Transformations of ruddlesden-popper oxides to new layered perovskite oxides by metathesis reactions

Article abstract of DOI:10.1021/ja9914644

We report transformations of the Ruddlesden-Popper (R-P) oxide, K₂La₂Ti₃O₁₀, to layered perovskite oxides, (Bi₂O₂)La₂Ti₃O₁₀, MLa₂Ti₃O₁₀ (M = Pb, Ba, Sr), and (VO)La₂Ti₃O₁₀, by a novel metathesis reaction with BiOCl, MCl₂, and VOSO₄·3H₂O, respectively. The formation of (VO)La₂Ti₃O₁₀, which occurs in aqueous medium around 100°C, suggests that the reaction is most likely topotactic, where the structural integrity of the perovskite sheet is preserved. We believe that the method described here provides a new general route for the synthesis/assembly of layered perovskite materials containing MX/M₂X₂ sheets, as indeed shown by the independent report of (CuX)LaNb₂O₇ synthesis by a similar reaction.

Full text of DOI:10.1021/ja9914644

J. Am. Chem. Soc. 2000, 122, 6237-6241
6237
Transformations of Ruddlesden-Popper Oxides to New Layered
Perovskite Oxides by Metathesis Reactions
,†
†
†
†
‡
J. Gopalakrishnan,* T. Sivakumar, K. Ramesha, V. Thangadurai, and G. N. Subbanna
Contribution from the Solid State and Structural Chemistry Unit and Materials Research Centre,
Indian Institute of Science, Bangalore-560 012, India
ReceiVed May 4, 1999. ReVised Manuscript ReceiVed January 27, 2000
Abstract: We report transformations of the Ruddlesden-Popper (R-P) oxide, K2La2Ti3O10, to layered
perovskite oxides, (Bi2O2)La2Ti3O10, MLa2Ti3O10 (M ) Pb, Ba, Sr), and (VO)La2Ti3O10, by a novel metathesis
reaction with BiOCl, MCl2, and VOSO4‚3H2O, respectively. The formation of (VO)La2Ti3O10, which occurs
in aqueous medium around 100 °C, suggests that the reaction is most likely topotactic, where the structural
integrity of the perovskite sheet is preserved. We believe that the method described here provides a new
general route for the synthesis/assembly of layered perovskite materials containing MX/M2X2 sheets, as indeed
shown by the independent report of (CuX)LaNb2O7 synthesis by a similar reaction.
Introduction
between the perovskite sheets. Accordingly, we expected that
R-P phases such as K2La2Ti3O10 and K2SrTa2O7 could be
transformed to other layered perovskites such as the A phases
in metathetical reactions of the kind
Among the several lamellar materials derived from the
1
perovskite (CaTiO3 ) ABO3) structure, the Ruddlesden-
2
′
Popper (R-P) phases, A2[A n-1BnO3n+1], and the Aurivillius
3
(
A) phases, (Bi2O2)[An-1BnO3n+1], are widely investigated for
4
′
K [A B O3n+1] + 2BiOCl f
several materials properties. The perovskite sheet, [An-1BnO3n+1],
which may be thought of as derived by slicing the three-
dimensional (3-D) perovskite structure along one of the cubic
directions, is common for both series of oxides. Sr2TiO4,
Sr3Ti2O7, and Sr4Ti3O10 are representative members of the R-P
series and Bi2WO6, Bi2SrTa2O9, and Bi4Ti3O12 are typical
members of the A family. Members of the R-P family such as
K2La2Ti3O10 (n ) 3) and K2SrTa2O7 (n ) 2) containing alkali
2
n-1 n
(Bi O )[A B O3n+1] + 2KCl (1)
2
2
n-1 n
Indeed the reaction occurs around 800-900 °C transforming
both R-P phases to the corresponding A phases, Bi2La2Ti3O12
and Bi2SrTa2O9, in near-quantitative yields.
Having succeeded in the R-P f A transformation, we ex-
plored the synthesis of new layered perovskites by this strategy.
We could prepare several MLa2Ti3O10 (M ) Pb, Ba, Sr) and,
more importantly, a novel layered perovskite (VO)La2Ti3O10
in similar metathetical reactions with MCl2 and VOSO4‚3H2O,
respectively. While the formation of MLn2Ti3O10 phases (A )
5,6
cations between perovskite sheets exhibit an interlayer reactiv-
+
+
ity (K /H exchange) that suggests that the alkali cations are
weakly bound to the perovskite sheets in these materials. A
similar reactivity is not exhibited by R-P phases such as
Sr4Ti3O10 and Sr3Ti2O7 containing divalent (Sr2 ) cations
+
7
,8
alkali, Ln ) rare earth) has been reported already, a layered
2
+
*
To whom correspondence should be addressed.
Solid State and Structural Chemistry Unit.
Materials Research Centre.
perovskite containing interlayer (VO) cation has not been
reported. The facile formation of (VO)La2Ti3O10 in aqueous
medium around 100 °C suggests that the transformation,
K2La2Ti3O10 f (VO)La2Ti3O10, is most likely topotactic,
†
‡
(1) (a) Tilley, R. J. D. In Chemical Physics of Solids and Their Surfaces;
The Royal Society of Chemistry: London, 1980; Vol. 8, pp 149-160. (b)
Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Clarendon Press:
Oxford, 1984.
+
replacing the weakly bound interlayer K ions in the R-P phase
2
+
by the (VO) oxocation. We believe that the metathesis
reactions reported here provide a novel route for the assembly
of new layered perovskites containing MX/M2X2 sheets, includ-
ing the technologically important A phases, which find applica-
(
2) Ruddlesden, S. N.; Popper, P. Acta Crystallogr. 1957, 10, 538-539.
Ruddlesden, S. N.; Popper, P. Acta Crystallogr. 1958, 11, 54-55.
3) Aurivillius, B. Ark. Kemi 1949, 1, 463-480. Aurivillius, B. Ark. Kemi
950, 2, 519-527.
4) (a) Metallicity and superconductivity: Bednorz, J. G.; M u¨ ller, K. A.
(
1
(
4f,9
tion in ferroelectric nonvolatile memory devices. Indeed after
the present work was submitted for publication, Kodenkandath
Z. Phys. B. 1986, 64, 189-193. Fukuoka, H.; Isami, T.; Yamanaka, S. Chem.
Lett. 1997, 8, 703-704. Armstrong, A. R.; Anderson, P. A. Inorg. Chem.
1
994, 33, 4366-4369. (b) Magnetism and colossal magnetoresistance:
10
et al. reported the synthesis of (CuX)LaNb2O7 in a similar
Moritomo, Y.; Asamitsu, A.; Kuwahara, H.; Tokura, Y. Nature 1996, 380,
41-144. (c) Photocatalytic activity: Takata, T.; Furumi, Y.; Shinohara,
K.; Tanaka, A.; Hara, M.; Kondo, J. N.; Domen, K. Chem. Mater. 1997, 9,
reaction between KLaNb2O7 and CuX2 (X ) Cl, Br).
1
1
063-1064. (d) Dielectric properties, see: Frit, B.; Mercurio, J. P. J. Alloys
(7) Gondrand, M.; Joubert, J.-C. ReV. Chem. Miner. 1987, 24, 33-41.
(8) Schaak, R. E.; Mallouk T. E. J. Am. Chem. Soc. 2000, 122, 2798-
2803.
(9) Park, B. H.; Kang, B. S.; Bu, S. D.; Noh, T. W.; Lee, J.; Jo, W.
Nature 1999, 401, 682-684.
(10) Kodenkandath, T. A.; Lalena, J. N.; Zhou, W. L.; Carpenter, E. E.;
Sangregorio, C.; Falster, A. U.; Simmons, W. B., Jr.; O’Connor, C. J.; Wiley,
J. B. J. Am. Chem. Soc. 1999, 121, 10743-10746.
and Compounds 1992, 188, 27-35. (e) Ionic conductivity: Kendall, K.
R.; Navas, C.; Thomas, J. K.; zur Loye, H.-C. Chem. Mater. 1996, 8, 642-
6
49. (f) Ferroelectric memory device: Paz de Araujo, C. A.; Cuchiaro, J.
D.; McMillan, L. D.; Scott, M. C.; Scott, J. F. Nature 1995, 374, 627-
6
29.
(5) Gopalakrishnan, J.; Bhat, V. Inorg. Chem. 1987, 26, 4299-4301.
6) Ollivier, P. J.; Mallouk, T. E. Chem. Mater. 1998, 10, 2585-2587.
(
1
0.1021/ja9914644 CCC: $19.00 © 2000 American Chemical Society
Published on Web 06/17/2000

6
238 J. Am. Chem. Soc., Vol. 122, No. 26, 2000
Experimental Section
2 7
Synthesis. K La Ti O were prepared
Gopalakrishnan et al.
2
2
3
O
10, K
2
,6,11
SrTa
2 7
O
, and KLaNb
Ti 10 (10 mmol) was prepared
, La (predried at 900
5
as reported in the literature.
by reacting stoichiometric quantities of KNO
2
K La
2
3
O
3
2 3
O
°
C), and TiO
2
at 1000 °C for 2 days with one intermediate grinding.
Excess KNO
3
(25 mol %) was added to compensate for the loss due to
volatilization. After the reaction, the product was washed with distilled
water and dried in air at 200 °C. KLaNb was prepared similarly at
100 °C and the washed product was dried at 110 °C in air. K SrTa
was obtained from reaction of stoichiometric quantities of KNO
SrCO , and Ta with a 200% molar excess of KNO at 1050 °C for
2 h and 1150 °C for 24 h in air with intermediate grindings. The
washed product was dried in air at 450 °C. BiOCl was obtained by
reacting Bi with hot 3 N HCl followed by hydrolysis with excess
water. PbBiO Cl was prepared by reacting BiOCl and red PbO at
70 °C for 36 h in air.13 Blue crystals of VOSO
‚3H O were obtained
by passing SO into a suspension of V in concentrated H SO as
described in the literature.
Reaction between K La
2 7
O
1
2
2 7
O
3
,
3
O
2 5
3
1
2
O
3
1
2
2
6
4
2
2
2
O
5
2
4
1
4
2
2 3 2 2 7
Ti O10/K SrTa O and BiOCl in the solid
state was investigated by heating stoichiometric mixtures of the reactants
at various temperatures and duration in air. Examination of the products
by powder X-ray diffraction (XRD) revealed that the reaction occurred
according to eq 1 around 800-900 °C forming A-type phases and KCl
as products. With K
after 9 h, while with K
atures (900 °C for 6 h).
Reaction of K La Ti
occur at 600 °C for M ) Pb (flowing nitrogen, 48 h) and 750 °C (air,
2
La
2
Ti
3
O10, the reaction was complete at 810 °C
2
SrTa
2 7
O , the reaction required higher temper-
2
2
3 2
O10 with MCl (M ) Pb, Ba, Sr) was found to
1
3
K
2 h) for M ) Ba, Sr. The reaction between K
O readily occurred in aqueous medium. A sample of 1 mmol of
La Ti 10 and 1.5 mmol of VOSO ‚3H O in 100 mL of distilled
2 2 3 4
La Ti O10 and VOSO ‚
H
2
2
2
3
O
4
2
water was refluxed. The reaction was found to be complete in 5 days
as judged by EDS analysis and XRD of the product. The solid products
in all cases were washed with distilled water and dried in air at 100 °C
(
at room temperature and 150 °C for (VO)La
Characterization. Analyses of chemical composition were carried
out by energy-dispersive X-ray spectroscopy (EDS) using a JEOL JSM
40-A scanning electron microscope equipped with an EDAX micro-
2 3
Ti O10).
8
analytical system. Structural characterization was made by powder XRD
using a Siemens D-5005 powder diffractometer (Cu KR radiation). Unit
cell parameters were least-squares refined by the PROSZKI15 program.
Powder XRD intensities were calculated in select cases using the LAZY
1
5
PULVERIX program. Electron diffraction (ED) patterns of Bi
2 2
La -
Ti 12 were recorded using a JEOL JEM 200-CX transmission electron
3
O
microscope, and infrared spectra were recorded in KBr pellets using a
Perkin-Elmer FTIR spectrometer, model 1000 D.
Results and Discussion
Figure 1. Powder XRD patterns of (a) K
2
La
2
Ti
3
O
10, (b) Bi
2 2 3 12
La Ti O
The XRD pattern (Figure 1) of product 1 obtained from the
obtained from part a, (c) K
part c.
2 2 7
SrTa O , and (d) Bi
2
SrTa O
2 9
obtained from
reaction between K2La2Ti3O10 and BiOCl is closely similar to
1
6
that of Bi4Ti3O12 and is indexable on an orthorhombic cell
with a ) 5.441(1) Å, b ) 5.399(1) Å, and c ) 32.944(4) Å.
Similarly, the XRD pattern of product 2 obtained from the
reaction between K2SrTa2O7 and BiOCl could be indexed on
an orthorhombic cell with a ) 5.531(1) Å, b ) 5.535(1) Å,
and c ) 24.965(5) Å, the data being in close agreement with
phase to the A phase, corresponding to the replacement of
+
2+
interlayer K ions by [Bi2O2] units. EDS analyses of both
products show the expected metal atom ratios and the absence
of K. For product 1, we have calculated powder XRD intensities
assuming the structure of Bi4Ti3O12 (space group B2cb),18 where
Bi(1) are replaced by La. A comparison of the calculated and
observed XRD intensities (Table 1) reveals that the structure
of product 1 is indeed similar to that of Bi4Ti3O12, where Bi
atoms in the perovskite sheets are replaced by La. Electron
diffraction (ED) and lattice images provide further support to
the formation of A phases; for product 1 (Figure 2), we see
clearly a ca. 5.5 × 5.5 Å cell in the a-b plane with a repeat of
ca. 16.4 Å in the c direction, which is consistent with the powder
XRD data. Accordingly, we formulate reaction products 1 and
1
7
the values reported for Bi2SrTa2O9 in the literature. In both
cases, the c axis expands by ca. 3.2 Å in going from the R-P
(
11) Gopalakrishnan, J.; Bhat, V.; Raveau, B. Mater. Res. Bull. 1987,
2, 413-417.
12) Brauer, G. Handbook of PreparatiVe Inorganic Chemistry; Academic
2
(
Press: New York, 1963; Vol. 1, pp 622-623.
(
(
13) Ketteres, J.; Kramer, V. Mater. Res. Bull. 1985, 20, 1031-1036.
14) Brauer, G. Handbook of PreparatiVe Inorganic Chemistry; Academic
Press: New York, 1965; Vol. 2, pp 1285-1286.
(
38.
15) Losocha, W.; Lewinski, K. J. Appl. Crystallogr. 1994, 27, 437-
4
(
(
16) JCPDS File No. 35-0795.
17) Rae, A. D.; Thompson, J. G.; Withers, R. L. Acta Crystallogr. 1992,
(18) Dorrian, J. F.; Newnham, R. E.; Smith, D. K.; Kay, M. I.
B48, 418-428.
Ferroelectrics 1971, 3, 17-27.

Transformations of Ruddlesden-Popper Oxides
J. Am. Chem. Soc., Vol. 122, No. 26, 2000 6239
2 2 3
Table 1. X-ray Powder Diffraction Data for Bi La Ti O12 (1)
a
b
h
k
l
d
obs(Å)
d
cal (Å)
I
obs
I
cal
0
0
0
0
1
1
0
1
0
0
0
0
1
0
0
0
0
1
1
0
1
0
2
2
2
11
2
4
6
8
1
3
10
7
12
0
4
16.532
8.239
5.487
4.119
3.794
3.610
3.302
2.967
2.746
2.702
2.567
2.422
16.472
8.236
5.491
4.118
3.806
3.618
3.294
2.972
2.745
2.700
2.565
2.422
2.359
31
11
14
6
10
4
14
100
6
30
10
7
4
13
7
15
100
4
39
3
4
35
3
4
6
1
4
2.352
19
0
0
1
0
0
0
2
2
0
2
2
0
2
1
2
0
2
2
2
0
2
0
14
8
13
10
16
12
0
4
18
6
2.353
2.258
2.114
2.088
2.058
1.925
1.916
1.866
1.830
1.809
1.779
12
17
2
1
1
7
21
2
1
2
2.259
2.113
2.088
2.059
1.926
1.912
1.863
1.830
1.805
17
4
1
2
7
22
2
2
2
14
10
1.777
22
0
1
1
2
2
1
1
2
0
0
2
1
1
2
0
2
1
1
1
2
3
1
2
2
0
2
1
3
2
4
14
17
3
14
10
7
19
12
18
22
14
21
13
16
0
1.774
1.729
1.706
1.690
1.656
1.606
1.580
1.571
1.515
1.497
1.485
1.452
1.417
1.402
1.350
10
3
2
1
3
34
5
3
1
1
11
9
1
1
7
1.729
1.706
1.691
1.654
1.607
1.579
1.570
1.515
1.496
1.484
1.453
1.417
1.402
1.350
3
2
1
4
26
5
3
1
1
9
8
2
1
6
a
a ) 5.441(1) Å, b ) 5.399(1) Å, c ) 32.944(4) Å. b Intensities
are calculated by LAZY PULVERIX using the atomic coordinates of
Bi
4
Ti
3
O
12 where Bi(1) is replaced by La (ref 18).
Figure 2. (a) Electron diffraction (ED) pattern of Bi
an ca. 5.5 × 5.5 Å cell in the a-b plane. (b) Lattice image of Bi
Ti 12 showing an ca. 16.4 Å repeat along the c direction. The inset
shows the corresponding ED pattern.
2
La
2
Ti
3
O
12 showing
2
La
2
-
2
as Bi2La2Ti3O12 and Bi2SrTa2O9, respectively, having been
3
O
formed in the metathetical reactions 2 and 3.
orthorhombic (M ) Ba) or monoclinic (M ) Pb, Sr) systems.
The lattice parameters are listed in Table 2. The orthorhombic
lattice parameters of the M ) Ba phase are in agreement with
K La Ti O + 2BiOCl f (Bi O )La Ti O + 2KCl (2)
2
2
3
10
2
2
2
3
10
K SrTa O + 2BiOCl f (Bi O )SrTa O + 2KCl (3)
2
2
7
2
2
2
7
2
0
the values reported in the literature for BaLa2Ti3O10. The
monoclinic M ) Pb, Sr phases have not been reported to our
knowledge. In view of the close similarity of the powder XRD
patterns and lattice parameters of MLa2Ti3O10 (M ) Pb, Sr) to
In Figure 3, we show schematically the transformation of
K2La2Ti3O10 to Bi2La2Ti3O12. In a similar reaction between
KLaNb2O7 and PbBiO2Cl at 810 °C for 9 h, we could prepare
another layered perovskite of the formula (PbBiO2)LaNb2O7
2
1
those of BaNd2Ti3O10, we believe that the MLa2Ti3O10
members are isotypic with BaNd2Ti3O10 consisting of triple
+
+
indicating that (PbBiO2) could replace the K in KLaNb2O7
in between the perovskite sheets.
2
+
perovskite sheets interleaved by large M ions.
We have prepared a novel layered perovskite (VO)La2Ti3O10
in the following reaction.
We investigated the applicability of the metathesis route for
the synthesis of other layered perovskites. Thus we could
1
9
synthesize MLa2Ti3O10 Dion-Jacobson (D-J) phases for M
Pb, Ba, Sr in a reaction between K2La2Ti3O10 and MCl2.
Similar transformations of R-P phases to D-J phases with other
K La Ti O + VOSO ‚3H O f
2
2
3
10
4
2
)
(
VO)La Ti O + K SO + 3H O (4)
2 3 10 2 4 2
7
,8
rare-earth and M cations have been reported in the literature.
Powder XRD patterns of MLa2Ti3O10 could be indexed on
Interestingly, the reaction occurs in aqueous medium under
reflux (∼100 °C). As-prepared material (dried in air at room
(20) Guha, J. P. J. Am. Ceram. Soc. 1991, 74, 878-880; JCPDS file
No. 42-0418.
(21) Olsen, A.; Roth, R. S. J. Solid State Chem. 1985, 60, 347-357.
(19) (a) Dion, M.; Ganne, M.; Tournoux, M. Mater. Res. Bull. 1981,
1
6, 1429-1435. (b) Dion, M.; Ganne, M.; Tournoux, M.; Ravez, J. ReV.
Chim. Miner. 1984, 21, 92-103. (c) Jacobson, A. J.; Johnson, J. W.;
Lewandowski, J. T. Inorg. Chem. 1985, 24, 3727-3729.

6240 J. Am. Chem. Soc., Vol. 122, No. 26, 2000
Gopalakrishnan et al.
Figure 4. Powder XRD patterns of (a) (VO)La
VO)La Ti
2
Ti
3
2
O10‚H O and (b)
(
2
3 10
O .
mainly 00l reflections in the XRD pattern, which could also be
indexed on a tetragonal cell of approximate lattice parameters
a ) 3.82 Å and c ) 29.46 Å. As compared to the lattice
parameters of the parent K2La2Ti3O10 [a ) 3.8769(1) Å and c
)
29.824(1) Å], there is a considerable decrease (∼2.15 Å) in
the c parameter of anhydrous (VO)La2Ti3O10, which is consistent
+
with the replacement of the two larger K ions (ionic radius
Figure 3. Schematic representation of the metathetical reaction between
La Ti 10 (left) and BiOCl yielding Bi La Ti 12 (right) showing
replacement of interlayer K by (Bi sheets.
2+
1.55 Å in 9-coordination) by the smaller (VdO) cation (bond
K
2
2
3
O
2
2+
2
3
O
22
distance ∼1.63 Å) in the interlayer space. The presence of a
+
2 2
O )
-1
strong infrared absorption around 1010 cm which is charac-
2
+
23
teristic of the (VdO) stretch both in the hydrated and
anhydrous materials and the near absence of K in the EDS
together with the V:La:Ti atomic ratio of 0.98:2:3 (expected
ratio for stioichiometric (VO)La2Ti3O10 is 1:2:3) clearly reveals
that the metathesis reaction proceeds according to eq 4, yielding
a new layered perovskite (VO)La2Ti3O10.
Table 2. Lattice Parameters of Layered Perovskites
compd
crystal system
orthorhombic
unit cell parameters (Å)
(
(
(
Bi
2
2
O
2
)La
2
Ti
3
O
10
a ) 5.441(1)
b ) 5.399(1)
c ) 32.944(4)
a ) 5.531(1)
b ) 5.535(1)
c ) 24.965(5)
a ) 3.896(1)
b ) 25.54(1)
a ) 7.683(7)
b ) 7.651(3)
c ) 14.48(1)
â ) 97.8(1)°
a ) 7.669(1)
b ) 28.616(3)
c ) 3.869(1)
a ) 7.841(2)
b ) 7.641(2)
c ) 14.171(9)
â ) 100.8(1)°
a ) 3.809(2)
c ) 27.65(1)
Bi
O
2
)SrTa
2
O
7
orthorhombic
While the metathesis reactions with BiOCl, PbBiO2Cl, and
MCl2 which occur at considerably high temperatures (600-
PbBiO
2
)LaNb
2
O
7
tetragonal
9
00 °C) are not likely topotactic, the facile occurrence of
reaction 4 in aqueous medium around ∼100 °C suggests that it
is most likely topotactic, where the integrity of the perovskite
sheets is preserved during the chemical transformation. Further
work is essential to establish the actual structure of (VO)La2-
Ti3O10 and the topotactic nature of reaction 4.
PbLa
2
Ti
O
3 10
monoclinic
BaLa
2
Ti
3
O
10
orthorhombic
monoclinic
Conclusion
2 3 10
SrLa Ti O
While metathesis reactions involving exchange of atomic/
ionic species between the reactants are well-known in solid-
2
4
5
state chemistry, for example MoCl5 + /2Na2S f MoS2 +
(VO)La
2
Ti
3
O
10
tetragonal
1
5NaCl + /2S, the metathesis reported here is unique in that it
involves replacement of interlayer alkali cations in R-P phases
by structural entities such as (Bi2O2) , (PbBiO2) , and (VO) .
The formation of (VO)La2Ti3O10 is particularly significant since
2+
+
2+
temperature) is monohydrate (as revealed by thermogravimetry).
The water of hydration is lost around 150 °C giving a green
crystalline product whose powder XRD pattern (Figure 4) could
be indexed on a tetragonal cell with a ) 3.809(2) Å and c )
7.65(1) Å. As compared to the anhydrous (VO)La2Ti3O10, the
hydrated material is rather poorly crystalline showing broad,
(22) Longo J. M.; Arnott, R. J. J. Solid State Chem. 1970, 1, 394-398.
(
23) Nakamoto, K. Infrared Spectra of Inorganic and Coordination
Compounds, 2nd ed.; Wiley-Interscience: New York, 1970; p 114.
24) (a) Wiley, J. B.; Kaner, R. B. Science 1992, 255, 1093-1097. (b)
Gillan, E. G.; Kaner, R. B. Chem. Mater. 1996, 8, 333-343.
2
(

Transformations of Ruddlesden-Popper Oxides
J. Am. Chem. Soc., Vol. 122, No. 26, 2000 6241
it occurs at ∼100 °C in aqueous medium. We believe the
significance of the present work goes beyond the transformation
of R-P phases reported here; the strategy could in principle be
extended to the synthesis/assembly of novel layered materials
containing dimensionally compatible [MX] /[M2X2] layered
units, as indeed is shown by the recent synthesis of (CuX)-
LaNb2O7 by Kodenkandath et al.10
97), for financial support. We also thank Professor K. Ven-
katesan for helpful discussions on the crystal structure of
Bi Ti O .
4
3
12
n+
n+
Supporting Information Available: Powder XRD data for
PbBiO2)LaNb2O7 and MLa2Ti3O10 (M ) Ba, Sr, Pb) (PDB).
(
This material is available free of charge via the Internet at
http://pubs.acs.org.
Acknowledgment. We thank the Department of Science and
Technology, Government of India (Project No. SP/S1/H-17/
JA9914644