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Phase stability and defect structure determination of polytitanate compunds in the BaO-TiO2 system
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Phase stability and defect structure determination of polytitanate compunds in the BaO-TiO2 system
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http://www.ohsu.edu/xd/education/library/services/theses-dissertations/rights-statement.cfm
Title
Phase
stability
and
defect
structure
determination
of
polytitanate
compunds
in the
BaO-TiO2
system
Creator.PersonalName
Javadpour
,
Jafar
Thesis.Degree
Ph.D.
Thesis.Major
Materials Science and Engineering
Thesis.DateDegreeAwarded
January
1988
Institution
Oregon Graduate Center
Department
Dept. of Materials Science and Engineering
Thesis.Advisor/Mentor
Eror, Nicholas G.
Thesis.Committee
Wood, William E.
Devletian, Jack H.
Davis, Paul R.
Subject.LCSH
Dielectrics
Ceramic materials -- Defects
Barium titanate
Call Number
Q183.5.OGC J27 1988
Description.Abstract
Polytitanates
in the
BaO-
TiO2
system
with
Ba:Ti
ratios
ranging
from
1:2
to
1:5
were
prepared
using
a
low
temperature
technique
developed
by
Pechini
. The
samples
were
heated
at
600
to
1300°C
in
oxygen
.
Room
temperature
Raman
spectroscopy
was
used
to
investigate
the
phase
relations
in this
system
.
Results
of this
study
indicate
the
following
:
except
for
BaTi4O9
, the
powders
of these
compounds
were
amorphous
when
heated
at
600°C
for
4hrs
; the
compound
BaTi2O5
is
a
low
temperature
stable
phase
;
Ba6Ti17O40
forms
only
at
temperatures
above
1100°C
;
Ba4Ti13O30
does
not
form
below
1000°C
; the
single
phase
BaTi4O9
structure
was
observed
at
1200°C
'; the
Ba2Ti9O20
phase
is
obtained
only
after
long
heat
treatment
at
1200°
;
BaTi5O11
was
stable
up
to
1200°C
, at
which
it
decomposes
into
Ba2Ti4O20
and
TiO2
.
After
determination
of
stability
relationships
in this
system
, the
electrical
conductivities
of these
compounds
were
examined
as a
function
of
temperature
and
oxygen
partial
pressure
. For
all
the
temperatures
(850-1150°C)
studied
, the
conductivities
of these
compounds
increased
with
decreasing
oxygen
partial
pressure
resulting
in
n-type
properties
throughout
the
whole
P[subscript
O2]
range
(10[superscript
-19
-
1atm)
. The
P[subscript
O2]
dependencies
of the
electrical
conductivity
were
found
to be
linear
for an
extensive
range
of
oxygen
partial
pressures
. On the
basis
of
structural
considerations
the
conductivity
data
was
described
by a
majority
defect
model
consisting
of
both
singly
and
doubly
ionized
oxygen
vacancies
. For
lower
oxygen
partial
pressure
values
a
drastic
change
in the
electrical
conductivity
was
observed
. This
is
believed
to
result
from
increasing
defect
interaction
for
larger
departures
from
stoichiometry
. A
defect
model
based
on this
interaction
is
proposed
to
account
for the
observed
sharp
change
in the
electrical
conductivity
values
.
Language
eng
Type
Text
Format.Use
Needs Adobe Acrobat Reader to view.
Format.FileType
pdf
Format.FileSize
2371.42 KB
OCLC number
17642965
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