Study of Negative Thermal Expansion and Shift in Phase Transition
Temperature in Ti
4+
- and Sn
4+
-Substituted ZrW
2
O
8
Materials
Klaartje De Buysser,*
,²
Isabel Van Driessche,
²
Bart Vande Putte,
‡
Paul Vanhee,
‡
Joseph Schaubroeck,
‡
and Serge Hoste
²
Department of Inorganic and Physical Chemistry, Building S3 Ghent UniVersity Krijgslaan 281,
9000 Ghent, Belgium, and Faculty of Applied Engineering Sciences, UniVersity College Ghent,
Schoonmeersstraat 52, 9000 Ghent, Belgium
Received August 23, 2007
The negative-thermal-expansion material ZrW
2
O
8
is known to undergo an order-disorder phase transition which
affects its expansion behavior. In this study, Ti
4+
and Sn
4+
are examined as possible substituting ions for the Zr
4+
position in ZrW
2
O
8
. This substitution leads to a decrease in cell parameters, as the ionic radii of the substituents
are smaller than the Zr
4+
ionic radius. A remarkable decrease in transition temperature is noticed. DSC is used to
quantify the enthalpy and entropy changes during the phase transition in order to reveal the mechanisms behind
this decrease. It is shown that the strength of the M-O bond plays an important role, as it is a partner in the rigid
unit mode motion and the order-disorder transition mechanism.
Introduction
ZrW
2
O
8
is known as an isotropic negative-thermal-
expansion material in its entire kinetic stability range (-273
to 825 °C).
1
This behavior is in contrast with the asymmetry
of the vibrational potential well which leads to positive
thermal expansion in most solid materials. Contraction upon
heating is not exceptional among solids, as it can be seen
for example in tetrahedrally bonded crystals at low temper-
ature and -quartz at high temperatures.
2,3
ZrW
2
O
8
is formed by corner-linked ZrO
6
and WO
4
polyhedra which are connected by two-fold-coordinated
oxygen atoms. In the WO
4
tetrahedra, one oxygen atom
remains singly coordinated. The polyhedra are arranged in
an open-framework structure. RUMs, or rigid unit modes,
can occur within these polyhedra. These are low-energy
vibrations of the polyhedra without distortion of the intra-
hedral bond distances or angles. These RUMs have been
associated with a possible mechanism behind the large nega-
tive thermal expansion behavior exhibited by the ZrW
2
O
8
crystal structure.
4-10
The isotropy of the thermal expansion is caused by the
cubic crystal structure of R-ZrW
2
O
8
(P2
1
3) with WO
4
tetrahedra aligned along the [111] axis. ZrW
2
O
8
undergoes
an order-disorder transition at 150-160 °C from cubic R
to cubic (Pa3 h). The direction in which the WO
4
tetrahedra
point becomes dynamically disordered in the high-temper-
ature phase. The phase transition also affects the thermal
expansion coefficient, but the negative thermal expansion is
maintained: R-phase )-10 × 10
-6
°C
-1
and -phase )
-4 × 10
-6
°C
-1
.
11
The use of ZrW
2
O
8
to tailor the thermal expansion of
composite materials is described in the literature.
12-22
* To whom correspondence should be addressed. E-mail:
Klaartje.DeBuysser@Ugent.be.
²
Ghent University Krijgslaan.
‡
University College Ghent.
(1) Evans, J. S. O.; Mary, T. A.; Vogt, T.; Subramanian, M. A.; Sleight,
A. W. Chem. Mater. 1996, 8, 2809.
(2) Taylor, R. E. In Data series on material properties, 1st ed.; Ho, Y.,
Ed.; ASM International: Materials Park, OH, 1998.
(3) Callister, W. D. XXXXX, 5th ed.; Anderson, W., Ed.; Wiley and
Sons: Danvers, 2000; p 661.
(4) Barrera, G. D.; Bruno, J. A. O.; Barron, T. H. K.; Allan, N. L. J.
Phys.-Condens. Mat. 2005, 17, R217.
(5) Evans, J. S. O.; David, W. I. F.; Sleight, A. W. Acta Crystallogr. B
1999, 55, 333.
(6) Gallardo-Amores, J. M.; Amador, U.; Moran, E.; Alario-Franco, M.
A. Int. J. Inorg. Mater. 2000, 2, 123.
(7) Noailles, L. D.; Peng, H. H.; Starkovich, J.; Dunn, B. Chem. Mater.
2004, 16, 1252.
(8) Sleight, A. W. Inorg. Chem. 1998, 37, 2854.
(9) Allen, S.; Ward, R. J.; Hampson, M. R.; Gover, R. K. B.; Evans, J. S.
O. Acta Crystallogr. B 2004, 60, 32.
(10) Tao, J. Z.; Sleight, A. W. J. Solid State Chem. 2003, 173, 442.
(11) Mary, T. A.; Evans, J. S. O.; Vogt, T.; Sleight, A. W. Science 1996,
272, 90.
(12) Kofteros, M.; Rodriguez, S.; Tandon, V.; Murr, L. E. Scripta Mater.
2001, 45, 369.
(13) Yilmaz, S.; Dunand, D. C. Compos. Sci. Technol. 2004, 64, 1895.
Inorg. Chem. 2008, 47, 736-741
736 Inorganic Chemistry, Vol. 47, No. 2, 2008 10.1021/ic701660w CCC: $40.75 © 2008 American Chemical Society
Published on Web 12/21/2007