roxana piticescu busteni 2006 - imnr.ro piticescu_busteni_ 200… · performance parameters of all...

WORKSHOP VIZGRAF, OCTOBER, BUSTENI, WORKSHOP VIZGRAF, OCTOBER, BUSTENI, 20062006

Roxana M. Roxana M. PiticescuPiticescu, , MadalinaMadalina L.PopescuL.Popescu

National R&D Institute for NonNational R&D Institute for Non--Ferrous and Rare Metals, Ferrous and Rare Metals, PantelimonPantelimon, , IlfovIlfov, ROMANIA, ROMANIA

LarisaLarisa GrigorievaGrigorieva, Institute of Solid State Physics, Institute of Solid State Physics--University of Riga, LatviaUniversity of Riga, Latvia

EugeEugeniu Vasile, METAV CD SA Bucharest, Romania

IMNR


Presentation contentPresentation content

IntroductionAim of the researchSWOT analysis of hydrothermal proceduresHydrothermal synthesis and characterization of BST

nanomaterialsConclusions and future works


Nanomaterials – the driving force, by Michael J. Pitkethly, Market Report, December 2004.

The primary of nanomaterials companies material product types and primary market focuses of nanomaterials companies

Nanomaterials market: 490 billion dollars in 2004 and 900 billion dollars in 2005 and 11 trillion dollars in 2010 (annual average grown rate > 10%)


In the last ten years the miniaturisation became a priority in the microelectronic field.

Ceramic materials with a low to moderate permittivity and the lowest loss angle are required for tunable devices. BST based materials are used for such devices.

Studies on the effect of grain sizes on the dielectric properties of BaxSr1-xTiO3 (BST) solid solutions at 100 KHz demonstrated that for x=0,3; 0,5; 0,7 Curie temperature (TC) and relative permittivity decreased with the grain sizes decreasing, phase transition being diffused.

It is therefore required to study the grain size effect on the dielectric properties of this ferroelectric materials.

Performance parameters of all these devices are dependent on the physical or chemical characteristics (stoichiometry, particles sizes, granulometric distribution and phase purity).

Different chemical synthesis methods of BST were tested (sol-gel procedure, co precipitation, hydrothermal synthesis) to achieve the desired applications.

S.Tusseau-Nenez, J.P.Ganne, M.Maglione, A.Morell, J.C.Niepce, M.Pate, J.Eur. Ceram.Soc., 24 (2004), 3003-3011S.B. Deshpande et al., Mat.Letters, 59 (2005), 293-296


Introduction

Aim of the researchSWOT analysis of hydrothermal proceduresHydrothermal synthesis and characterization of BST



The aims of the experimental laboratory work were:

• To develop a reliable method for hydrothermal synthesis of BST nanopowders starting from the precursor system BaCl2-TiO2Cl2-Sr(NO3)2 with increased stability in the solution phase

• To study the influence of grain sizes on some properties of BST sintered materials and to find a possible answer to the question if the use of nanostructures can improve the control of ferroelectric and dielectric properties of BST systems.

• Finally the results thus obtained to be used both to identify processing nanomaterials difficulties and the way to improve synthesis technology of nano-structured bulk BST materials.


IntroductionAim of the research

SWOT analysis of hydrothermal procedures

Hydrothermal synthesis and characterization of BST nanomaterials

Conclusions and future works


Hydrothermal reactions: chemical processes at high pressures and temperatures over the boiling temperature in aqueous solutionsSolvothermal reactions: chemical processes at high pressures and temperatures in non-aqueous solutions

Hydrothermal reactions between species in hydrothermal solutionsHydrothermal reactions between species in hydrothermal solutionsxM1(n)+(aq) +y M2(m)+(aq) +(x+y)OH-(aq) = xM1yM2O3 + 3(x+y)H2O;

Hydrothermal crystallisation:: M(OH)n = MOM(OH)n = MOn/2n/2 +(n/2) H2O+(n/2) H2O

•One step process•Minimize energy consumption•Closed systems, low environmental impact•Products with much higher homogeneity than solid state processingM.Yoshimura, W.Suchanek, Solid State Ionics 98 (1997), pp. 197-208

STRENGTHS OF HYDROTHERMAL SYNTHESIS


STRENGTHS OF HYDROTHERMAL SYNTHESISAny shape, any size (combining with other external driving forces, e.g. electrochemical)

U/I

Cathode

Reference Anode 0

100

200300

400500 0

20

40

60

80

100

120

log

K

Temperature, deg.C

PT; PZ; ST; BT

Electrophoretic deposition

Hydrothermal deposition

PT; PZ; ST; BT

R.R. Piticescu, R.M. Piticescu, Workshop COST D30, Turin, 26-28 Feb. 2004


WEAKNESSES

• Prediction: Thermodynamic data (only for ideal solutions, low valence ions)

•Kinetic limitations

νJi is the stoechiometric coefficient of species “i” in the reaction “j”

G0f is the standard free enthalpy of formation of reacting species AJ

i

mAi is the molar concentration of species Ai the solution

γi is the activity coefficient

qH])OH()OH(M[])OH(M[m )qmz(qqmn2

p,Tzn +⎯⎯ →⎯ +−

−+

∑=

υ=−nJ

1i

Ji

0f

Jij )A(GKlnRT ∏

=

=nJ

i

JiAiAiJ mK

1

,)( υγ log γAi = ΔHi +BZi + Pi

0 5000 1 .10 4 1.5 .10 40

50

100100

0

Fc t( )

150000 t

200C

3/1)1(1 α−−=ftt

R.R. Piticescu, C. Monty, D. Taloi, D. Millers, Sensor and Actuators B, 109 (1), 102-6 (2005)

0

10

20

30

40

50

0 2 4 6 8 10

Time (h)

D (n

m)

-ln (1-α)= kt m

Roxana M. Piticescu, R. R. Piticescu, D.Taloi, V. Badilita,Nanotechnology vol. 14 (3), pp. 312-17 (2003)

0 5000 1 .10 4 1.5 .10 40

50

70

0

Fc t( )

150000 t

125C

α=ftt


OPPORTUNITIES

VERSATILITY:Oxides, non-oxides, organic/biologic materials; hybrid materialsHYDROTHERMAL SYNHTESIS IS ONE OF THE VERY FEW METHODS ABLE TO GENERATE NEW MATERIALS OR MATERIALS WITH RADICALLY NEW PROPERTIES

Recent examples: ultra-hard materials doped for semiconductor ( p and n doped cubic-BN)[1, 2]or opto-electronic (e.g. cubic-Si3N4)[3] applications,. ANi3+0.98Fe0.02O3 (A=Nd, Lu) perovskites [4]New physical phenomena may be found, for example the perovskite BiNiO3 (prepared at 60 kbar, 1000 °C) shows a unique transition between a metallic and insulating state[5]

[1] Solozhenko,V. L., Dub, S. N. & Novikov, N. Diamond Relat.Mater. 10, 2228–2231 (2001)[2] Taniguchi, T. et al. Jpn. J.Appl. Phys. 241, L109–L111 (2002).[3] I.A.Presniakov, G.Demazeau, A.V.Baranov, A.V.Sobolev, K.V.Pokholok., Phys. Rev. B71, 2005, 054409[4] Gryko, J. et al. Phys. Rev. B 62, 7707–7710 (2000).[5] Ishiwata S, Azuma M, Takano M, et al, J. Mater. Chem. 12, 3733 (2002).

76. R.M. Piticescu et al.. Solid State Phen, 106 (2005) p47-57

New hybrid inorganic-organic nanomaterials by the effect of high pressures on the atomic distance [6]


Thin films nucleation and growth-surface diffusion- continuous growth at the kinks

)( 022adc cj

FzRT

dtd

αη

=

-Formation of clusters and critical nuclei- Formation of monolayrers by layer to layer growth

W(t) = W0 ( 1 - ekt )

Types of morphologies

-Layer or platelate growth- Pyramidal growth-Whiskeres-Dendrites-Epitaxial growth on crystalline substrates-Oriented growth on polycrystalline or amoprphoussubstratesUnpredictible!


ΔVt

+kT

-kT

H

ΔV repulsion

ΔV atraction

ΔV total

THREATSPhase separation: additives for agglomeration/de-agglomeration (steric or electrostatic effects) Processing: fine, nanocrystalline powders require high pressures to be compacted special forming technologies

lack of reliable and standardised characterisation methods;

anxiety of end-users vis-à-vis of environmental problems related to nanopowders manipulation

fluidelastomer

( )PC ab

Pa

=− +1


IntroductionAim of the researchSWOT analysis of hydrothermal procedures

Hydrothermal synthesis and characterization of BST nanomaterials



SynthesisBaCl2, TiO2Cl2, Sr(NO3)2 aqueous solutions starting materials + mineraliser reagent (KOH).

Hydrothermal treatment in Teflon vessel of the CORTEST, USA digitally controlled autoclave.

ProcessingBinding with polyvinyl alcohol, granulated and pressed at 800 MPa.

Sintering 2 hours, at 1250 and 1300oC,heating rate of 5oC/min, in a CARBOLITE RHF 17/3 furnace.

Density of green and sintered pellets - standard Archimedes method.

CharacterisationChemical composition using AAS and ICP

XRD - SHIMADZU XRD 6000 apparatus with the data acquisition

SEM/EDS - HITACHI model S-2600N;

TEMBF, SAED and HRTEM - Philips CM 12 electronic microscope

Cathodic luminescence of sintered BST: electron-beam apparatus (excitation power max. 270 kV),

excitation times between 5 to 15 ns, FEP-100 UV photomultiplier, FEP 83 detector for the R-IR region.

Dielectric constants measured after covering with Ag paste using HP 4284A LCR meter.


Molar ratio Ba+Sr / Ti =1 ;pressing 800 MPa;

sintering 1300OC/2hours

BST 7 P 7, 8,10,11

Molar ratio Ba+Sr / Ti =1.13 ; pressing 800 MPa;


B 2 P 36, 37,

39, 42

Molar ratio Ba+Sr / Ti =1.13 ; pressing 800 MPa;


B 2 P 22, 26, 27,

29,30

Processing conditions Sample

BST 7 P 7, 8,10, 11

B 2 P 36, 37,39,42

- Ba0,6Sr0,4TiO3 major phase; main maximum (011) (angle 2θ =31,94); d = 2,81Å- BaTiO3 >10 % with crystalline cubic phase; main maximum (110) (angle 2θ

=31,34); ao = 4.033Å- Ba4Ti13030 minor phase; main maximum (131) (angle 2θ =28,34); crystalline

orthorhombic structure; lattice parameters a0 = 17,06 Å ; b0 = 9,864 Å and c0 = 14,05 Å

B 2 P 22, 26, 27, 29, 30,

Phase analysis Sample

20 30 40 50 60 70 800

500

1000

1500

2000

2500

3000

3500

4000

4500

Inte

nsity

(a.u

.)

2 θ

B2P22 Ba0.6Sr0.4T iO3


Sample B2P29 Thermal etched 1200 CBa+Sr / Ti =1.13 /1250 CGrains containing crystallites with a large dimension distribution (100 to 500 nm)

Sample B2P42Thermal etched 1200 C

Ba+Sr / Ti =1.13 /1300 CCrystallites dimension distribution narrower (about 100 nm)

Sample BST7P10Thermal etched 1200 CBa+Sr / Ti =1/1300 CGrain sizes 0.1-1μm. Each grain is formed by crystallites under 100 nm


TEM image of samples B2P26 and P27 (Ba+Sr / Ti =1.13 ; 800 MPa; 1250OC/2hours

Structural or ferroelectricnanodomains?


TEM image for sample B2 P36Ba+Sr / Ti =1.13 /1300 C SAED image associated to

micro-area for sample B2 P36

Partial conclusions – microstructure

•Some cubic phase probably due to the hydrothermal synthesis conditions.

•In hydrothermal conditions the formation of metastable crystals with minimum superficial energy is increased (Ostwald’s rule).

Or:

•Nanometric size of the crystalline grains stabilise the cubic phase.


-20 0 20 40 60 80 100 1200.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40 1-100 Hz2-1000 Hz3-10000 Hz4-100000 Hz5-1000000 Hz

54

3

2

1tgδ

T, 0C

BST7P11

-20 0 20 40 60 80 100150

152

154

156

158

160

162

164

166

168

170

1722

34

5 1-no2-1000 Hz3-10000 Hz4-100000 Hz5-1000000 Hz

ε

T, 0C

B2P30

-20 0 20 40 60 80 100 1200.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40 1-100 Hz2-1000 Hz3-10000 Hz4-100000 Hz5-1000000 Hz

54

3

2

1

tgδ

T, 0C

BST7P11

•The dielectric constant increased from ε~170 (sample B2P30) to ε~360 (sample BST7P11)•Lower values of the permittivity for both samples but consistent with other data (S.Tusseauet.al, J.Eur. Ceram.Soc., 24 (2004), 3003-3011= grain sizes effect


2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.80.00

0.05

0.10

0.15

0.20

0.25

BaSrTiO3_B2_P30RT; electron beam excitation

Lum

ines

cenc

e in

tens

ity, a

.u.

E, eV

5 ns 15 ns

2,0 2,2 2,4 2,6 2,8 3,0 3,20,00

0,02

0,04

0,06

0,08

0,10

0,12

0,14

0,16

0,18 BaSrTiO3B2_P3RT; e-beam excit.; no correction;FEP100

Lum

ines

cenc

e in

tens

ity

E, eV

5 ns 10. ns 20. ns

Cathodo-luminescence spectrum (electron beam excitation) with different delay times

1.0 1.5 2.0 2.5 3.0 3.5 4.00.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08 BST_ ceremicB7_P11RT, e-beam excitationFEP100, with correction

Lum

ines

cenc

e in

tens

ity

E, eV

FEP83 FEP100

Fundamental absorption

Excitation bands from 2.7 due to Sr-O bondExcitation band from 3.1 eV due to Ti-O bond. No defect band was observed. Slight differences between the ratio of their intensity



nanomaterials



1.5 μm

150 nm

300 nm

TaO

BST

CPW grosime 2μm Au

Membrana de Si

Curent distribution on shifter with Si membraneat 0 volts and 20 GHz

Curent distribution on shifter with Si membraneat 30 volts and 20 GHz


• Hydrothermal synthesis enables controlling the structure of BST materials at nanoscalelevel: materials with new and controlled properties may be produced for advanced applications.

•The main factor influencing the microstructure of sintered samples is Ba+Sr/Ti molar ratio

•Decreasing the Ba+Sr/Ti molar ratio lead to samples with a narrower crystallite sizedistribution of about 100 nm. HRTEM analysis relieved the presence of nanodomains

•Permittivity values are lower comparing to the existing literature data for micrometric materials probably due to the grain size effect

•Luminescence is dependent on the Ba+Sr/Ti molar ratio and it could be a useful and rapid method to control hydrothermal synthesis process

FUTURE WORKS•Thin films by hydrothermal – electrochemical method•Optimise composition/structure and study the role of nanodomains on electrical properties


CONTACT PERSONS CONTACT PERSONS

Dr.TeodorDr.Teodor VeleaVelea, General Director , General Director ee--mailmail : : [email protected]@imnr.ro

Dr. Dr. RoxanaRoxana PiticescuPiticescu, Lab. , Lab. HeadHeadee--mailmail : : [email protected]@imnr.ro

Dr. Robert Dr. Robert PiticescuPiticescu, Director Center for Technology , Director Center for Technology Transfer in Advanced MaterialsTransfer in Advanced Materials

ee--mail: mail: [email protected]@imnr.roPhone/faxPhone/fax : 0040: 0040--2121--352.20.48 / 352.20.45352.20.48 / 352.20.45Address: 102 Address: 102 BiruinteiBiruintei Blvd., Blvd., PantelimonPantelimon, , judetjudet IlfovIlfov, Romania, Romania


AcknowledgementsAcknowledgementsAcknowledgements

Thank you for your attention !

Nanostructured Materials Group – INCDMNR Pantelimon

Dr. Vismants Zaulus– Inst. Solid State Physics Riga

Dr. I. Sajin and Dr. M. Dragoman-Nat. Inst. Mycrotechnologies

Romanian Ministry for Education and Research in the frame of National Programme for New Materials, Micro and Nanotechnology,

Polar Electro ceramics Network (POLECER)

MINAEST- NET European project

EGIDE France – supporting the ECO-Net “Fun-Nanos” project

roxana piticescu busteni 2006 - imnr.ro piticescu_busteni_ 200… · performance parameters of all...

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