EFFECT OF LITHIUM FLUORIDE
ON THE DIELECTRIC PROPERTIES
OF BARIUM TITANATE
(http://perso.usthb.dz/~lbenziada)
IUPAC 9th International Conference on Novel Materials and Synthesis (NMS – IX)
October 17 – 22 , 2013, Shanghai, CHINA
SUMMARY
• Introduction
• Experimental procedures
• Results and discussion
• Conclusion
• References
INTRODUCTION
INTEREST FOR MATERIALS
have always represented an essential aspect of
.
• Nowadays, the
for any
• In
became synonymous with
.
of informations and communications,
the
and
are closely linked to the
development of
with higher and
higher performances but also with lower and lower factory
cost.
CERAMICS PRODUCTS
ABO3 RELATED MATERIALS
• Among these new technical ceramics,
perovskites and
their solid solutions are very attractive for
.
• With the devices miniaturization,
ceramics became
the
for the development of
with artificial intelligence.
• Up to now, the varied
have dominated the market of
microelectronic components. However, the
of
is
a serious
to human
and
.
APPLICATIONS OF ABO3 PEROVSKITES
• Capacitors
• Sensors
• Resonators
• Piezoelectric actuators
• Pyroelectric infrared detectors
• Electro-optical modulators
• Computer and mobile phone memories…
COMPUTER’S MEMORIES
T. Shiosaki, The recent progress in the research and development for ferroelectric memory in Japan (1997)
OBJECTIVES
• To lower both the sintering temperature
(
) and the ferroelectric Curie
temperature (
) of
ceramics using
as additive.
• To reinvestigate the effect of lithium fluoride
on
of
sintered in various conditions.
ceramics
BaTiO3 PROPERTIES
• Phase transitions :
Rhombohedral
193 K
Orthorhombic
278 K
Tetragonal
• Ferroelectric Curie temperature :
• Relaxation frequency :
• Symmetry at room temperature:
393 K
Cubic
BaTiO3 UNIT CELL AT 300 K
EXPERIMENTAL PROCEDURES
•
SAMPLES PREPARATIONS
Barium titanate with various ratio
synthesized by calcination of
and
was previously
at
:
(BT0 0.97)
(BT0 1.00)
(BT0 1.03)
•
Several chemical compositions were then prepared from the varied
and
then wet-ground in ethanol :
•
The powder mixtures were cold-pressed to pellets with an organic
binder. The disks thus obtained were sintered in various conditions.
x BaCO3 + y TiO2
Grinding, Calcination 1100 °C
x wt. % LiF
BaTiO3+CO2
(1-x) % BaTiO3 + x % LiF
Grinding
Sintering (T °C)
METHODS OF INVESTIGATIONS
•
analyzes were carried out at room temperature on
crushed ceramics in the 2 range 10 – 90 °.
observations were performed on
fractured ceramics.
were carried out under vacuum at 1 kHz
between 180 K and 500 K.
Ceramics were investigated by
and
.
were performed and fluorine and lithium losses
were calculated.
RESULTS AND DISCUSSION
DRX spectra of BaTiO3 ceramics sintered with 2 wt. %
LiF at 950 ° C for 2 h
BaO/TiO2
0.97
1.00
1.03
BTO (1.03)
BTO (1.00)
a (Å) c(Å)
3.996 4.032
4.011
4.014
-
• The unit cell remains
BTO (0.97)
•
2  (°)
for
.
The lattice symmetry becomes
for
and
.
Effect of BaO/TiO2 ratio on the permittivity of BaTiO3
ceramics sintered with 2 wt. % LiF at 950 ° C for 2 h
BaO/TiO2  TC(K) ’r
tan
0.97
0.05
303
1200 0.015
1.00
0.145
298
4200 0.008
1.03
0.17
283
5700 0.006
•
•
•
Excess of
inhibits the sintering
and .
Excess of
enhances the
sintering and .
The best dielectric characteristics
are obtained with
Effect of LiF amount on permittivity of BaTiO3 (1.00)
ceramics sintered at 950 ° C for 2 h
LiF
 TC(K)
’r
tan
1 wt. % 0.14
338
3650
0.013
2 wt. % 0.145
298
4200
0.008
3 wt. % 0.145
303
5200
0.007
•
is practically constant.
decreases and increases.
The best dielectric characteristics
are observed with
of .
Effect of LiF amount on permittivity of BaTiO3 (1.03)
ceramics sintered at 950 ° C for 2 h
LiF
 TC(K)
’r
tan
1 wt. % 0.06
313
1500
0.010
2 wt. % 0.17
283
5700
0.006
3 wt. % 0.16
268
6100
0.006
is very low for
•
of
.
decreases and increases.
The best dielectric characteristics
are obtained with
of .
Effect of holding time on permittivity of BaTiO3 (1.00)
ceramics sintered with 2 wt. % LiF at 950 ° C
tsint. (h)  TC(K) ’r
tan
2
0.145
298
4200 0.008
8
0.155
353
3100 0.005
•
increases slightly.
increases and decreases.
The best dielectric characteristics are obtained for
.
Effect of holding time on permittivity of BaTiO3 (1.03)
ceramics sintered with 2 wt. % LiF at 950 ° C
tsint. (h)  TC(K) ’r
tan
2
0.17
283
5700
0.006
8
0.18
293
3900
0.004
•
increases slightly.
increases and decreases.
The best dielectric characteristics are obtained for
.
Effect of sintering temperature on permittivity of
BaTiO3 (1.00) ceramics sintered with 2 wt. % LiF for 2 h
Tsint.(°C) 
TC(K) ’r
tan
750
0.02
373
300
0.015
850
0.14
283
3400
0.008
950
0.145
298
4200
0.008
1100
0.15
288
5700
0.005
•
increases.
decreases and increases.
The best dielectric characteristics
are obtained for
.
Effect of sintering temperature on permittivity of
BaTiO3 (1.03) ceramics sintered with 2 wt. % LiF for 2 h
Tsint. (°C)  TC(K) ’r
tan
750
0.095
393
950
0.012
850
0.165
281
2750
0.008
950
0.17
283
5700
0.006
1100
0.17
263
5250
0.005
•
increases.
decreases and increases
then decreases.
The best dielectric characteristics
are obtained for
.
Temperature dependence of permittivity and losses for BaTiO3
(1.03) ceramic sintered with 2 wt. % LiF at 950 ° C for 2 h in free air
Effect of sintering atmosphere on permittivity of BaTiO3
(1.03) ceramics sintered at 950 °C with 2 wt. % LiF for 2 h
Atmosphere  TC(K) ’r
tan
Free air
0.17
283
5700 0.006
Sealed tube
0.06
383
800
• The
0.017
and the
are obtained when
sintering is performed in
.
Temperature dependence of permittivity of BaTiO3 (1.03)
ceramics sintered with 2 wt. % LiF in various conditions
Sintering
 TC(K) ’r
950°C, 2h, air
0.17
283
5700 0.006
950°C, 2h, air
0.17
+950°C, 48h, ST
263
6750 0.006
950°C, 2h, air
0.17
+1200°C, 2h, ST
248
8650 0.006
• The
tan
are obtained when sintering
is performed at
for
in
then at
in
sealed tube for .
Chemical composition, fluorine and lithium losses of BTO (1.03)
ceramics sintered with 2 wt. % LiF for 2 h at various temperatures
Tsint. (° C) TiO2 (wt. %) BaO (wt.%) F (wt.%) Li (wt.%) F losses (wt.%) Li losses (wt.%)
850
900
950
1100
34.0
34.35
34.50
34.80
65.08
65.08
65.09
65.08
1.15
1.11
0.77
0.47
0.29
0.25
0.18
0.094
21
24
47
68
45
53
66
82
and losses increase with increasing the sintering
temperature. losses are more important than those
of .
DTA and TG thermograms of 98 wt. % BTO (1.03) + 2 wt. % LiF
•
The exothermic peak at
is probably due to
the hydrolysis of
:
DTA
•
TG
The endothermic peak at
around
is ascribed
to and losses.
•
The weight loss reaches
after heating at
for .
280 °C
630 °C
Micrographs of ceramics sintered at 850 or 950 °C
850°C
• The
950°C
increases and the
decreases
with increasing the sintering temperature.
Auger spectra of BaTiO3 (1.03) fractured ceramics sintered
with 2 wt. % LiF at 950 ° C for 2 h
, , , and elements are detected and a
is observed in the grains.
CONCLUSION
•
The effect of
on dielectric properties of
with different ratio
and sintered in various conditions has been reinvestigated.
•
As result, an excess of
inhibits the sintering process and the
permittivity. On the other hand,
excess enhances both the
densification and the dielectric characteristics. The best densification is
obtained with
.
•
The addition of
to
or
lowers simultaneously
the sintering and the ferroelectric Curie temperatures.
or
ceramics display rounded and broad maxima
due to composition gradient in the grains.
•
The ceramics of
could be used for
sintered with
multilayer
at
manufacturing.
for
NORMS OF TYPE II CLASS Z5U CAPACITORS
98 wt. % BTO (1.03) + 2 wt. % LiF, 950 °C, 2 h
+ 22 %
dielectric
Z5U
- 56 %
 ’r (293K) 
•
’r (T) - ’r (293K) / ’r
(293K) =
at
•
’r (T) - ’r (293K) / ’r
(293K) =
at
•
Tan (293K) 
REFERENCES
•
[1] J. M. Haussonne, G. Desgardin, PH. Bajolet, B. Raveau,
JACS, 1983, 66 (11): 801.
•
•
[2] L. Benziada, Thèse de doctorat, 1987.
•
[4] S-F. Wang, T.C.K. Yang, W. Huebner, J.P. Chu, J. Mater. Res.,
2000, 15(2):407.
•
•
[5] L. Zhang, J. Zhai, X. Yao, ferroelectrics, 2009, 384: 153.
•
[7] G. Liu, Y. Jiang, T.W. Button, Ferroelectrics, 2011, 421: 72.
[3] S-F. Wang, K-C. Cheng, Journal of the Chinese Institute of
Engineers, 1999, 22(1): 61.
[6] H. Naghib-zadeh, C. Glitzky, I. Dörfel, T. Rabe, JECS, 2010,
30: 81.