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Research ArticleThe Novel Formation of Barium Titanate Nanodendrites

Chien-Jung Huang1 Kan-Lin Chen2 Pin-Hsiang Chiu3 Po-Wen Sze4

and Yeong-Her Wang35

1 Department of Applied Physics National University of Kaohsiung Nanzih Kaohsiung Taiwan2Department of Electronic Engineering Fortune Institute of Technology Kaohsiung Taiwan3 Institute of Electro-Optical Science and Engineering Institute of Microelectronics National Cheng-Kung UniversityTainan Taiwan

4Department of Electro-Optical Science and Engineering Kao Yuan University Kaohsiung Taiwan5Department of Electrical Engineering Institute of Microelectronics National Cheng-Kung University Tainan Taiwan

Correspondence should be addressed to Chien-Jung Huang chiennukedutw and Kan-Lin Chen klchenfotechedutw

Received 15 March 2014 Accepted 26 March 2014 Published 30 April 2014

Academic Editor Fu-Ken Liu

Copyright copy 2014 Chien-Jung Huang et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The barium titanate (BaTiO3) nanoparticles with novel dendrite-like structures have been successfully fabricated via a simple

coprecipitation method the so-called BaTiO3nanodendrites (BTNDs) This method was remarkable fast simple and scalable

The growth solution is prepared by barium chloride (BaCl2) titanium tetrachloride (TiCl

4) and oxalic acid The shape and size of

BaTiO3depend on the amount of added BaCl

2solvent To investigate the influence of amount of BaCl

2on BTNDs the amount of

BaCl2was varied in the range from 3 to 6mLThe role of BaCl

2is found to have remarkable influence on themorphology crystallite

size and formation of dendrite-like structures The thickness and length of the central stem of BTND were sim300 nm and sim20 120583mrespectively The branchings were found to occur at irregular intervals along the main stem Besides the formation mechanism ofBTND is proposed and discussed

1 Introduction

Over the past few years the unique ferroelectric piezo-electric and thermoelectric properties of barium titanate(BaTiO

3) nanoparticles have become increasingly important

in the electronic ceramics industryTheBaTiO3nanoparticles

have been extensively applied in various fields such as mul-tilayer ceramic capacitors (MLCCs) integral capacitors inprinted circuit boards (PCB) dynamic random access mem-ories (DRAM) resistors with positive temperature coefficientof resistivity (PTCR) temperature-humidity-gas sensorselectrooptic devices piezoelectric transducers actuators andthermistors [1ndash9] Among these applications performanceand characteristics are strongly influenced by size shapecompositionmorphology spatial ordering and impurities ofthe BaTiO

3nanoparticles Thus effectively controlling their

shape and size is of high importance and is a challengingtask for researchers and the industry In this work we have

developed BaTiO3with novel dendrite-like structures Very

recently nanoparticles with dendrite-like structures havereceivedmuch attention because of their potential applicationin device [10 11] However finely controlling themorphologyof the BaTiO

3nanoparticles is extremely dependent on

preparation method and synthesis procedureTraditionally the BaTiO

3particle is prepared by the solid-

state reaction method through heating BaCO3and TiO

2at

high temperature as 1200∘C [12 13] The disadvantage of thismethod is that high calcinations temperature may stronglycause aggregation between the particles and it takes a longtime to produce submicrometer particles (1sim2 120583m) Up tonow various new preparation methods have been developedand reported in fabricating BaTiO

3nanoparticles with high

quality well-controlled shape and small size such as thesol-gel method [14 15] the hydrothermal method [16 17]the Pechini processing using a citric or oxalate complexas the precursor [18 19] the ball-milling method [20 21]

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2014 Article ID 718918 6 pageshttpdxdoiorg1011552014718918

2 Journal of Nanomaterials

the polymeric precursor method [22] the soft chemicalprocess [23] the glycolthermal method [24] and the copre-cipitation method [25] Among these the coprecipitationmethod is superior to othermethods in terms of the followingcharacteristics high growth rate modest equipment lowprocessing temperature ease of controlling the yield lowcost large amount synthesized and high quality [26]

In the coprecipitationmethod the preparation of BaTiO3

nanoparticles through the coprecipitation of barium and tita-nium hydroxides from aqueous solutions has been reportedsince the early Flaschen research work [27] Synthesis ofBaTiO

3nanoparticles as the decomposition product of bar-

ium titanyl oxalate or barium titanyl citrate is a multistageprocess depending on the gaseous medium the dispersionof the starting reagents and intermediate phase (the degree ofbranching of the interphase surface) the regime in which thereaction occurs (kinetic or diffusion) the growth tempera-ture and the heating rate [28ndash32] Although these previousstudies succeeded in fabricating BaTiO

3nanoparticles the

procedure is quite complicated Furthermore these proce-dures also require special conditions such as judicious choiceof the stabilizer heat treatment and time durationThereforeit will be a significant challenge to simplify the procedure forthe fabrication of BaTiO

3nanoparticles

In our laboratory we developed a simple procedureby slightly modifying the multistage process so it couldbe applied to fabricate BaTiO

3nanoparticles with well-

controlled size In this simple procedure appropriate amountof stock solution of titanium tetrachloride (TiCl

4) barium

chloride (BaCl2) and oxalic acid was added in deionized

water to form growth solution The BaTiO3nanoparticle

was formed by coprecipitation of both barium and titaniumprecursor During the coprecipitation process titanium actedas the seed in the growth solution so that the barium couldnucleate and precipitate onto the surfaces of titanium viathe heterogeneous nucleation process More importantly itis found that the amount of added BaCl

2can be critical for

shape and size of BaTiO3nanoparticles

In this study we first reported the fabrication of BaTiO3

nanoparticles with novel dendrite-like structures through thecoprecipitation method the so-called BaTiO

3nanodendrites

(BTNDs) It can be observed that the various amounts ofadded BaCl

2during nucleation and growth process caused

the alteration of the BaTiO3nanoparticles shape forming

the branch-like structures Until now to our knowledgethere are no reports yet on the synthesis of the BTNDsby coprecipitation method A good understanding of themicrostructure properties is a very important issue for thepotential application of the BTNDs Thus a detailed modelfor the newly observed novel BTNDs is also proposed toexplain their possible formation mechanism

2 Experimental Details

Barium chloride (BaCl2sdot2H2O 99) and oxalic acid

(C2H2O4sdot2H2O 99) were obtained from Riedel-deHa en

(Sigma-Aldrich USA) Titanium tetrachloride solution

(TiCl4 99 01M) was purchased from Fluka (Sigma-

Aldrich USA) All chemicals and materials were usedwithout further purification The distilled water usedthroughout the experiments was purified by a Milli-Qsystem (Millipore resistivity 182MΩ cm) The BTNDs werefabricated by first dissolving BaCl

2in distilled water at 50ndash

70∘C Separately oxalic acid was dissolved in distilled waterat 65∘C in an ultrasonic tank with titanium tetrachlorideslowly added The two solutions were mixed in an ultrasonicbath at 65∘C Nanometer-sized BaTiO

3particles were formed

at this stage Finally the growth time was 20minThe size and shape of the BTNDsweremeasured and ana-

lyzed by transmission electronmicroscopy (TEM JEOL JEM-1230) at an accelerating voltage of 80 kV The microstructureof the BTNDs was observed by high-resolution transmissionelectron microscopy (HRTEM Philips Tecnai G2 F20) withan accelerating voltage of 200 kVThe HRTEMwas equippedwith selected area electron diffraction (SAED) and an energy-dispersive X-ray (EDX) spectrometric element analyzer Thesamples for TEM SAED and EDX were prepared by dropcoating onto a standard 200-mesh 3mm carbon-coatedcopper grid (Agar Scientific UK)

3 Results and Discussion

Figures 1(a)ndash1(d) show the TEM images of BaTiO3nanoparti-

cles obtained by adding 3 4 5 and 6mL of BaCl2The results

clearly show that the shape of the BaTiO3nanoparticles can be

changed by altering the amount of BaCl2 When the amount

of BaCl2was 3mL the BaTiO

3nanoparticles with large

quantities were almost spherical in shape and were small insize as shown in Figure 1(a)The inset of Figure 1(a) shows theTEM image of BaTiO

3nanoparticles at higher magnification

indicating that the particle size is about 20 nm When theamount of BaCl

2was increased from 4 to 5mL the shape

of BaTiO3nanoparticles began to change from spherical to

dendrite-like as shown in Figures 1(b) and 1(c) When theamount of BaCl

2was 6mL the BaTiO

3nanoparticles were

almost dendrite-like in shape as shown in Figure 1(d) Evenafter sonication for TEM sample preparation the branches ofthe dendrites were intact indicating strong bonding betweenthe grains Thus there is not any isolated spherical BaTiO

3

particles in TEM image However the role of BaCl2may

be to act as shape-modifier to change BaTiO3nanoparticlesrsquo

shape from spherical to dendrite-like structure when theBaCl2with high amountwas added to growth solution during

coprecipitation process Besides these results also show thatthe size of BaTiO

3nanoparticles increased as the amount of

BaCl2increased as revealed TEM analysis (Figure 1)

Figure 2 shows the low-magnification TEM images ofsingle BTND prepared with 6mL of BaCl

2 As can be seen

in Figure 2(a) the BTND described as dendritic structureshas a large area of several square micrometers The thicknessof the central stem of BTND was sim300 nm Along thecentral stem (with length of sim20120583m) branching was seenfor every sim300 nm The lengths of the side branches werefound to be different for the same BTND Also the anglebetween the main stem and the branch was not constant

Journal of Nanomaterials 3

Table 1 Preparation of BaTiO3 particles using oxalate process

Step 1 synthesis of mixed oxalateTiCl4 + H2O 997888rarr TiOCl2 + 2HCl (1)BaCl2 + TiOCl2 + 2H2C2O4 + 4H2O 997888rarr BaTiO(C2O4)2sdot4H2O + 4HCl (2)

Step 2 thermal decompositionBaTiO(C2O4)2sdot4H2O 997888rarr BaTiO(C2O4)2 + 4H2O (3)BaTiO(C2O4)2 997888rarr 05BaTi2O5 + 05BaCO3 + 2CO + 15CO2 (4)05BaTi2O5 + 05BaCO3 997888rarr BaTiO3 darr + 05CO2 (5)

(a) (b)

(c) (d)

Figure 1 Transmission electronmicroscopy (TEM) images of the BaTiO3nanoparticles prepared by (a) 3 (b) 4 (c) 5 and (d) 6mL of barium

chloride

for all the cases as shown in Figure 2(b) The aggregatedcrystallites may form a BTND by oriented attachment of thecrystallites The inset of Figure 2(b) shows the SAED patternof the individual grain from the BTND The characteristicring in the polycrystalline diffraction pattern confirmed that

the BTNDs are polycrystalline structures Figure 2(c) showshigh-magnification TEM image of stem of single BTNDwhich clearly shows that the dendrite-like structure consistedof eleven large BaTiO

3particles and many small BaTiO

3

compounds between the particles Figure 2(d) schematically


(a) (b)

(c)

1 1

2 2

3 3

4 4

5 5

6 6

7 7

8 8

9 9

10 10

11 11

Growth

Large particle

Small compounds

Formation of dendrite-like structures

(d)

Figure 2 TEM images of the BTND obtained by the oxalate coprecipitation method (a) low-magnification image (b) high-magnificationimage and SAED pattern (c) the part of BTND at the stem and (d) schematic illustration of formation of BTND

shows the formation mechanism of BTNDs The BTNDswere formed by aggregation of many small BaTiO

3com-

pounds between the large BaTiO3particles during the growth

process indicating that small BaTiO3compounds linked

the large BaTiO3particles to form the dendrite-like shape

However the present study is to show that the amountof BaCl

2is a key parameter in the formation of BaTiO

3

nanoparticles with various sizes and shapesThe BaTiO

3nanoparticles produced using the coprecipi-

tation method were analyzed by using EDX for studying thecomposition of BaTiO

3nanoparticles as shown in Figure 3

The elements detected should be carbon oxygen titanium(Ti) and barium (Ba) in the present method No otherelements were detected indicating that the sample is purelyBaTiO

3 The peaks of copper (Cu) and carbon in this chart

correspond to the Cu grid coated with a thin carbon filmas a carrier of the BaTiO

3nanoparticles during the test The

above findings support the hypothesis that the formationof BTNDs process is as follows The relationship betweenthe formation of BTNDs and the amount of BaCl

2can be

easily explained through the chemical formation of BaTiO3

particles during oxalate process [33] as shown in Table 1

Journal of Nanomaterials 5C

ount

s

Energy (keV)

400

200

0

0 5 10 15

C

O

CuCu

CuCuCu

Ba

Ba Ba Ba

TiTi

Ti

Figure 3 TEM image of single BTND and corresponding EDXspectra

The precipitation of monodisperse BaTiO3particles is gen-

erally formed with the synthesis of mixed oxalate (Step 1)and the thermal decomposition (Step 2) According to (1)of Step 1 Ti (IV) hydroxo complexes or Ti (IV) polyanionsare produced by hydrolysis and condensation reactionsAccording to (2) of Step 1 starting materials TiCl

4and BaCl

2

are reacted with water and oxalic acid (H2C2O4) to precipi-

tate a double oxalate (BaTiO(C2O4)2sdot4H2O) precursor This

precursor was obtained by the reaction which proceeds intwo steps (i) initial rapid formation of a Ti-rich gel phaseand (ii) slower reaction between the gel phase and the Ba2+left in solution According to Step 2 this precursor duringgrowth process then results in formation of small BaTiO

3

compounds (at atomic- or molecular-level compositionalhomogeneity) through thermal decomposition Finally theaggregation and the agglomeration of many small BaTiO

3

compounds lead to the formation of crystalline BaTiO3

particle and awhite BaTiO3particle precipitate can be readily

observed According to (2) the amount of double oxalateprecursor is increased as the amount of BaCl

2increases

when the TiCl4is enough amounts In other words the

amount of small BaTiO3compounds is increased with the

increase in amount of double oxalate precursor as shownin Step 2 of Table 1 Thus the aggregation of small BaTiO

3

compounds is enhanced when the amount of small BaTiO3

compounds increases resulting in the growth of BaTiO3

nanoparticles being enhanced and causing the size of theBaTiO

3nanoparticles to be increased However the size of

BaTiO3nanoparticles is directly proportioned to amount of

BaCl2 with the results being consistent with TEM analysis of

Figure 1In this study we propose that the addition of BaCl

2

causes the possible mechanism of BTNDs formation It isfound that a high amount of BaCl

2led to formation of large

BaTiO3particles and small BaTiO

3compounds during the

coprecipitation growth that caused particle agglomeration toform BTNDs in the growth solution as shown in Figure 2The small BaTiO

3compounds aggregated onto the surface of

the large BaTiO3particles by the van der Waals attractions

forces during growth process It is considered to comprisemainly two processes (i) the formation of small BaTiO

3

compounds at the growth process and (ii) the subsequent

anisotropic coalescence of these small BaTiO3compounds

leading to the BTNDs formation that is to say these smallBaTiO

3compounds with an unstable state show a tendency

to undergo fusion into dendrite-like structures Hence theamount of BaCl

2definitely has a critical role in the formation

of the BTNDs However formation mechanism for BTNDsusing the coprecipitation method via BaCl

2addition is still

under investigation

4 Conclusions

In summary this study prepares polycrystalline BTNDs by asimple coprecipitation method It has been observed that theamount of BaCl

2plays an important role in the formation

of BTNDs Change in the amount of BaCl2from 3 to

6mL strongly affected the shape of particles from sphere todendrite-like shape The formation of BTNDs was inducedby aggregation of many small BaTiO

3compounds between

the several large BaTiO3particles during growth causing the

small BaTiO3compounds to link to the large BaTiO

3particles

forming dendrite-like structures Further measurements arenow necessary to get a better understanding of these BTNDsThis preparation of BTNDs is proven to be a simple andeffective synthesis method

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was partially supported by the National ScienceCouncil of Taiwan (NSCT) under Contract no NSC 102-2221-E-390-019-MY2 The authors gratefully acknowledgethe Southern Taiwan University of Technology (Taiwan) forthe TEMmeasurement

References

[1] U van Stevendaal K Buse S Kamper H Hesse and E KratzigldquoLight-induced charge transport processes in photorefractivebarium titanate doped with rhodium and ironrdquo Applied PhysicsB Lasers and Optics vol 63 no 4 pp 315ndash321 1996

[2] K Kumar ldquoCeramic capacitors an overviewrdquo Electronics Infor-mation Planning vol 25 no 11 pp 559ndash582 1998

[3] J F Scott ldquoStatus report on ferroelectric memory materialsrdquoIntegrated Ferroelectrics vol 20 no 1ndash4 pp 15ndash23 1998

[4] A B Alles and V I Burdick ldquoGrain boundary oxidation inPTCR barium titanate thermistorsrdquo Journal of the AmericanCeramic Society vol 76 no 2 pp 401ndash408 1993

[5] Z Zhi-Gang Z Gang W Ming and Z Zhong-TaildquoTemperauture-humidity-gas multifunctional sensitiveceramicsrdquo Sensors and Actuators vol 19 no 1 pp 71ndash81 1989

[6] M Mori T Kineri K Kadono et al ldquoEffect of the atomic ratioof Ba to Ti on optical properties of gold-dispersed BaTiO

3thin

filmsrdquo Journal of the American Ceramic Society vol 78 no 9pp 2391ndash2394 1995


[7] H Song S X Dou M Chi H Gao Y Zhu and P YeldquoStudies of shallow levels in undoped and rhodium-dopedbarium titanaterdquo Journal of the Optical Society of America BOptical Physics vol 15 no 4 pp 1329ndash1334 1998

[8] C Buchal and M Siegert ldquoFerroelectric thin films for opticalapplicationsrdquo Integrated Ferroelectrics vol 35 no 1-4 pp 1ndash102001

[9] D Mahgerefteh and J Feinberg ldquoShallow traps and the appar-ent sublinear photoconductivity of photorefractive bariumtitanaterdquo Modern Physics Letters B vol 5 no 10 pp 693ndash7001991

[10] J XuW Zhang and Z Yang ldquoAn optical humidity sensor basedon Ag nanodendritesrdquo Applied Surface Science vol 280 pp920ndash925 2013

[11] X Wang and X Liu ldquoSelf-assembled synthesis of Ag nanoden-drites and their applications to SERSrdquo Journal of MolecularStructure vol 997 no 1ndash3 pp 64ndash69 2011

[12] L K Templeton and J A Pask ldquoFormation of BaTiO3from

BaCO3and TiO

2in Air and in CO

2rdquo Journal of the American

Ceramic Society vol 42 no 5 pp 212ndash216 1959[13] A Beauger J C Mutin and J C Niepce ldquoSynthesis reaction

of metatitanate BaTiO3mdashpart 2 Study of solid-solid reaction

interfacesrdquo Journal of Materials Science vol 18 no 12 pp 3543ndash3550 1983

[14] B A Hernandez K-S Chang E R Fisher and P K DorhoutldquoSol-gel template synthesis and characterization of BaTiO

3and

PbTiO3nanotubesrdquo Chemistry of Materials vol 14 no 2 pp

480ndash482 2002[15] G Pfaff ldquoSol-gel synthesis of barium titanate powders of various

compositionsrdquo Journal of Materials Chemistry vol 2 no 6 pp591ndash594 1992

[16] T Hoffmann T Doll and V M Fuenzalida ldquoFabrication ofBaTiO

3microstructures by hydrothermal growthrdquo Journal of

the Electrochemical Society vol 144 no 11 pp L292ndashL293 1997[17] P K Dutta R Asiaie S A Akbar and W Zhu ldquoHydrothermal

synthesis and dielectric properties of tetragonal BaTiO3rdquoChem-

istry of Materials vol 6 no 9 pp 1542ndash1548 1994[18] M P Pechini ldquoBarium titanium citrate barium titanium and

processes for producing samerdquo Patent US 3231328 1996[19] S Wada M Narahara T Hoshina H Kakemoto and T

Tsurumi ldquoPreparation of nm-sized BaO3particles using a

new 2-step thermal decomposition of barium titanyl oxalaterdquoJournal ofMaterials Science vol 38 no 12 pp 2655ndash2660 2003

[20] J-G Kim J-G Ha T-W Lim and K Park ldquoPreparationof porous BaTiO

3-based ceramics by high-energy ball-milling

processrdquoMaterials Letters vol 60 no 12 pp 1505ndash1508 2006[21] Y Hotta K Tsunekawa T Isobe K Sato and K Watari ldquoSyn-

thesis of BaTiO3powders by a ball milling-assisted hydrother-

mal reactionrdquoMaterials Science and Engineering A vol 475 no1-2 pp 12ndash16 2008

[22] V Vinothini P Singh and M Balasubramanian ldquoSynthesisof barium titanate nanopowder using polymeric precursormethodrdquoCeramics International vol 32 no 2 pp 99ndash103 2006

[23] S Ghosh S Dasgupta A Sen and H S Maiti ldquoSynthesisof barium titanate nanopowder by a soft chemical processrdquoMaterials Letters vol 61 no 2 pp 538ndash541 2007

[24] Y J JungD Y Lim J S Nho S B Cho R E Riman andBWooLee ldquoGlycothermal synthesis and characterization of tetragonalbarium titanaterdquo Journal of Crystal Growth vol 274 no 3-4 pp638ndash652 2005

[25] A V Ragulya O O Vasylkiv and V V Skorokhod ldquoSynthesisand sintering of nanocrystalline barium titanate powder undernonisothermal conditions I Control of dispersity of bariumtitanate during its synthesis from barium titanyl oxalaterdquoPowderMetallurgy andMetal Ceramics vol 36 no 3-4 pp 170ndash175 1997

[26] J Bera and D Sarkar ldquoFormation of BaTiO3from barium

oxalate and TiO2rdquo Journal of Electroceramics vol 11 no 3 pp

131ndash137 2003[27] W S Claubaugh E M Swiggard and R Gilchrist ldquoPreparation

of barium titanyl oxalate tetrahydrate for conversion to bariumtitanate of high purityrdquo Journal of Research of the NationalBureau of Standards vol 56 no 4 pp 289ndash291 1956

[28] M Stockenhuber H Mayer and J A Lercher ldquoPreparationof barium titanates from oxalatesrdquo Journal of the AmericanCeramic Society vol 76 no 5 pp 1185ndash1190 1993

[29] M Z C Hu G A Miller E A Payzant and C J RawnldquoHomogeneous (co)precipitation of inorganic salts for synthesisof monodispersed barium titanate particlesrdquo Journal of Materi-als Science vol 35 no 12 pp 2927ndash2936 2000

[30] W Lu M Quilitz and H Schmidt ldquoNanoscaled BaTiO3pow-

ders with a large surface area synthesized by precipitation fromaqueous solutions preparation characterization and sinteringrdquoJournal of the European Ceramic Society vol 27 no 10 pp 3149ndash3159 2007

[31] K M Hung W D Yang and C C Huang ldquoPreparation ofnanometer-sized barium titanate powders by a sol-precipitationprocess with surfactantsrdquo Journal of the European CeramicSociety vol 23 no 11 pp 1901ndash1910 2003

[32] A Testino M T Buscaglia M Viviani V Buscaglia and PNanni ldquoSynthesis of BaTiO

3particles with tailored size by

precipitation from aqueous solutionsrdquo Journal of the AmericanCeramic Society vol 87 no 1 pp 79ndash83 2004

[33] J M Bind T Dupin J Schafer and M Titeux ldquoIndustrialsynthesis of coprecipitated BaTiO

3powdersrdquo Journal Metals

vol 39 no 8 pp 60ndash61 1987

Submit your manuscripts athttpwwwhindawicom

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Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


the polymeric precursor method [22] the soft chemicalprocess [23] the glycolthermal method [24] and the copre-cipitation method [25] Among these the coprecipitationmethod is superior to othermethods in terms of the followingcharacteristics high growth rate modest equipment lowprocessing temperature ease of controlling the yield lowcost large amount synthesized and high quality [26]

In the coprecipitationmethod the preparation of BaTiO3

nanoparticles through the coprecipitation of barium and tita-nium hydroxides from aqueous solutions has been reportedsince the early Flaschen research work [27] Synthesis ofBaTiO

3nanoparticles as the decomposition product of bar-

ium titanyl oxalate or barium titanyl citrate is a multistageprocess depending on the gaseous medium the dispersionof the starting reagents and intermediate phase (the degree ofbranching of the interphase surface) the regime in which thereaction occurs (kinetic or diffusion) the growth tempera-ture and the heating rate [28ndash32] Although these previousstudies succeeded in fabricating BaTiO

3nanoparticles the

procedure is quite complicated Furthermore these proce-dures also require special conditions such as judicious choiceof the stabilizer heat treatment and time durationThereforeit will be a significant challenge to simplify the procedure forthe fabrication of BaTiO

3nanoparticles

In our laboratory we developed a simple procedureby slightly modifying the multistage process so it couldbe applied to fabricate BaTiO

3nanoparticles with well-

controlled size In this simple procedure appropriate amountof stock solution of titanium tetrachloride (TiCl

4) barium

chloride (BaCl2) and oxalic acid was added in deionized

water to form growth solution The BaTiO3nanoparticle

was formed by coprecipitation of both barium and titaniumprecursor During the coprecipitation process titanium actedas the seed in the growth solution so that the barium couldnucleate and precipitate onto the surfaces of titanium viathe heterogeneous nucleation process More importantly itis found that the amount of added BaCl

2can be critical for

shape and size of BaTiO3nanoparticles

In this study we first reported the fabrication of BaTiO3

nanoparticles with novel dendrite-like structures through thecoprecipitation method the so-called BaTiO

3nanodendrites

(BTNDs) It can be observed that the various amounts ofadded BaCl

2during nucleation and growth process caused

the alteration of the BaTiO3nanoparticles shape forming

the branch-like structures Until now to our knowledgethere are no reports yet on the synthesis of the BTNDsby coprecipitation method A good understanding of themicrostructure properties is a very important issue for thepotential application of the BTNDs Thus a detailed modelfor the newly observed novel BTNDs is also proposed toexplain their possible formation mechanism

2 Experimental Details

Barium chloride (BaCl2sdot2H2O 99) and oxalic acid

(C2H2O4sdot2H2O 99) were obtained from Riedel-deHa en

(Sigma-Aldrich USA) Titanium tetrachloride solution

(TiCl4 99 01M) was purchased from Fluka (Sigma-

Aldrich USA) All chemicals and materials were usedwithout further purification The distilled water usedthroughout the experiments was purified by a Milli-Qsystem (Millipore resistivity 182MΩ cm) The BTNDs werefabricated by first dissolving BaCl

2in distilled water at 50ndash

70∘C Separately oxalic acid was dissolved in distilled waterat 65∘C in an ultrasonic tank with titanium tetrachlorideslowly added The two solutions were mixed in an ultrasonicbath at 65∘C Nanometer-sized BaTiO

3particles were formed

at this stage Finally the growth time was 20minThe size and shape of the BTNDsweremeasured and ana-

lyzed by transmission electronmicroscopy (TEM JEOL JEM-1230) at an accelerating voltage of 80 kV The microstructureof the BTNDs was observed by high-resolution transmissionelectron microscopy (HRTEM Philips Tecnai G2 F20) withan accelerating voltage of 200 kVThe HRTEMwas equippedwith selected area electron diffraction (SAED) and an energy-dispersive X-ray (EDX) spectrometric element analyzer Thesamples for TEM SAED and EDX were prepared by dropcoating onto a standard 200-mesh 3mm carbon-coatedcopper grid (Agar Scientific UK)

3 Results and Discussion

Figures 1(a)ndash1(d) show the TEM images of BaTiO3nanoparti-

cles obtained by adding 3 4 5 and 6mL of BaCl2The results

clearly show that the shape of the BaTiO3nanoparticles can be

changed by altering the amount of BaCl2 When the amount

of BaCl2was 3mL the BaTiO

3nanoparticles with large

quantities were almost spherical in shape and were small insize as shown in Figure 1(a)The inset of Figure 1(a) shows theTEM image of BaTiO

3nanoparticles at higher magnification

indicating that the particle size is about 20 nm When theamount of BaCl

2was increased from 4 to 5mL the shape

of BaTiO3nanoparticles began to change from spherical to

dendrite-like as shown in Figures 1(b) and 1(c) When theamount of BaCl

2was 6mL the BaTiO

3nanoparticles were

almost dendrite-like in shape as shown in Figure 1(d) Evenafter sonication for TEM sample preparation the branches ofthe dendrites were intact indicating strong bonding betweenthe grains Thus there is not any isolated spherical BaTiO

3

particles in TEM image However the role of BaCl2may

be to act as shape-modifier to change BaTiO3nanoparticlesrsquo

shape from spherical to dendrite-like structure when theBaCl2with high amountwas added to growth solution during

coprecipitation process Besides these results also show thatthe size of BaTiO

3nanoparticles increased as the amount of

BaCl2increased as revealed TEM analysis (Figure 1)

Figure 2 shows the low-magnification TEM images ofsingle BTND prepared with 6mL of BaCl

2 As can be seen

in Figure 2(a) the BTND described as dendritic structureshas a large area of several square micrometers The thicknessof the central stem of BTND was sim300 nm Along thecentral stem (with length of sim20120583m) branching was seenfor every sim300 nm The lengths of the side branches werefound to be different for the same BTND Also the anglebetween the main stem and the branch was not constant





(a) (b)

(c) (d)


chloride




3



(a) (b)

(c)

1 1

2 2

3 3

4 4

5 5

6 6

7 7

8 8

9 9

10 10

11 11

Growth

Large particle

Small compounds


(d)



3com-






3










2can be




ount

s

Energy (keV)

400

200

0

0 5 10 15

C

O

CuCu

CuCuCu

Ba

Ba Ba Ba

TiTi

Ti




4and BaCl

2




3


3




2increases




3








2









3








2addition is still

under investigation

4 Conclusions





3compounds between



3particles




Acknowledgments


References







3thin









BaCO3and TiO

2in Air and in CO






3and











































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







(a) (b)

(c) (d)


chloride




3



(a) (b)

(c)

1 1

2 2

3 3

4 4

5 5

6 6

7 7

8 8

9 9

10 10

11 11

Growth

Large particle

Small compounds


(d)



3com-






3










2can be




ount

s

Energy (keV)

400

200

0

0 5 10 15

C

O

CuCu

CuCuCu

Ba

Ba Ba Ba

TiTi

Ti




4and BaCl

2




3


3




2increases




3








2









3








2addition is still

under investigation

4 Conclusions





3compounds between



3particles




Acknowledgments


References







3thin









BaCO3and TiO

2in Air and in CO






3and











































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

(c)

1 1

2 2

3 3

4 4

5 5

6 6

7 7

8 8

9 9

10 10

11 11

Growth

Large particle

Small compounds


(d)



3com-






3










2can be




ount

s

Energy (keV)

400

200

0

0 5 10 15

C

O

CuCu

CuCuCu

Ba

Ba Ba Ba

TiTi

Ti




4and BaCl

2




3


3




2increases




3








2









3








2addition is still

under investigation

4 Conclusions





3compounds between



3particles




Acknowledgments


References







3thin









BaCO3and TiO

2in Air and in CO






3and











































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




ount

s

Energy (keV)

400

200

0

0 5 10 15

C

O

CuCu

CuCuCu

Ba

Ba Ba Ba

TiTi

Ti




4and BaCl

2




3


3




2increases




3








2









3








2addition is still

under investigation

4 Conclusions





3compounds between



3particles




Acknowledgments


References







3thin









BaCO3and TiO

2in Air and in CO






3and











































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










BaCO3and TiO

2in Air and in CO






3and











































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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