
ION
BEAM
INDUCED
GROWTH
STRUCTURE
OF
FLUORITE
TYPE
OXIDE
FILMS
FOR
BIAXIALLY
TEXTURED
HTSC
COATED
CONDUCTORS
Y.
IIJIMA,
M.
KIMURA, AND
T.
SAITOH
Fujikura
Ltd.,
1-5-1,
Kiba, Koto-ku,
Tokyo
135-8512,
JAPAN,
ABSTRACT
Biaxially
aligned
film
growth by dual-ion-beam
sputtering methods
were
studied
for
fluorite
type
(Zro.85Yo.15Oi.
93
(YSZ),
Hf
0
.
74
Yb
0
.
26
0
1
.
87
,
CeO
2
),
pyrochlore
type
(Zr
2
Sm
2
0
7
),
and
rare-earth
C
type
(Y
2
0
3
,
Sm
2
0
3
)
oxides
on
polycrystalline
Ni-based
alloy
substrates.
Cube-
textured
(all
axes
aligned
with
a
<100>
axis
substrate normal) films were
obtained for
fluorite
and
pyrochlore
ones
by
low
energy
(<300
eV)
ion bombardment
at
low
temperatures
(<
300
°C).
Besides,
cube
textured
Y
2
0
3
films
were
obtained
in
far
narrower conditions
with
a
quite
low
energy
(150
eV)-ion bombardment
at
the
temperature
of
300
TC.
The
assisting
ion
energy
dependence was
discussed
in
connection
with lattice
energies
for
these
oxide
crystals.
INTRODUCTION
Biaxially
aligned
Yttria
Stabilized
Zirconia
(YSZ)
or
MgO
films formed
by
ion-beam-
assisted
deposition
(IBAD)
are
reliable
template
layers
for
Y-123
coated
conductors
[1-4].
However,
intercalation
of
thin
CeO
2
or
Y
2
0
3
layers
beneath
Y-123
film
is
still
effective
to
compensate
lattice
mismatch
and
prevent slight interdiffusion
[5].
It
is
worthy to
form
more
adequate
buffer
materials
directly
on alloy tapes by IBAD.
In
this
work,
the crystalline
alignment
properties were
studied
for
fluorite type
(Zro.
85
Yo.1501.93
(YSZ),
Hfo.
74
Ybo.
26
0
1
.
87
,
CeO
2
),
pyrochlore
type
(Zr
2
Sm
2
0
7
),
and
rare-earth
C
type
(Y
2
0
3
,
Sm203)
oxide
films.
Those
three
type
crystals have
quite
similar structures.
Fig.
1
shows
a
schematic
view
of
the
fluorite structure. Pyrochlore
and
rare-earth
C
structures
correspond
to
ones whose
1/8
and
1/4
of
oxygen
ions
deleted
from
fluorite
structure,
respectively.
Comparison
of
growth
properties
between
them
would
help
to
understand
the
peculiar
crystallization
of
the
IBAD
process,
whose
mechanism
has
been
poorly
understood
as
yet.
This paper
concentrates
on fluorite-like
type
oxides
formed
by
using
a
dual-ion-beam-
sputtering
method.
IBAD
is
characterized
to
conduct concurrent
ion
bombardment
during
film growth,
which
induces
biaxially textured
crystallization
[6].
It
is
natural
to
consider
lattice-bonding
strength,
which
affects
ion bombardment
effects
on
growing films.
The
fluorite-like
type
oxides
are
ionic
crystals,
and
their
lattice
bonding
energies
are
evaluated
by static
electricity
among
cations
and
oxygen
ions. Lattice energies should
decrease
with
fluorite,
pyrochlore,
and
rare-
Fig.
1.
Schematic drawing
for
structure
of
fluorite
type oxide.
cation
0
02
45
Mat.
Res.
Soc.
Symp.
Proc.
Vol.
585
©
2000
Materials
Research Society