꢄ
1
. J. M. Thomas, Philos. R. Soc. ¸ondon 333, 173 (1990).
heated at 5003C for 1 h shows that this HPOꢁ\}P Oꢂ\
ꢁ ꢄ
transformation leads to a mixed phase Zn P O (11)
ꢂ
2. J. M. Thomas, Sci. Am. 4, 112 (1992).
3
. J. M. Thomas and C. R. Theocharis, in &&Perspectives in catalysis,''
p. 465. Blackwell-IUPAC, 1992.
ꢁ
ꢁ ꢄ
Li P O (12). This is also con"rmed by the IR spectra of the
ꢂ ꢁ ꢄ
sample heated at 5003C (Fig. 4). Indeed, it shows the disap-
4. A. Bensalem and G. Iyer, J. Solid State Chem. 114, 598 (1995).
5
6
. A. Bensalem, G. Iyer, and S. Amar, Mat. Res. Bull. 30(12), 1471 (1995).
. A. Bensalem, Y. H. Ko, and T. V. Vijayaraghavan, Mater. Res. Bull.
pearance of all the absorptions within 4000}3000 cm\ꢀ and
distinct changes for all the absorptions in the 1400 to 400-
cm\ꢀ range. Thus, by attributing the third weight loss to the
3
2(11), 1473 (1997).
7
8
. P. B. Moore and J. Shen, Nature 306, 356 (1983).
. M. Estermann, L. B. Mc Casker, Ch. Baerlocher, A. Merrouche, and
H. Kessler, Nature 352, 320 (1991).
dehydration of HPOꢁ\ ions, we have used the "rst two
ꢂ
weight losses to estimate the amount of water molecules
9
. V. Soghomonian, Q. Chen, R. C. Haushalter, J. Zubieta, and
C. J. O'Connor, Science 259, 1596 (1993).
intercalated in the structure. The composition of the as-
prepared sample is then determined to be Li Zn(HPO ) )
ꢁ
ꢂ ꢁ
10. W. T. A. Harrison, T. M. Neno!, T. E. Gier, and G. D. Stucky, J. Solid
State Chem. 113, 168 (1994).
0
.66H O.
ꢁ
The structural changes due to two consecutive loss of
1
1. N. Selivanova, Russ. Inorg. Chem. 20, 327 (1995).
water by the prepared samples can be summarized in the 12. Tien and Hummel, J. Am. Ceram. Soc. 44, 206 (1961).