Effect of Bi and Ti additions on the phase formation of Bi4Ti3O12 using fuel-free combustion method.
RAMM & ASMP 2009
Effect of Bi and Ti additions on the phase formation of Bi 4 Ti 3 O 12 using fuel-free
combustion method
A.U. Al-Amani, S. Sreekantan*, M.N. Ahmad Fauzi*
*School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal,
Penang, Malaysia.
E-mail: srimala@eng.usm.my; afauzi@eng.usm.my
Abstract
Bi 4 Ti 3 O 12 was synthesized by fuel-free combustion method using Bi (NO 3 ) 3 .5H 2 O and Ti [OCH (CH 3 ) 2 ] 4
and subsequent calcination. The effect of processing parameters such as Bi addition and Ti addition on the
phase formation of Bi 4 Ti 3 O 12 was investigated. X-Ray Diffraction analysis was used to determine the
formation of Bi 4 Ti 3 O 12 . Pure Bi 4 Ti 3 O 12 powder was successfully formed with Ti addition after calcination
at 800oC for 3 h. The average crystallite sizes produced were 77.9 nm, 63.6 nm and 51.8 nm with mol ratio
of 4:3.1, 4:3.4 and 4:3.6, respectively. The results obtained infer that the relative amount of Ti was
identified as limiting reagent in the combustion reaction and was also considered as key factor to achieve
single-phase Bi 4 Ti 3 O 12 .
Keywords: Bi 4 Ti 3 O 12 ; Bi rich phase; Ti addition
1.0
Introduction
Bismuth titanate, Bi 4 Ti 3 O 12 was first described by Aurivillius in the late 1940s and early 1950s (1). This
composition is also known as bismuth based layered ferroelectric oxide and sometimes as bismuth layer
structure perovskite. The name was given due to its outstanding properties of ferroelectric which is a
special type of dielectric material. The structure of Bi 4 Ti 3 O 12 can be written with a general formula of
(Bi 2 O 2 )2- (A m-1 B m O 3m+1 )2+ where A=Bi, B=Ti and m is equal to 3 (2). It consists of interleaved layers of
bismuth oxide (Bi 2 O 2 )2+ with perovskite units (Bi 2 Ti 2 O 10 2-) and these units are the region where
ferroelectric is generated for its application (1).
The Bi 4 Ti 3 O 12 phase is originally forms in monoclinic at room temperature and upon heating to 600 oC,
this phase is then transforms to tetragonal and afterwards changes to orthorhombic at 750 oC with a=
0.5448 nm, b= 0.5411 nm, c=3.283 nm (1-3). With a wide range of temperature, Bi 4 Ti 3 O 12 is very useful for
various applications such as memory storages, optical displays, piezoelectric converters and pyroelectric
devices (4). As of today, Bi 4 Ti 3 O 12 is being developed for the wireless telecommunication technologies and
it requires very stringent criteria such as high dielectric constant and low dielectric loss (1).
The properties of Bi 4 Ti 3 O 12 are highly dependent on the physical and chemical characteristics such as
stoichiometry, homogeneity, phase purity and particle size distribution (1). To achieve desired properties,
wet chemical method such as hydrothermal, co-precipitation, sol-gel and chemical synthesis were
investigated by several authors (2, 4-7). Shi et al. (8) have prepared the hydrothermal synthesis of Bi 4 Ti 3 O 12
using complex precursors of bismuth nitrate, titanium dioxide, titanium dioxide gel, tetrabutyl titanate
which was then added with mineralizer KOH. Yang et al. (9) have synthesized Bi 4 Ti 3 O 12 nanoparticles by a
low temperature ranging of 180 oC – 230 oC for 4 h - 12 h from bismuth nitrate, titanium chloride and
sodium hydroxide. Pookmanee et al. (10) have reported the Bi 4 Ti 3 O 12 powder was synthesized with longer
heat treatment up to 15 h at 150 oC. However, there has some limitation such as requires complex
preparation during synthesis activity and needs longer heat treatment to induce the reaction.
In present work, the fuel-free combustion method is chosen as an alternative way for the preparation of
ceramics. This method has been developed from self-propagating high-temperature synthesis (SHS)
combined with wet chemical techniques for the synthesizing of metal oxide based ceramic powder (11).
Generally, there are three factors to generate fire which can be described as an uncontrolled combustion.
These factors are oxidizer, temperature and fuel which produce heat, light and ash (12). Fuel-free
combustion method, which does not employ any fuel agents such as citric acid, urea and glycine, makes use
RAMM & ASMP 2009
of low cost precursors resulting in a compositionally homogeneous mixture. It is based on the fact that wet
chemical technique (one part of fuel-free combustion method) can form stable solution with better ion
distribution (13). This method is capable to produce fine powder after combustion takes place (14). Finally,
the experimental set-up is very simple (15). Hence, Bi 4 Ti 3 O 12 has synthesized in our laboratory by fuel-free
combustion method, which was based on aqueous solutions of nitrate salts and titanium (IV) isopropoxide.
2.0
Experiment procedure
The Bi 4 Ti 3 O 12 powders were prepared by fuel-free combustion method using bismuth nitrate, Bi
(NO 3 ) 3 .5H 2 O and titanium isopropoxide, Ti [OCH (CH 3 ) 2 ] 4 as the precursor, 2-Methaoxyethanol as the
solvent and acetylacetone as the chelating agent (as shown in Fig.1). The typical procedure was the
following. Firstly, Bi solution was prepared by adding Bi (NO 3 ) 3 .5H 2 O into 2-Methaoxyethanol and
stirring at 40 oC for 30 min. Secondly, Ti solution was formed by dissolving Ti [OCH (CH 3 ) 2 ] 4 in 2Methaoxyethanol and acetylacetone and stirring for 30 min. Finally, Ti solution was poured into Bi solution
with continuous stirring at 40 oC for 3 h. The temperature setting was then rapidly increased to 130 oC
where combustion took place. The obtained powder was sent for calcination at 800 oC with soaking time of
3 h. The phase structures of the obtained powders were characterized by X-ray diffraction, XRD (Bruker
D8 Advanced). The crystallite size was calculated using Scherrer’s formula at (117) and (111)-reflection on
a-axis and (006)-reflection on c-axis peaks position.
Bi(NO 3 ) 3 .5H 2 O
Ti [OCH (CH 3 ) 2 ] 4
Bi-Ti solution
Evaporation
Viscous solution
Combustion
Foamy powder
Calcination
Calcined powder
Fig. 1: Preparation of Bi 4 Ti 3 O 12 using free-fuel combustion method.
3.0
Result and discussion
3.1
Effect of Bi addition
Fig. 2 shows XRD patterns of the Bi 4 Ti 3 O 12 powders having an excess of Bi at mol ratio of 4.4:3 and
stochiometric composition of 4:3. The Bi 4 Ti 3 O 12 and Bi 12 TiO 20 phases are observed in both powders. The
peaks corresponding to the intermediate phase of Bi 12 TiO 20 appeared at 27.8o, 41.8o, 45.4o and 55.7o. The
Bi 12 TiO 20 diffraction peaks, however, reduced gradually to a minimum content for the powder with the
stochiometric composition. This finding infers that the excess of Bi led to the formation of Bi rich phase
instead of Ti rich phase. This result is in agreement with the one reported by Han and Ko (16) in which they
RAMM & ASMP 2009
reported that Bi rich phase appeared as intermediate phase prior to formation of Bi 4 Ti 3 O 12 phase.
Meanwhile, Bae et al. (15) reported that Bi 4−x La x Ti 3 O 12 phase was fully obtained with the excess of 10mol%
of Bi (NO 3 ) 3 .5H 2 O. However, Stojanovic et al. (3) stated that the excess of 3wt% Bi 2 O 3 did not improve
the milling activity for the formation of Bi 4 Ti 3 O 12 due to small presence of Bi 12 TiO 20 and their starting
materials of Bi 2 O 3 and TiO 2 phases. In order to compare with present study, the presence of Bi 12 TiO 20 at a
calcination temperature of 800oC was not successfully to be eliminated for the powders having Bi excess
and stochiometric composition. Therefore, it implies that the parameter of Bi addition was not resulted on
the formation of single phase of Bi 4 Ti 3 O 12 significantly.
30000
■
25000
Intensity (arb. units)
20000
15000
10000
5000
■ (b)
■
■
■
■ ■ ■♠
■
■■
♠■ ■ ♠
■
■
■
■
■ ■■ ♠ ■
(a)
0
10
20
30
40
50
60
2 Theta (degrees)
Fig. 2: X-ray diffraction patterns of Bi 4 Ti 3 O 12 powders prepared at different Bi ratio and calcined at
800oC for 3h; (a) Bi:Ti=4.4:3 and (b) Bi:Ti=4:3 [■:Bi 4 Ti 3 O 12 / ♠:Bi 12 TiO 20 ].
3.2
Effect of Ti addition
The XRD patterns of the powders having an excess of Ti at different ratio is shown in Fig. 3. The
Bi 12 TiO 20 peaks completely disappeared as the increased of Ti content and all the peaks formed
corresponding to Bi 4 Ti 3 O 12 phase in orthorhombic structure. In this context, Ti is known as limiting
reagent due to its presence into the combustion reaction is in small amount. It is based on the stoichiometry
equation that mol number of Ti is less than Bi-mol number. As a result, Ti needs to be added in relevant
ratio in order to reduce the Bi rich phase. The average crystallite size calculated for the peak position of
(117), (111) and (006) according to the Scherrer equation is shown in Table 1. The crystallite size produced
at ratio of 4:3.1 is 77.9 nm. However, the crystallite size was gradually decreased to 63.6 nm and 51.8 nm
at ratio of 4:3.4 and 4:3.6, respectively. The size obtained is smaller than the size reported by Goh et. al (14)
where at peak position of (117) the Bi 4 Ti 3 O 12 has the largest crystallite size of 97.46 nm. The lattice
constant ‘a’ and ‘c’ are found to be increased as the increased of Ti content. This result indicates that the
ratio of the lattice constant of Bi 4 Ti 3 O 12 , c/a is a function of the Ti content. The ratio of c/a slightly
decreases from 6.032 to 6.010 for 4:3.1 to 4:3.6, respectively. The difference of lattice constant of ‘a’ and
‘c’ for the powder ratio of 4:3.1 is well to be said not so obvious as compared to the lattice constant
recorded from PDF file of 01-089-7500. Thus, the c/a value of the powder is quite close and well accepted
in this work.
RAMM & ASMP 2009
35000
(117) ■
30000
Intensity (arb. units)
25000
15000
■
(111)
20000
■
(006)
■ (d) ■
■ ■ ■
■
■■
■
■
■ ■ ■■
■
■
■
■
(c)
10000
(b)
5000
♠
(a)
♠
0
10
20
30
40
♠
♠
50
60
2Theta (degrees)
Fig. 3: X-ray diffraction patterns of Bi 4 Ti 3 O 12 powders prepared at different Ti ratio and calcined
at 800oC for 3h; (a) Bi:Ti=4.3, (b) Bi:Ti=4.3.1, (c) Bi:Ti=4:3.4 and (d) Bi:Ti=4:3.6 [■:Bi 4 Ti 3 O 12 /
♠:Bi 12 TiO 20 ].
Table 1: Crystallite size, lattice constant (a, c) and ratio c/a
Sample (Bi:Ti)
Ave. crystallite size (nm)
a (nm)
c (nm)
c/a
4.0
4:3.1
77.9
5.4535
32.8972
6.032
4:3.4
63.6
5.4694
32.9520
6.025
4:3.6
51.8
5.5126
33.1299
6.010
01-089-7500
Not available
5.4444
32.8425
6.032
Conclusion
Bi 4 Ti 3 O 12 powder was synthesized using fuel-free combustion method. The studies from different
perceptive on precursor solution which focused on Bi addition and Ti addition led to different phase
formation. The former attempts had resulted the presence of Bi rich phase of Bi 12 TiO 20 while the later
attempt had successfully formed pure single-phase of Bi 4 Ti 3 O 12 with orthorhombic structure after
calcination at 800oC for 3 h.
5.0
Acknowledgements
The authors appreciate technical supports from School of Materials and Mineral Resources Engineering,
USM. This research was supported by Science fund 305/Pbahan/6013357 and USM Fellow-ship.
RAMM & ASMP 2009
6.0
References
(1) Lazarević Z., Stojanović B.D., Varela, J.A., An Approach to Analyzing Synthesis, Structure and
Properties of Bismuth Titanate Ceramics, Science of Sintering, 37, 2005, pp.199-216.
(2) Thongtem, T., Thongtem, S., Characterization of Bi 4 Ti 3 O 12 powder prepared by the citrate and oxalate
coprecipitation processes, Ceramics International, 30, 2004, pp. 1463–1470.
(3) Stojanovic´, B.D., Paiva-Santos, C.O., Cilense, M., Jovalekic´, C., Lazarevic´, Z.Z., Structure study of
Bi 4 Ti 3 O 12 produced via mechanochemically assisted synthesis, Materials Research Bulletin, 43, 2008,
pp. 1743–1753.
(4) Umabala, A.M., Suresh, M., Prasadarao, A.V., Bismuth titanate from coprecipitated stoichiometric
hydroxide precursors, Materials Letters, 44, 2000, pp. 175–180.
(5) Chen, D., Jiao, X., Hydrothermal synthesis and characterization of Bi 4 Ti 3 O 12 powders from different
precursors, Materials Research Bulletin, 36, 2001, pp. 355–363.
(6) Chen, X.Q., Qi, H.Y., Qi, Y.J., Lu, C.J., Ferroelectric and dielectric properties of bismuth neodymium
titanate ceramics prepared using sol–gel derived fine powders, Physics Letters, A 346, 2005, pp. 204–
208.
(7) Pookmanee, P., Chemical synthesis and characterization of lead-free bismuth titanate (Bi 4 Ti 3 O 12 ) from
the oxalate method, Journal of Ceramic Processing Research, Vol. 9, No. 1, 2008, pp. 30-33.
(8) Shi, Y., Cao, C., Feng, S., Hydrothermal synthesis and characterization of Bi 4 Ti 3 O 12 , Materials Letters,
46, 2000, pp. 270–273.
(9) Yang, Q., Li, Y., Yin, Q., Wang, P., Cheng, Y., Bi 4 Ti 3 O 12 nanoparticles prepared by hydrothermal
synthesis, Journal of the European Ceramic Society, 23, 2003, pp. 161–166.
(10) Pookmanee, P., Uriwilast, P., Phanichpant, S., Hydrothermal synthesis of fine bismuth titanate
powders, Ceramics International, 30, 2004, pp. 1913–1915.
(11) Luo, S., Tang, Z., Yao, W., Zhang, Z., Low-temperature combustion synthesis and characterization of
nanosized tetragonal barium titanate powders, Microelectronic Engineering, 66, 2003, pp. 147–152.
(12) Patil, K.C., Hedge, M.S., Rattan, T., Aruna, S.T., Chemistry of Nanocrystalline Oxide Materials
Combustion Synthesis, Properties and Applications, World Scientific Publishing Co. Pte. Ltd.,
Singapore, 2008, pp. 42 (Chapter 3).
(13) Ries, A., Simo˜es, A.Z., Cilense, M., Zaghete, M.A., Varela, J.A., Barium strontium titanate powder
obtained by polymeric precursor method, Materials Characterization, 50, 2003, pp. 217– 221.
(14) Goh, P.Y., Razak, K.A., Sreekantan, S., Structural and morphology studies of praseodymium-doped
bismuth titanate prepared using a wet chemical route, Journal of Alloys and Compounds, xxx, 2008, pp.
xxx–xxx.
(15) Bae, J.C., Kim, S.S., Choi, E.K., Song, T.K., Kim, W.J., Lee, Y.I., Ferroelectric properties of
lanthanum-doped bismuth titanate thin films grown by a sol–gel method, Thin Solid Films, 472, 2005,
pp. 90–95.
(16) Han, K., Ko, T., Synthesis and phase formation of ferroelectric Bi 4 Ti 3 O 12 nanopowder by mechanical
alloying, Journal of Alloys and Compounds, xxx,2008,pp. xxx–xxx.
Effect of Bi and Ti additions on the phase formation of Bi 4 Ti 3 O 12 using fuel-free
combustion method
A.U. Al-Amani, S. Sreekantan*, M.N. Ahmad Fauzi*
*School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal,
Penang, Malaysia.
E-mail: srimala@eng.usm.my; afauzi@eng.usm.my
Abstract
Bi 4 Ti 3 O 12 was synthesized by fuel-free combustion method using Bi (NO 3 ) 3 .5H 2 O and Ti [OCH (CH 3 ) 2 ] 4
and subsequent calcination. The effect of processing parameters such as Bi addition and Ti addition on the
phase formation of Bi 4 Ti 3 O 12 was investigated. X-Ray Diffraction analysis was used to determine the
formation of Bi 4 Ti 3 O 12 . Pure Bi 4 Ti 3 O 12 powder was successfully formed with Ti addition after calcination
at 800oC for 3 h. The average crystallite sizes produced were 77.9 nm, 63.6 nm and 51.8 nm with mol ratio
of 4:3.1, 4:3.4 and 4:3.6, respectively. The results obtained infer that the relative amount of Ti was
identified as limiting reagent in the combustion reaction and was also considered as key factor to achieve
single-phase Bi 4 Ti 3 O 12 .
Keywords: Bi 4 Ti 3 O 12 ; Bi rich phase; Ti addition
1.0
Introduction
Bismuth titanate, Bi 4 Ti 3 O 12 was first described by Aurivillius in the late 1940s and early 1950s (1). This
composition is also known as bismuth based layered ferroelectric oxide and sometimes as bismuth layer
structure perovskite. The name was given due to its outstanding properties of ferroelectric which is a
special type of dielectric material. The structure of Bi 4 Ti 3 O 12 can be written with a general formula of
(Bi 2 O 2 )2- (A m-1 B m O 3m+1 )2+ where A=Bi, B=Ti and m is equal to 3 (2). It consists of interleaved layers of
bismuth oxide (Bi 2 O 2 )2+ with perovskite units (Bi 2 Ti 2 O 10 2-) and these units are the region where
ferroelectric is generated for its application (1).
The Bi 4 Ti 3 O 12 phase is originally forms in monoclinic at room temperature and upon heating to 600 oC,
this phase is then transforms to tetragonal and afterwards changes to orthorhombic at 750 oC with a=
0.5448 nm, b= 0.5411 nm, c=3.283 nm (1-3). With a wide range of temperature, Bi 4 Ti 3 O 12 is very useful for
various applications such as memory storages, optical displays, piezoelectric converters and pyroelectric
devices (4). As of today, Bi 4 Ti 3 O 12 is being developed for the wireless telecommunication technologies and
it requires very stringent criteria such as high dielectric constant and low dielectric loss (1).
The properties of Bi 4 Ti 3 O 12 are highly dependent on the physical and chemical characteristics such as
stoichiometry, homogeneity, phase purity and particle size distribution (1). To achieve desired properties,
wet chemical method such as hydrothermal, co-precipitation, sol-gel and chemical synthesis were
investigated by several authors (2, 4-7). Shi et al. (8) have prepared the hydrothermal synthesis of Bi 4 Ti 3 O 12
using complex precursors of bismuth nitrate, titanium dioxide, titanium dioxide gel, tetrabutyl titanate
which was then added with mineralizer KOH. Yang et al. (9) have synthesized Bi 4 Ti 3 O 12 nanoparticles by a
low temperature ranging of 180 oC – 230 oC for 4 h - 12 h from bismuth nitrate, titanium chloride and
sodium hydroxide. Pookmanee et al. (10) have reported the Bi 4 Ti 3 O 12 powder was synthesized with longer
heat treatment up to 15 h at 150 oC. However, there has some limitation such as requires complex
preparation during synthesis activity and needs longer heat treatment to induce the reaction.
In present work, the fuel-free combustion method is chosen as an alternative way for the preparation of
ceramics. This method has been developed from self-propagating high-temperature synthesis (SHS)
combined with wet chemical techniques for the synthesizing of metal oxide based ceramic powder (11).
Generally, there are three factors to generate fire which can be described as an uncontrolled combustion.
These factors are oxidizer, temperature and fuel which produce heat, light and ash (12). Fuel-free
combustion method, which does not employ any fuel agents such as citric acid, urea and glycine, makes use
RAMM & ASMP 2009
of low cost precursors resulting in a compositionally homogeneous mixture. It is based on the fact that wet
chemical technique (one part of fuel-free combustion method) can form stable solution with better ion
distribution (13). This method is capable to produce fine powder after combustion takes place (14). Finally,
the experimental set-up is very simple (15). Hence, Bi 4 Ti 3 O 12 has synthesized in our laboratory by fuel-free
combustion method, which was based on aqueous solutions of nitrate salts and titanium (IV) isopropoxide.
2.0
Experiment procedure
The Bi 4 Ti 3 O 12 powders were prepared by fuel-free combustion method using bismuth nitrate, Bi
(NO 3 ) 3 .5H 2 O and titanium isopropoxide, Ti [OCH (CH 3 ) 2 ] 4 as the precursor, 2-Methaoxyethanol as the
solvent and acetylacetone as the chelating agent (as shown in Fig.1). The typical procedure was the
following. Firstly, Bi solution was prepared by adding Bi (NO 3 ) 3 .5H 2 O into 2-Methaoxyethanol and
stirring at 40 oC for 30 min. Secondly, Ti solution was formed by dissolving Ti [OCH (CH 3 ) 2 ] 4 in 2Methaoxyethanol and acetylacetone and stirring for 30 min. Finally, Ti solution was poured into Bi solution
with continuous stirring at 40 oC for 3 h. The temperature setting was then rapidly increased to 130 oC
where combustion took place. The obtained powder was sent for calcination at 800 oC with soaking time of
3 h. The phase structures of the obtained powders were characterized by X-ray diffraction, XRD (Bruker
D8 Advanced). The crystallite size was calculated using Scherrer’s formula at (117) and (111)-reflection on
a-axis and (006)-reflection on c-axis peaks position.
Bi(NO 3 ) 3 .5H 2 O
Ti [OCH (CH 3 ) 2 ] 4
Bi-Ti solution
Evaporation
Viscous solution
Combustion
Foamy powder
Calcination
Calcined powder
Fig. 1: Preparation of Bi 4 Ti 3 O 12 using free-fuel combustion method.
3.0
Result and discussion
3.1
Effect of Bi addition
Fig. 2 shows XRD patterns of the Bi 4 Ti 3 O 12 powders having an excess of Bi at mol ratio of 4.4:3 and
stochiometric composition of 4:3. The Bi 4 Ti 3 O 12 and Bi 12 TiO 20 phases are observed in both powders. The
peaks corresponding to the intermediate phase of Bi 12 TiO 20 appeared at 27.8o, 41.8o, 45.4o and 55.7o. The
Bi 12 TiO 20 diffraction peaks, however, reduced gradually to a minimum content for the powder with the
stochiometric composition. This finding infers that the excess of Bi led to the formation of Bi rich phase
instead of Ti rich phase. This result is in agreement with the one reported by Han and Ko (16) in which they
RAMM & ASMP 2009
reported that Bi rich phase appeared as intermediate phase prior to formation of Bi 4 Ti 3 O 12 phase.
Meanwhile, Bae et al. (15) reported that Bi 4−x La x Ti 3 O 12 phase was fully obtained with the excess of 10mol%
of Bi (NO 3 ) 3 .5H 2 O. However, Stojanovic et al. (3) stated that the excess of 3wt% Bi 2 O 3 did not improve
the milling activity for the formation of Bi 4 Ti 3 O 12 due to small presence of Bi 12 TiO 20 and their starting
materials of Bi 2 O 3 and TiO 2 phases. In order to compare with present study, the presence of Bi 12 TiO 20 at a
calcination temperature of 800oC was not successfully to be eliminated for the powders having Bi excess
and stochiometric composition. Therefore, it implies that the parameter of Bi addition was not resulted on
the formation of single phase of Bi 4 Ti 3 O 12 significantly.
30000
■
25000
Intensity (arb. units)
20000
15000
10000
5000
■ (b)
■
■
■
■ ■ ■♠
■
■■
♠■ ■ ♠
■
■
■
■
■ ■■ ♠ ■
(a)
0
10
20
30
40
50
60
2 Theta (degrees)
Fig. 2: X-ray diffraction patterns of Bi 4 Ti 3 O 12 powders prepared at different Bi ratio and calcined at
800oC for 3h; (a) Bi:Ti=4.4:3 and (b) Bi:Ti=4:3 [■:Bi 4 Ti 3 O 12 / ♠:Bi 12 TiO 20 ].
3.2
Effect of Ti addition
The XRD patterns of the powders having an excess of Ti at different ratio is shown in Fig. 3. The
Bi 12 TiO 20 peaks completely disappeared as the increased of Ti content and all the peaks formed
corresponding to Bi 4 Ti 3 O 12 phase in orthorhombic structure. In this context, Ti is known as limiting
reagent due to its presence into the combustion reaction is in small amount. It is based on the stoichiometry
equation that mol number of Ti is less than Bi-mol number. As a result, Ti needs to be added in relevant
ratio in order to reduce the Bi rich phase. The average crystallite size calculated for the peak position of
(117), (111) and (006) according to the Scherrer equation is shown in Table 1. The crystallite size produced
at ratio of 4:3.1 is 77.9 nm. However, the crystallite size was gradually decreased to 63.6 nm and 51.8 nm
at ratio of 4:3.4 and 4:3.6, respectively. The size obtained is smaller than the size reported by Goh et. al (14)
where at peak position of (117) the Bi 4 Ti 3 O 12 has the largest crystallite size of 97.46 nm. The lattice
constant ‘a’ and ‘c’ are found to be increased as the increased of Ti content. This result indicates that the
ratio of the lattice constant of Bi 4 Ti 3 O 12 , c/a is a function of the Ti content. The ratio of c/a slightly
decreases from 6.032 to 6.010 for 4:3.1 to 4:3.6, respectively. The difference of lattice constant of ‘a’ and
‘c’ for the powder ratio of 4:3.1 is well to be said not so obvious as compared to the lattice constant
recorded from PDF file of 01-089-7500. Thus, the c/a value of the powder is quite close and well accepted
in this work.
RAMM & ASMP 2009
35000
(117) ■
30000
Intensity (arb. units)
25000
15000
■
(111)
20000
■
(006)
■ (d) ■
■ ■ ■
■
■■
■
■
■ ■ ■■
■
■
■
■
(c)
10000
(b)
5000
♠
(a)
♠
0
10
20
30
40
♠
♠
50
60
2Theta (degrees)
Fig. 3: X-ray diffraction patterns of Bi 4 Ti 3 O 12 powders prepared at different Ti ratio and calcined
at 800oC for 3h; (a) Bi:Ti=4.3, (b) Bi:Ti=4.3.1, (c) Bi:Ti=4:3.4 and (d) Bi:Ti=4:3.6 [■:Bi 4 Ti 3 O 12 /
♠:Bi 12 TiO 20 ].
Table 1: Crystallite size, lattice constant (a, c) and ratio c/a
Sample (Bi:Ti)
Ave. crystallite size (nm)
a (nm)
c (nm)
c/a
4.0
4:3.1
77.9
5.4535
32.8972
6.032
4:3.4
63.6
5.4694
32.9520
6.025
4:3.6
51.8
5.5126
33.1299
6.010
01-089-7500
Not available
5.4444
32.8425
6.032
Conclusion
Bi 4 Ti 3 O 12 powder was synthesized using fuel-free combustion method. The studies from different
perceptive on precursor solution which focused on Bi addition and Ti addition led to different phase
formation. The former attempts had resulted the presence of Bi rich phase of Bi 12 TiO 20 while the later
attempt had successfully formed pure single-phase of Bi 4 Ti 3 O 12 with orthorhombic structure after
calcination at 800oC for 3 h.
5.0
Acknowledgements
The authors appreciate technical supports from School of Materials and Mineral Resources Engineering,
USM. This research was supported by Science fund 305/Pbahan/6013357 and USM Fellow-ship.
RAMM & ASMP 2009
6.0
References
(1) Lazarević Z., Stojanović B.D., Varela, J.A., An Approach to Analyzing Synthesis, Structure and
Properties of Bismuth Titanate Ceramics, Science of Sintering, 37, 2005, pp.199-216.
(2) Thongtem, T., Thongtem, S., Characterization of Bi 4 Ti 3 O 12 powder prepared by the citrate and oxalate
coprecipitation processes, Ceramics International, 30, 2004, pp. 1463–1470.
(3) Stojanovic´, B.D., Paiva-Santos, C.O., Cilense, M., Jovalekic´, C., Lazarevic´, Z.Z., Structure study of
Bi 4 Ti 3 O 12 produced via mechanochemically assisted synthesis, Materials Research Bulletin, 43, 2008,
pp. 1743–1753.
(4) Umabala, A.M., Suresh, M., Prasadarao, A.V., Bismuth titanate from coprecipitated stoichiometric
hydroxide precursors, Materials Letters, 44, 2000, pp. 175–180.
(5) Chen, D., Jiao, X., Hydrothermal synthesis and characterization of Bi 4 Ti 3 O 12 powders from different
precursors, Materials Research Bulletin, 36, 2001, pp. 355–363.
(6) Chen, X.Q., Qi, H.Y., Qi, Y.J., Lu, C.J., Ferroelectric and dielectric properties of bismuth neodymium
titanate ceramics prepared using sol–gel derived fine powders, Physics Letters, A 346, 2005, pp. 204–
208.
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