SYNTHESIS CONDITIONS AND THE OBTAINED PHASE OF ZIRCONIA
209
oxychloride with the nitrates follow the decomposition of composition of the transition metal precursor are determin-
the precursor alone. The regular formation of a gas shell, all ing elements for the nature of the phase obtained and for
along the decomposition of the oxychloride, would also some of its physico-chemical properties. For the latter(s) it
explain that the solid particles do not settle before complete might be the same, but, due to the presence of the liquid
transformation.
phase, the partial dissolution of the remaining zirconium
precursor cannot be set aside.
LiNO (s)#2HCl(g) P LiCl(s)#H O(g)
ꢃ
ꢂ
#
1/2Cl (g)#NO (g)
[11]
REFERENCES
ꢂ
ꢂ
As a con"rmation of this pathway, the ZrO powders are
very porous and develop large speci"c surface areas.
1
. A. Benedetti, G. Fagherazzi, and F. Pinna, J. Am. Chem. Soc. 72(3),
67}469 (1989).
2. R. Cypres, R. Wollast, and J. Rauq, Ber. Bent. Keram. 40(9), 527}532
1963).
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. V. Harle, J. P. Deloume, L. Mosoni, B. Durand, M. Vrinat, and
ꢂ
4
According to this pathway, the alkali metal ions must be
distributed mainly on the surface of crystallites of ca. 10 nm
in size. As the TGA curves do not depend on the alkali metal
nitrate, the di!erence of phase, according to the nature of
the alkali metal, is interpreted by taking into account their
ionic potential. The most polarizing one, the Li> ion, cre-
ates tensions on the surface of the particle which counteract
the size e!ect. The equilibrium bulk/surface is then dis-
placed toward the monoclinic phase. Powders containing
less than 10% of the tetragonal phase are obtained. As the
radius of the alkali metal increases, the polarizing power of
the ion decreases, and the cation-induced super"cial ten-
(
3
4
H
M. Breysse, Eur. J. Solid State Inorg. Chem. 31, 197}210 (1994).
. P. Afanasiev, Mater. ¸ett. 34, 253}256, (1998).
5
6. J. P. Deloume, J. P. Schar!, P. Marote, B. Durand, and A. Aboujalil,
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7
. R. Lyonnet, C. Ciaravino, P. Marote, J. P. Schar!, B. Durand, and
J. P. Deloume, High ¹emp. Mater. Processes 3(2), 269}278 (1999).
. D. H. Kerridge, in &&The chemistry of nonaqueous solvents''
8
(J. J. Lagowski, Ed.), Vol. VB, p. 269. Academic Press, New York,
1978.
9
. D. H. Kerridge and J. Cancela-Rey, J. Inorg. Nucl. Chem. 37, 405
(
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1. J. L. Tosan, Ph.D. These, Universite Claude Bernard Lyon 1, no. 125,
991.
sions are weakened. The powders obtained using NaNO or
ꢃ
KNO contain about 40% of the tetragonal phase. An
ꢃ
1
`
H
experiment carried out with caesium nitrate corroborates
1
that, in the obtained zirconia, the tetragonal phase is largely 12. M. Jebrouni, B. Durand, and M. Roubin, Ann. Chim. Fr. 16, 569}579
1991).
(
predominant.
1
3. H. Toraya, M. Yoshimura, and S. Somiya, J. Am. Ceram. Soc. 67(6),
C119}121 (1984).
IV. CONCLUSION
1
1
4. P. Afanasiev and C. Geantet, Mater. Chem. Phys. 41, 18}27 (1995).
5. Th. Pro!en, R.B. Neder, and F. Frey, Acta Cryst. B 52, 59 (1996).
The transformation of a zirconium salt in the correspond- 16. H. Nishizawa, N. Yamasaki, K. Matsuoka, and H. Mitsushio, J. Am.
Ceram. Soc. 65, 343 (1982).
7. G. Tilloca, J. Mater. Sci. 30, 1884 (1995).
8. A. Benamira, Ph.D. Thesis no. 304, Universite
France, 1997.
9. &&Handbook of Chemistry and Physics,'' 76th ed. (D. R. Lide, Ed.).
CRC Press, Boca Raton, FL, 1995}1996.
ing oxide by reaction with an excess of an alkali metal
1
1
nitrate involves a multistep reaction, the "rst one(s) occur-
ring in the solid state, before the melting of the nitrates, and
the last one(s) above the melting point. For the former(s)
which represent(s) 80% of the reaction, the structure and the
H Claude Bernard Lyon 1,
1
Marote, Pedro
