Page 55 - Book Hosokawa Nanoparticle Technology Handbook

FUNDAMENTALS CH. 1 BASIC PROPERTIES AND MEASURING METHODS OF NANOPARTICLES
On the other hand, few studies on the critical size [14] I.P. Batra, P. Wu´rfel and B.D. Silverman: Phys. Rev. B,
´
of the attractive and useful materials of lead zirconate 8, 3257 (1973).
titanate (PZT) family have been reported. In addition, [15] R. Kretschmer, K. Binder: Phys. Rev. B, 20, 1065
fabrication of bulk PZT single crystals for character- (1979).
ization is very hard, especially for the case of PZT [16] A.J. Bell, A.J. Moulson: Ferroelectrics, 54, 147 (1984).
with a morphotropic phase boundary (MPB; molar [17] B.D. Begg, E.R. Vance and J. Nowotny: J. Am. Ceram.
ratio of Zr to Ti is 53:47) composition which exhibits Soc., 77, 3186 (1994).
many excellent electrical properties such as
ferroelectric and piezoelectric properties. Therefore, [18] K. Ishikawa, T. Uemori: Phys. Rev.B, 60, 11841
many intrinsic data for the PZT materials with a (1999).
composition near MPB are basically insufficient [19] K. Ishikawa, K. Yoshikawa and N. Okada: Phys. Rev.
from the theoretical prospect. Furthermore, charac- B, 37, 5852 (1988).
terization techniques have not been established for [20] S. Chattopadhyay, P. Ayyub, V.R. Palkar and
the evaluation of the intrinsic properties of the solid M. Multani: Phys. Rev. B, 52, 13177 (1995).
solution system of PZT family. Recently, analytical [21] H. Suzuki, T. Ohno: J. Soc. Powder Technol., Jpn., 39
method to characterize the critical size and the (12), 877–884 (2002).
dielectric property for the ferroelectric nanoparticles
has been developed using Raman spectroscopy [21].
The critical size with which crystal symmetry of the 1.9 Surface characteristics
particles changes can be measured by this method.
The critical sizes of BT and PZT nanoparticles are
shown in Figs 1.8.3 and 1.8.4, respectively, together In microscopic view of an atomic level, a solid surface
with the particle size dependence of the Curie tem- is in an unsaturated state that the continuity of bonds is
perature at which crystal symmetry transforms from broken up. Atoms, ions or molecules constructing a
tetragonal to cubic. These figures clearly show that solid surface cannot diffuse, even if potential energy
the chemical composition, particle size and the resid- differs between adjacent ones, because the activation
ual stress in the nanoparticles can change the crystal energy required for surface diffusion is in general quite
structure of the nanoparticles. high, and hence homogenization of the surface cannot
be achieved as taking place on liquid surface. Due to
these two features, the solid surface shows unique char-
References acteristics that cannot be expected from bulk structure
of the solid. Especially for nanoparticles, the number of
[1] F.S. Galasso (ed.), M. Kato, N. Mizutani and
atoms, ions or molecules making up the particle
K Uematsu: Fain-seramikkusu no Kessyou-kagaku, becomes larger on the surface rather than within the
Agune-gijutusenta, ISBN;4-900041-01-7. particle. For this reason, a number of unique character-
[2] N. Claussen: J. Am. Ceram. Soc., 61 (1-2), 85–86 (1978). istics specific to nanoparticles appear [1, 2].
[3] S.Soumiya(ed.):Zirukonia-Seramikkusu, Uchidarou- These characteristics give strong effects not only to
kakuho, pp.109–125 (1983). quantum size effect specific to nanoparticles but also
[4] R.C Garvie: J. Phys. Chem., 69 (4), 1238–1243 (1965). to phenomena relating to powder handling such as
adhesion and coagulation [3]. Therefore, to understand
[5] J.E. Bailey, D. Lewis, Z.S.M. Librant and L.J. Porter:
and control the characteristics of the particle surface
Trans. J. Br. Ceram. Soc., 71, 25–30 (1972).
are often key technology for success in researches and
[6] E. Tani, M. Yoshimura and S. Somiya: J. Am. Ceram.
developments with regard to nanoparticles.
Soc., 66 (1), 11–14 (1983).
As described above, a solid surface newly formed is
[7] R.C. Gsrvie, R.H. Hannink and R.T. Pascoe: Nature, in a state that the bonds are broken up. For this reason,
258, 703 (1975). surface relaxations in various forms occur in order to
[8] T. Mitsuhashi, M. Ichihara and U. Tatsuke: J. Am. stabilize the surface. The relaxations depend on the
Ceram. Soc., 57, 97 (1974). type of chemical bond such as covalent, ionic or metal-
[9] C. Jaccard, W. Känzig and W. Peter: Helv. Phys. Acta, lic bond, and also on difference of materials. For con-
26, 521 (1953). venience, the relaxation involving chemical changes is
termed here as the chemical relaxation, and one with-
[10] W. Känzig, R. Sommerhalder: Helv. Phys. Acta, 26,
out the changes are termed as the physical relaxation,
603 (1953).
whereas the both relaxations take place simultaneously
[11] V. Kuleshov, M.G. Radchenko, V.D. Dudkevich and
in most cases. It is also desirable that nanoparticles are
Eu.G. Fesenko: Cryst. Res. Technol., 18, K56 (1983).
dealt with under atmospheric pressure in most indus-
[12] T. Kanata, T. Yoshikawa and K. Kubota: Solid State trial cases. In this case, surface relaxation due to
Commun., 62, 765 (1987). adsorption of atmospheric components occurs simulta-
´
[13] I.P. Batra, P. Wu´rfel and B.D. Silverman: Phys. Rev. neously as well. For this reason, stabilization due to the
Lett. 30, 384 (1973). adsorption will also be described in this section.
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