Page 255 - Book Hosokawa Nanoparticle Technology Handbook

FUNDAMENTALS CH. 4 CONTROL OF NANOSTRUCTURE OF MATERIALS
[2] A. Inoue, J. Fukuta, Y. Matano and Y. Matsumoto:
J. Ceram. Soc. Jpn., 100(2), 208–210 (1992).
[3] K. Kageyama, M. Enoki, T. Kishi, K. Ikuina and
M. Kimura: J. Jpn. Inst. Metals (in Japanese), 57(7),
756–760 (1993).

4.5.3 Nanostructure control of a joined interface
A joined interface plays an important role to reveal
high functionalities of materials including composite
materials and electronic devices.
It is a very important issue to clarify mechanism of
revealing of high functionalities and to control high
functionalities at the joined interface. Remarkable pro-
gresses of measurement, evaluation, and analytical
technology at atomistic level have been performed by
progresses of quantum beam technologies such as an
electron beam, a laser beam, and a synchrotron radia-
tion, a nanoscale analytical technology and a simula-
Figure 4.5.13
Microstructure of LTCC of the Al O -glass-anorthite system. tion method by a first principle molecular dynamics.
2
3
Economos et al. reported more than 40 years ago
that 4 types of joined interfaces between oxides and
The existence of an anorthite layer of thickness metals, which are (1) a new phase is formed at the
1–2
m around the Al O particles, as schematically interface, (2) a ceramics is chemically attacked by
2
3
shown in Fig. 4.5.12, can be confirmed by observation metal, (3) a metal penetrates along with grain bound-
of the microstructure of the sintered material of Al O 3 aries of ceramics and (4) a reaction zone is not
2
particles and glass. Energy dispersive X-ray analysis observed at the interface, are observed by an optical
(EDX) reveals that the white particles, dark gray parts, microscope [1]. But, progress of analytical and char-
and light gray layer around the particles are regarded acterization technologies of interfaces revealed that
as Al O particles, glass, and the anorthite, respec- joined interfaces cannot be classified into simple cat-
2
3
tively. Presumably the anorthite crystal emerges after egories and formation of interface is affected by many
the reaction of the submicron Al O particles with the factors such as a joining time, an atmosphere, and a
3
2
glass. Subsequently the lack of difference in the reac- temperature. This has already been suggested by the
tive sintering performance within the nanosized region study of wettability of Al O by liquid Ni [2].
2
3
is considered to have a significant influence on the Many researchers have conducted direct observa-
structure of the final board and sintering control in a tions and simulations of joined interface between
further finer region is required in future. metal and ceramics. Especially, the interface structure
As mentioned above, the LTCC of the glass phase between Nb and Al O have been studied as a model
3
2
system shows different properties, depending upon the system, since thermal expansion coefficient of Nb is
microstructure of ceramics and glass, like an aggre- similar to that of Al O .The interface have been sys-
3
2
gate or generated crystal, even if the composition is tematically investigated by using Al O single crystal
2
3
the same. To create a dense structure, for which the which has different crystal orientation and by using
sintering in glass liquid phase plays a significant role, samples made by a solid phase joining, an internal
the elucidation of the crystallization mechanism and oxidation and a molecular beam epitaxial (MBE)
the control of the microstructure under a firing condi- methods [2–4]. It has been revealed that Nb and Al O
2
tion suitable for the electrode materials are needed, as is directly joined without a formation of reaction layer 3
well as the densification. Above all, in order to acquire and interface structures depend on a crystal orienta-
excellent electric properties, the microstructure and tion of Al O and joining method [5]. An information
2
3
crystal need to be controlled more precisely, which of bonding status between Nb and Al O has also been
2
3
requires technical advancement in the control of pow- obtained by X-ray photo-emission spectroscopy
der properties from submicron to nanosized range and (XPS) [6, 7]. Electrons in Nb atoms migrate to oxy-
the firing process in future.
gen atoms that are the components of Al O . The
3
2
results obtained by XPS are in good agreement with
References simulation result by Yamamoto et al. [8, 9].
When joined interfaces between dissimilar materi-
[1] Electronic Materials Manufacturers Association of als such as metal–ceramics systems are in an epitax-
Japan: Denshikairoyou koukinou seramikku kiban (in ial relationship, one of the important factors which
Japanese, Advanced Ceramic Board for Electric affect interface characteristics is a lattice mismatch-
Circuit), Japan Industrial Publishing Co., Ltd., (1994). ing. An interface structure is considerably affected by
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