Effect of Heat Treatment on the Grain Orientation of Bi3.25Nd0.75Ti3O12 Ceramics.
'{
')':..&.
-str
tx
ISSN: 1823-7010
Malaysian Joumai olNlicroscopy 7 : 132 - 136 (2011)
Effect of Heat Treatment on the Grain Orientation of
Bi3.2sNdo.75Ti3O12 Ceramic
A. UmarAl-Amanir, S. Srimala.r, M.N. Ahmad Fauzir, A.R. Khairunisakl,
S. Tanaka2 and
K. UematsuT
tschool of Materials and Mineral Resou'ce's Engineering'
tJniversiti sains lulalaysia, 14300 Niltong Tebal, Penang, MALAYSIA
2Department of Materials Science and Engineering,
Faculty of Engineering Nagaoka [Jniversity of Technology,
1603-1 KamitorniokQ, Nagaoka, Niigata 940-2188' JAPAN
Neodymium substituted-bismgth titanate, Bir.25Ndo.7iTirOL (BNT075) ceramic was prepared using
soft combustion technique. The dependence ofheat treatment on the grain orientation ofceraniic r'vas
observed. With increasing temperature, the BNT075 ceramic tumed from offc-axis-preferential-oriented
to c-axis-oriented. The result also corresponded to the change from equiaxed structure to plate-1ike
structure, indicating that the grain orientation had a significance influence on grain grorvth,
Keyrvords: c-axis, heat treatment, grain orientation
INTRODUCTIOI\
Over the last decade, much attention has been
paid to lanthanide substituted-bismuth titanate
for their potential applications in nonvolatile
ferroelectric random access memories [1,2].
N eodymium-sdbstituted'uismuth trtanate ts one
of the most popular materials investigated for
this purpose [3]. The outstanding fenoelectricity
such as high remanent polarization (2P,), low
coercive fleld (2E"), good fatigue endurance
and low leakage current are essential in this
application [4]. As reported, the 2P. is highly
dependent on their grain orientation [5]. The
2P. value of the c-axis-oriented BNT films is
-100 pC/cm2 whereas the off c-axis oriented
thin films has the 2P. of 51 pC/cm2 16,71.
Based on this resutt, it would be expected that
the 2P. value of c-axis-oriented BNT thin films
is much higher than that of off c-axis-oriented
films. In the
case to enhance the c-axis-oriented,
several works have been reported over the last
10 years, Bae and co-workers have reported a
fabrication of c-axis-oriented lanthanurn-dopt;
bismuth titanate resulting from the increase i:
annealing temperature [8]. The other way is i.,
use template-grain growth (TGG) method t,-'
orient the textured Nb-doped bismuth titana;t
in. t'a.y,is r.91.,. Ta.nak-a. a-nrl a.nd- ,itJ-wacks,.-s h&l.:
fabricated c-axis-oriented ZtO with a rotati::g
high magnetic field [10]. In this work, we h::;
prepared the grain orientation in c-axis-orieni,;,,
and off-c-axis-oriented BNT075 ceratnic *.ii::
various heat-treatments, whereby the resul::r
were presented in X-ray stnrctural, Lotgeri:i,.
degree of c-oriented and grain morphologies
E
XP ERI1VI E N
Materials and Reagents
The following materials and reagents rvere ttsci
bismuth nitrate penthahydrate (Bi (NO3)r.5FI:i,i.
98%, Sigma Aldrich), neodymium nitr::r
hexahydrate (Nd (NO3)3.6H2O, 99.9olo, Sigr:r',
Aldrich), titanium (IV) isopropoxide iT
'Corresponding author. Tel: + 6{04)-5995255; Fax: + 6(04)-5941011
E-mai1: srimala@eng.usm.my
TAL PRO CE D URE
Eltbct of Heat Treatment on the Crain Orientation of Bi::.Ndo::Ti3O,2 Ceramic
(CH.).11, 97o/o. Merck), acetylacetone
f OCH
(C.HsOr, Merck) and 2-Methaoxyethanol
(
C
H.OCHTCH,OH, Merck).
Stages of heat-treatment
Various heat-treatments were used to investigate
their effect on grain orientation and grain
Preparation of BNT075
The required amounts of Bi (NO,)r.sHrO and Nd
(NO.h.6lir0 were sirnultaneously dissolved in
CH.OCH:CHTOH by stirring at 40oC and 25oC,
respectively, tor 30 min. Separately, Ti IOCH
(CH:):],r r,vas also dissolved in the mixture of
CH.OCHTCH,OH and C5HsO2 with constant
stiring at 25"C for 30 min. Then, Nd solution
rvas slowly added into Bi solution while being
constantiy stirred. It was then followed by Ti
solution rvas added drop-by-drop into Bi-Nd
solution and continuously stirred at 40"C for
alloaher 2 h. Aflow chart is illustrated in Fig. l.
morphoiogies of BNT07-s, The correspondrns
samples HT 1, HTI and HT3 u.ere ob:ained a;er
calcination. pre-sinlerin-e and posl-silterr::.
respectivel),. HT4 ri'as obiained t-,'' a.mosi
same samples as HT3. excepi iha[ pre-s1i:eni1:
was skipped in the processing route. I: car le
simplified as listed in Table 1.
TABLE
1
List of parameter of heat-treatment rvith
heating rate of 5'C/rnin
Sample Heat treatment Temperature Soaking
HTi Calcination 800"C
HT2 Pre-sintering 700"C
HT3 Post-sintering 100'C
HT4 Direct sintering 1100"C
1
Rtu'ruatelia
ls
3h
2h
3h
3h
Characterization
('onrpIcration
X-ray diffraction (XRD, Bruker D8 Advanced)
analysis was carried out to determine the grain
orientation as a result of different heaGtreatment.
Er
rr
prlrirtion
The grain morphologies were displayed by
fleld-ernission scanning electron microscopy
(FE-SEM, Zeiss Supra 55VP PGT/HKL).
The Lotgering degree of grain orientation was
calculated according to the following equation
flll:
u(c-axis)
:
Itool)
Iruon
* Irrrl
Irrrzt
a(otf
c-axts)
'
110u11
+
(l)
(2)
I1l1z1
RESULTS AND DISCUSSIONS
Pr
c-sirrterirrg
XRD Analysis
Pri
"t-sirt
L
Frg 2 shows XRD patterns of the BNT075 with
various heat-treatments. The XRD analysis
teriirg
Sirtrple.flou, chart r;f tlte preparution
B
NT1
7 -5 v'i t h vo r i ous h eo t - I reelnzen ts
d'
Fig.
confirmed that various heat treatments can be
used to form single phase of bismuth-layered
stnlcture. For the sample produced from HTl
and HT2, the most intense peak was dominated
Malaysian Jor.rmal ol lvlicroscopy Vol. 7 201
I
133
A. Umar Al-Arnani, S. Srinrala, M.N. Ahmad Fauzi, A.R. Khairunisak, s. Tanaka and K' l]ematsu
TABLE 2
by (117), suggesting the formation of highly
off-c-axis orientation. On the other hand, the
indexed peak was found to decreasc in the
sample produced from HT3 and HT4. The
increase in intensity of (000 plane is clearly
Degree oforientation for c-axis and
Sample a(c-axis)
seen in XRD pattern, implying that significance
shifted to c-axis-orientation. It is reasonable to
suggest that different axis in grain orientation
is produced with various type of heat treatment'
In addition to that, the degree orientation (u)
a(off c-axis)
HT1
1r.60%
HT2
30.10%
88.40%
69.90%
HT3
71.40%
78.60%
HT4
84.'70%
15.30%
SEM Analysis
of c-axis and off-c-axis was calculated for
respective sample. As calculated, o.-u";. for HTl,
j shows the grain morphologies of thc
BNT075 ceramic with various heat-treatmeuts.
In Frg. 3(a),the HT1 grains mostly consist of
equiaxed-like strucrure with average grain size
of 100 nm to 600 nm, As the porvder is preheated, the HT2 grain size is almost unifornr
Fig.
HT2, HT3 and HT4 was about ll.60/0,30.1oh,
7 l.4Yo and 84.7o/o, respectively, indicating the
increase in c-axis-orientation and decreasing in
off-c-axis-orientation. The calculated value is
shown in Table 2.
due to grain growth of equiaxed-like grain (Flg.
$l
sl
.c
{!
'a
I
sB
i?
t
"H
I
pti?iil
A4: direct sinte ring
ll
o
C
A3: post-sintering
A2: pre-sinlering
I
,l
A1: calcination
I
10
?fl
40
5B
2o
Fig. 2 : X-ray dffi'actian patterns
I l+
offc-axis
o.f
60
{,,)
BNT07 5 at
dffirent
heat tteatment
Malaysian Joumal of Microscopy Vol. 7 201 I
Eltcct ol Hcat Treatment on thc Grain Orientation of Bi,,,Nd, rr1i.Or: Ccramic
-116l). This particular grain growth occurs very
ertensive during post-sintering resulted in HT3
plate-like stmctr.rre (Fig. 3(c)). The platey grain
rs more unifonn with average grain size of2 pm
to 8 prn, The laryest HT4 plate-like structure
is clearly seen resuiting from direct sintering as
shor,vn in FiS 3(cl). The morphoiogy results are
consistcnt rvith the results of XRD and degree
of orientation as reported earlier.
Similar observation was found in the sample
produced from HTI and HT2, whereby the off-caxis became a dominant orientation. However, it
did not occur in the sample produced from HT3
CONCLUSION
ACKNOWLEDGMENT
In summary, the grain orientation of BNT075
The authors appreciate the technical support
cerarnic is highly dependent on heat treatment.
from School ofMaterials and Mineral Resources
and
HT4. The increase in c-axis-orientation
was also confirmed by degree orientation. The
change in grain orientation r,vas clearly seen
in grain morphology, whereby highly-c-axisorientation corresponds to plate-like structure.
I
Istr"W
I
tith vorious heot-teottilents. (a) HTl,
(h) IIT2, (c) H7'3 und (d) HT4
Fig. 3: Grain morphologies of'BNT075
Malaysian Journal of ivlicroscopy Vol. 7 201
I
Tanaka and K. Uematstt
A. UmarAl-Amani, S. Srimala, M.N' Ahmad Fauzi, A.R. Khairunisak, S.
Engineering, Universiti Sains Malaysia' This
research was supported by the E-science Fund
305/Pbahan/ 6013357, USM-RU grant 1 001/
Pbahanl80420 1 8 and
8
1
[5]
Uong, C., Jeong, S.S., HyLrn'
M.l. (2003)' J' Appl'
Phys.93 (8) 4769.
[6]
Chon, U., Jang, H.M., Kirn, M'G', Chang' C'H'
(2002). Phys. Rev. Lett. (89) 087601'
[7]
Yang, B.,Zhang, D.M., Zhou, 8., Huang, L H',
Zheng, C.D., Wu, Y.Y. Guo, D'Y., Yu, J' (2008)'
J. Cryst Grov'th (3 10) 45 I 1 '
1069.
REFERENCES
[1]
Park, B.H., Kang, B.S., Bu, S.D', Noh, T.W., Lee,
J., Jo, W. (1999). Nahrre (401) 682'
[8]
Bae, J.C.,
[2]
Giridharan, N.V., Subramanian, M', Jayavel, R.
(2006). Appl. Phys. A (83) 123.
[9]
[3]
Chen, X.Q., Qi, H.Y., Qi, Y.J., Lu,
Phys. Lett. A (346) 204.
Hong, S.H., Susan, T.M., Gary,
Am. Ceratn.,loc.83 (1) 1i3.
[4] Noh, T.W, Kang, B.S.,
C'i'
(2005).
Seo, S., So, Y.W., Park'
8.H., Bu, S.D.. Yoon, J.G. (2002) Ferroelectrics'
267 (1) r21.
136
Kim, S.S., Choi, E.K., Song, T'K., Kim,
WJ., Lee, Y.I. (2005). Thin Solid Filns (4'12)90
L'M'
(2000)..r.
l10l Satoshi, T., Atsushi, M., Zenji' K., Keizo, U
(2009).J. Eur. Cerarn. Soc. (29) 955.
tl1l Ni,2., Tadashi,
S. (2007).
Malaysian Journal of Microscopy Vol. 7 201I
Mat' Lett, (61) 2935.
')':..&.
-str
tx
ISSN: 1823-7010
Malaysian Joumai olNlicroscopy 7 : 132 - 136 (2011)
Effect of Heat Treatment on the Grain Orientation of
Bi3.2sNdo.75Ti3O12 Ceramic
A. UmarAl-Amanir, S. Srimala.r, M.N. Ahmad Fauzir, A.R. Khairunisakl,
S. Tanaka2 and
K. UematsuT
tschool of Materials and Mineral Resou'ce's Engineering'
tJniversiti sains lulalaysia, 14300 Niltong Tebal, Penang, MALAYSIA
2Department of Materials Science and Engineering,
Faculty of Engineering Nagaoka [Jniversity of Technology,
1603-1 KamitorniokQ, Nagaoka, Niigata 940-2188' JAPAN
Neodymium substituted-bismgth titanate, Bir.25Ndo.7iTirOL (BNT075) ceramic was prepared using
soft combustion technique. The dependence ofheat treatment on the grain orientation ofceraniic r'vas
observed. With increasing temperature, the BNT075 ceramic tumed from offc-axis-preferential-oriented
to c-axis-oriented. The result also corresponded to the change from equiaxed structure to plate-1ike
structure, indicating that the grain orientation had a significance influence on grain grorvth,
Keyrvords: c-axis, heat treatment, grain orientation
INTRODUCTIOI\
Over the last decade, much attention has been
paid to lanthanide substituted-bismuth titanate
for their potential applications in nonvolatile
ferroelectric random access memories [1,2].
N eodymium-sdbstituted'uismuth trtanate ts one
of the most popular materials investigated for
this purpose [3]. The outstanding fenoelectricity
such as high remanent polarization (2P,), low
coercive fleld (2E"), good fatigue endurance
and low leakage current are essential in this
application [4]. As reported, the 2P. is highly
dependent on their grain orientation [5]. The
2P. value of the c-axis-oriented BNT films is
-100 pC/cm2 whereas the off c-axis oriented
thin films has the 2P. of 51 pC/cm2 16,71.
Based on this resutt, it would be expected that
the 2P. value of c-axis-oriented BNT thin films
is much higher than that of off c-axis-oriented
films. In the
case to enhance the c-axis-oriented,
several works have been reported over the last
10 years, Bae and co-workers have reported a
fabrication of c-axis-oriented lanthanurn-dopt;
bismuth titanate resulting from the increase i:
annealing temperature [8]. The other way is i.,
use template-grain growth (TGG) method t,-'
orient the textured Nb-doped bismuth titana;t
in. t'a.y,is r.91.,. Ta.nak-a. a-nrl a.nd- ,itJ-wacks,.-s h&l.:
fabricated c-axis-oriented ZtO with a rotati::g
high magnetic field [10]. In this work, we h::;
prepared the grain orientation in c-axis-orieni,;,,
and off-c-axis-oriented BNT075 ceratnic *.ii::
various heat-treatments, whereby the resul::r
were presented in X-ray stnrctural, Lotgeri:i,.
degree of c-oriented and grain morphologies
E
XP ERI1VI E N
Materials and Reagents
The following materials and reagents rvere ttsci
bismuth nitrate penthahydrate (Bi (NO3)r.5FI:i,i.
98%, Sigma Aldrich), neodymium nitr::r
hexahydrate (Nd (NO3)3.6H2O, 99.9olo, Sigr:r',
Aldrich), titanium (IV) isopropoxide iT
'Corresponding author. Tel: + 6{04)-5995255; Fax: + 6(04)-5941011
E-mai1: srimala@eng.usm.my
TAL PRO CE D URE
Eltbct of Heat Treatment on the Crain Orientation of Bi::.Ndo::Ti3O,2 Ceramic
(CH.).11, 97o/o. Merck), acetylacetone
f OCH
(C.HsOr, Merck) and 2-Methaoxyethanol
(
C
H.OCHTCH,OH, Merck).
Stages of heat-treatment
Various heat-treatments were used to investigate
their effect on grain orientation and grain
Preparation of BNT075
The required amounts of Bi (NO,)r.sHrO and Nd
(NO.h.6lir0 were sirnultaneously dissolved in
CH.OCH:CHTOH by stirring at 40oC and 25oC,
respectively, tor 30 min. Separately, Ti IOCH
(CH:):],r r,vas also dissolved in the mixture of
CH.OCHTCH,OH and C5HsO2 with constant
stiring at 25"C for 30 min. Then, Nd solution
rvas slowly added into Bi solution while being
constantiy stirred. It was then followed by Ti
solution rvas added drop-by-drop into Bi-Nd
solution and continuously stirred at 40"C for
alloaher 2 h. Aflow chart is illustrated in Fig. l.
morphoiogies of BNT07-s, The correspondrns
samples HT 1, HTI and HT3 u.ere ob:ained a;er
calcination. pre-sinlerin-e and posl-silterr::.
respectivel),. HT4 ri'as obiained t-,'' a.mosi
same samples as HT3. excepi iha[ pre-s1i:eni1:
was skipped in the processing route. I: car le
simplified as listed in Table 1.
TABLE
1
List of parameter of heat-treatment rvith
heating rate of 5'C/rnin
Sample Heat treatment Temperature Soaking
HTi Calcination 800"C
HT2 Pre-sintering 700"C
HT3 Post-sintering 100'C
HT4 Direct sintering 1100"C
1
Rtu'ruatelia
ls
3h
2h
3h
3h
Characterization
('onrpIcration
X-ray diffraction (XRD, Bruker D8 Advanced)
analysis was carried out to determine the grain
orientation as a result of different heaGtreatment.
Er
rr
prlrirtion
The grain morphologies were displayed by
fleld-ernission scanning electron microscopy
(FE-SEM, Zeiss Supra 55VP PGT/HKL).
The Lotgering degree of grain orientation was
calculated according to the following equation
flll:
u(c-axis)
:
Itool)
Iruon
* Irrrl
Irrrzt
a(otf
c-axts)
'
110u11
+
(l)
(2)
I1l1z1
RESULTS AND DISCUSSIONS
Pr
c-sirrterirrg
XRD Analysis
Pri
"t-sirt
L
Frg 2 shows XRD patterns of the BNT075 with
various heat-treatments. The XRD analysis
teriirg
Sirtrple.flou, chart r;f tlte preparution
B
NT1
7 -5 v'i t h vo r i ous h eo t - I reelnzen ts
d'
Fig.
confirmed that various heat treatments can be
used to form single phase of bismuth-layered
stnlcture. For the sample produced from HTl
and HT2, the most intense peak was dominated
Malaysian Jor.rmal ol lvlicroscopy Vol. 7 201
I
133
A. Umar Al-Arnani, S. Srinrala, M.N. Ahmad Fauzi, A.R. Khairunisak, s. Tanaka and K' l]ematsu
TABLE 2
by (117), suggesting the formation of highly
off-c-axis orientation. On the other hand, the
indexed peak was found to decreasc in the
sample produced from HT3 and HT4. The
increase in intensity of (000 plane is clearly
Degree oforientation for c-axis and
Sample a(c-axis)
seen in XRD pattern, implying that significance
shifted to c-axis-orientation. It is reasonable to
suggest that different axis in grain orientation
is produced with various type of heat treatment'
In addition to that, the degree orientation (u)
a(off c-axis)
HT1
1r.60%
HT2
30.10%
88.40%
69.90%
HT3
71.40%
78.60%
HT4
84.'70%
15.30%
SEM Analysis
of c-axis and off-c-axis was calculated for
respective sample. As calculated, o.-u";. for HTl,
j shows the grain morphologies of thc
BNT075 ceramic with various heat-treatmeuts.
In Frg. 3(a),the HT1 grains mostly consist of
equiaxed-like strucrure with average grain size
of 100 nm to 600 nm, As the porvder is preheated, the HT2 grain size is almost unifornr
Fig.
HT2, HT3 and HT4 was about ll.60/0,30.1oh,
7 l.4Yo and 84.7o/o, respectively, indicating the
increase in c-axis-orientation and decreasing in
off-c-axis-orientation. The calculated value is
shown in Table 2.
due to grain growth of equiaxed-like grain (Flg.
$l
sl
.c
{!
'a
I
sB
i?
t
"H
I
pti?iil
A4: direct sinte ring
ll
o
C
A3: post-sintering
A2: pre-sinlering
I
,l
A1: calcination
I
10
?fl
40
5B
2o
Fig. 2 : X-ray dffi'actian patterns
I l+
offc-axis
o.f
60
{,,)
BNT07 5 at
dffirent
heat tteatment
Malaysian Joumal of Microscopy Vol. 7 201 I
Eltcct ol Hcat Treatment on thc Grain Orientation of Bi,,,Nd, rr1i.Or: Ccramic
-116l). This particular grain growth occurs very
ertensive during post-sintering resulted in HT3
plate-like stmctr.rre (Fig. 3(c)). The platey grain
rs more unifonn with average grain size of2 pm
to 8 prn, The laryest HT4 plate-like structure
is clearly seen resuiting from direct sintering as
shor,vn in FiS 3(cl). The morphoiogy results are
consistcnt rvith the results of XRD and degree
of orientation as reported earlier.
Similar observation was found in the sample
produced from HTI and HT2, whereby the off-caxis became a dominant orientation. However, it
did not occur in the sample produced from HT3
CONCLUSION
ACKNOWLEDGMENT
In summary, the grain orientation of BNT075
The authors appreciate the technical support
cerarnic is highly dependent on heat treatment.
from School ofMaterials and Mineral Resources
and
HT4. The increase in c-axis-orientation
was also confirmed by degree orientation. The
change in grain orientation r,vas clearly seen
in grain morphology, whereby highly-c-axisorientation corresponds to plate-like structure.
I
Istr"W
I
tith vorious heot-teottilents. (a) HTl,
(h) IIT2, (c) H7'3 und (d) HT4
Fig. 3: Grain morphologies of'BNT075
Malaysian Journal of ivlicroscopy Vol. 7 201
I
Tanaka and K. Uematstt
A. UmarAl-Amani, S. Srimala, M.N' Ahmad Fauzi, A.R. Khairunisak, S.
Engineering, Universiti Sains Malaysia' This
research was supported by the E-science Fund
305/Pbahan/ 6013357, USM-RU grant 1 001/
Pbahanl80420 1 8 and
8
1
[5]
Uong, C., Jeong, S.S., HyLrn'
M.l. (2003)' J' Appl'
Phys.93 (8) 4769.
[6]
Chon, U., Jang, H.M., Kirn, M'G', Chang' C'H'
(2002). Phys. Rev. Lett. (89) 087601'
[7]
Yang, B.,Zhang, D.M., Zhou, 8., Huang, L H',
Zheng, C.D., Wu, Y.Y. Guo, D'Y., Yu, J' (2008)'
J. Cryst Grov'th (3 10) 45 I 1 '
1069.
REFERENCES
[1]
Park, B.H., Kang, B.S., Bu, S.D', Noh, T.W., Lee,
J., Jo, W. (1999). Nahrre (401) 682'
[8]
Bae, J.C.,
[2]
Giridharan, N.V., Subramanian, M', Jayavel, R.
(2006). Appl. Phys. A (83) 123.
[9]
[3]
Chen, X.Q., Qi, H.Y., Qi, Y.J., Lu,
Phys. Lett. A (346) 204.
Hong, S.H., Susan, T.M., Gary,
Am. Ceratn.,loc.83 (1) 1i3.
[4] Noh, T.W, Kang, B.S.,
C'i'
(2005).
Seo, S., So, Y.W., Park'
8.H., Bu, S.D.. Yoon, J.G. (2002) Ferroelectrics'
267 (1) r21.
136
Kim, S.S., Choi, E.K., Song, T'K., Kim,
WJ., Lee, Y.I. (2005). Thin Solid Filns (4'12)90
L'M'
(2000)..r.
l10l Satoshi, T., Atsushi, M., Zenji' K., Keizo, U
(2009).J. Eur. Cerarn. Soc. (29) 955.
tl1l Ni,2., Tadashi,
S. (2007).
Malaysian Journal of Microscopy Vol. 7 201I
Mat' Lett, (61) 2935.