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Part 1Synthesis and design of Nanocrystals

Morphology Control ofMetal Oxide NanocrystalsNational Institute of Advanced Industrial Science and Technology(AIstMetal oxides have been widely used in electro devices, optical devices, etc Recently, liquidThis section describes liquid phasgrowth They showed highance of solution systems for future metal oxide deof anisotropic metal oxide particles and films wouldntribute to development ofxide science and technology2 Morphology control of acicular BaTiO3 particlesAcicular BaTiO particles were developed using solution systems The morphology of BaC2Otroducing Ti ions from the coprecipitated amorphous pcicular BaTiO particles haven aspechigh as 18 and the particle size can be controlled by varying the growthfactors(MLCC)indispensable electronic componentsadvanced electronic technology2-12, but largere needed forfuture electronic devices To meet these needs, BaTiO, partunsized bferroelectric ceramics lose their ferroelectricity when their particle size is decreased and loserely at a critical size2-11

This is known as the size effect and it impedes theprogress of MLCC, so a novel solution has been eagerlypose MLCC usingiO particles, An ultra-thin ferroelectric laynd high capacity can be realized by acicular particles having a high aspect ratio The shortide provides an ultra-thin ferroelectric layer and the large volume caused by the long sidecandidate fohas hestructure, anddifficult to control due to its isotropic crystal faces We focusedtriclinic BaC2O05H2O which has an anisotropic crystal structure and controlled themorphology of these particles by precisely controlling crystal growth We also achieved

phase transition of BaC0 5Hz0 to crystalline BaTiO, by introducing Ti ions from theeloped several key technologies,ccessfully able to produce anisotropic acicular BaTiO particled previously Additionallyalates(MCO4)have been used for synthesis of rod-shaped oxides or hydroxides Ylayashi et al reported preparation of rod-shaped BaTiO from rod-shaped TiO2-nH2O andBacOs in molten chloride at high temperatureh from McOa 2H2oNaoh solutionset al prepared flowerlike SnC2O,taining SnCl2 and oxalic acid Theannealed atmbient atmre to obtain flower like snOOxalic acid(252 mg) was dissolved into isopropyl alcohol (4 ml)(Fig 1) Butyl titanatenomer(0 122 ml) was mixed with the oxalic acid solution, and the soixed with distilled water(100 ml) The pH of the solution was increased to pH7 bhe volt150 ml by these additions The aqtution(50 ml) with barium acetate(393 mg)wasmixed with the oxald solution, The mixed solutitaining barium acetate (077d thethe collision of heucleated particles and destruction of largeoidef therder by changing the growth period Largeto evaluate thegy andstallinity in detaiystal growth of750cFig 1

Conceptual process for fabricating acicular BaTiO3 particles Morphology control ofC2O405H2O particles and phase transition to BaTiO Reprinted with permission fromRef Masuda, Y, Yamada, T and Koumoto, K 2008, Crysf Growth Des, 8, 169 CopyrightOxalate ions ( C2O42)react with bariuma2*)to form barium oxalate(BaC2O405HxO)BaC2O4·05Hacetate acid((CH3COO)2Ba), however, it can be deposPH 7 which is adjusted by adding NaoHBaC2oO4 0 5HyO was thus successfully precifrom the solutionwere on average 23 um(ranging from 19 to 27 um) in width and 167 umto 189 um)in length, giving a high aspect ratio of 72(Fig 2)Theyclear crystal faces, indicating high crystallinity A gel-like solid was also coprecipitated frthe solution as a second phase

rphology Control of Metal Oxide Nanocryst1習贈100um如450678d diffraction measp), XRD pattern calculated from crystal structure data16(second step) and XRDof JCPDS No 20-134(third step) are shown for triclinic BaC:O45H2O Reprinted withssion from Ref, Masuda, Y,, Yamada, T and Koumoto, K, 2008, Cryst Growthsharp diffraction peaks of crystalline BaC:O405H2O with no additional phase Acicularparticles were crystalline05H2O and the gel-like solid would bemorphousFortunately, BaC2 O40

5H2o has a triclinic crystal structure as shown by the modelcalculated from structure datal7(Fig 2 XRD first step) and thus anisotropic crystal growthalar shape Each crystal face hasurface energy and surface nature sueta potential and surface groups anisotroyrowth is induced by minimizing the total surface energy in ideal crystal growthAdditionally, site-selective adsorption of ions or molecules on specific crystal facespresses crystal growth perpendicular to the faces and so inanisotropic crystalgrowth Thes

e factors would cause anisotropic crystal growth of BaC2O405H2O and henceto contrond fabricate acicular bacH2o particles Thepositions of diffraction peaks corresponded with that of jCPDS No, 20-0134(Fig 2 XRDthird step) and that calculated from crystal structure dataI( Fig 2 XRDpared to their relative intensity The enhancement of diffraction intensity from specifianisotropic crystal growth, a large crystala specificrystal orientation increases the x-ray diffraction intensity for the crystal face perpendiculato the crystal orientationEDX elemental analysis indicated the chemical ratio of the precipitate, whichdicated that the coprecipitatedphous gel contained Ti ions Additional Ba ionsannealing and removed by hcl treatment in the nextratio was thus controlled to slightly above Ba /Ti=1 by adjusting the volume ratio oficular particles and gel-like solid Consequently, acicular particles of crystalline BaCo

Nanocrystal05H2O with Ti-containing gel-like solidprecipitated at pH2 noe particles of barium titanyl oxalate(BaTiO(C-M the reacmnocreactialic acid (H2 C2O4 2H20)with butyl titanate monomer(CHyO)Ti) and hydrolysis(CH,O) Ti +H, C,O: 2H,O- TiOC, O, 4C H, OH+H, OTiO(C2O4)was then converted to oxalo(H2TiO(C2O4)2)by the reaction:taining oxalotitanic acid(H2TiO(C:O4)2) formed by reaction(b) wasubjected to the following cation exchange reaction by rapidly adding an aqueous solutionHTiO(C,O )+ Ba(CH, COO,,BaTiO(C O )++ 2CH, COOlOn the other hand, neither BaC204 05H O nor BaTiO(C2Oa)z was precipitated at pH 3 toH6 Gel-like solid was formed in the solution and their XRD spectra showed no diffractionks The amorphous gel that precipitated at pH-3 to 6 would be the same as theamorphous gel coprecipitated at PHparisons show that the crystal growth and morpThe precipitate was annealed at 750C for 5 h in air Acicular BaC:O4 05H2Oreacted with Ti-containing amorphous gel to introduce Ticrystalline Baray diffraction of the annealed precipitate showed crystallinnd an additional barium carbonate phasef barium carbonate phaThe annealed precipitate was further immersed in HCl solution(1 M)to dissolve bariumcarbonate(BaCO) Acicular particles of crystalline BaTiOccessfully fabricated withBaTiO(Fig 3)

The high aspect ratio of the particlesthat of BaC3O4-05H2O particles The particld by the growth period and solution concentrationC2O4 05H2O precipitation which decides the particle size of BaC2O4-05H2OBaTiOj has a cubic crystal structure at high temperature above phase transition and has astal structure at room temperature The cubic crystal structure is completed the tetragonal crystal structure results from stretching a cubic lattice along onits lattice vectors For both of the crystal structures it is diffictcrystal growth, however, with oureveloped process we couldthe morphology and fabricate acicular particles This was achieved by controlling theby introducing Ti ions from the coprecipitated amorphous phase The novel concept can beplied to a wide variety of morphology control and crystal growth control for advancedmposed of crystalline materials

rphology Control of Metal Oxide NanocrystTetragonal BaTiO3E露Fig 3, SEM micrograph and XRD diffraction pattern of acicular BaTiO particles afternealing at 750C for 5 h and HCl treatment XRD diffraction measurement data(firstep) and XRD pattern of JCPDS No 05-0626(second step)are shown for tetragonal BaTiReprinted with permission from Ref Masuda, Y, Yamada, T and Koumoto, K, 2008,Cryst Growth Des,8, 169 Copyright @American Chemical Society3 Morphology control of Zno particlesnediamine(H2N-CH CH2-NH, 15-45 mM, Sigma-Aldrich)added to the zinctate aqueous solution(Zn(CH CoO)2 15 mM, Kishida Chemical Co, Ltd )to promoposition of Zno19

Zinc chelate(Zn(H2N-CH CH2-NH2 )2*)was formed from zinc acetatend ethylenediamine in reaction(a) ZnO was crystallized fromion(OH- )in reaction(c)Zn(CH, COO)+2H, NCH, CH, NH, EZn(H, NCH, CH, NH,CH COOZn(H, NCH, CH, NH,),+2OH -ZnO+2H, NCH CH, NH, +H, O) PH=80 or (c) pH=87, respectively Crystal growth rate andof znotemped to control to change particle morphology Si substratego Co Ltd )was immersed to evaluate deposited Znofilms The solution in a glass beaker was kept at 60C for 3 h using a water bath The siliconsubstrate was cleaned before inn as described in references, The substrate was rinsedwith distilled water after immerZno particles having hexagonal cylinder shape were homogeneously nucleated anddeposited in the aqueous solution containing 15 mM ethylenediamine (ethylenediamine[Zn]=(a)1: 1)( Fig, 4a), X-ray diffraction patterns showed the deposition torystallized ZnO(FiThe relative intensity of (10-10) and (0002) is similar to that ofrandomly dted Zno particles, indicating the random orientation of deposited Zno

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ContentsNanocrystals in Metallic Glasses5 Preparation of Nano alsos via Shocke Reprecipitation Method 165Koichi Baba winfriedOikawa and Hachiro nakanishiYoshitake may and Patterning of Nanocrystals 185Chapter 7 Self-aer 8 Synthesis and Characterization of dicomposite Cu-Al2OMaria Korac and Zeljko Kamberovic