R. Anand Theerthan, Alla Artemenko U‐Chan Chung,Catherine Elissade &  Mario Maglione

Metz , 15 Nov 2012

115/11/2012

OutlinePart 1 – Fe doped Ba

Macroscopic:1. Domain wall relaxation in Fe doped BaTiO3 single crystals

I i h  i  KTiOPO   i l   t l   i l t i2. Ionic space charges in KTiOPO4 single crystals: piezoelectricresonance as a probe for ions accumulation at surfaces

3. Confirmation using SHG mapping3 g pp g4. Electronic space charges in BaTiO3 core‐shell composites : 

linking giant dielectric permittivity to local charged defects

Mi iMicroscopic:1. Polaron relaxation in Fe doped BaTiO3 single crystals

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RelaxationPart 1 – Fe doped Ba

R. Coelho, Physics of Dielectrics

315/11/2012

Charge Localisation in Single CrystalsPart 1 – Fe doped Ba

105105

BaTiO :ε1

104104

BaTiO3: 1. oxidized2104104

3

2. raw3. reduced

103103

1

2

102102

f = 1 kHz

100 200 400 600 800

100 200 400 600 800

Bidault et al. Phys.Rev.B 49, 7868 (1994)

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Is it possible to evidence such space charges at much lower temperatures?

Fe doped BaTiO3 Single crystalsPart 1 – Fe dopedBaTiO3

Iron doping to have heterovalent impurity

Substitution of  Ti4+ by Fe3+ leads to creation of oxygen vacancies

Localization of free charges at the domain walls

Schematic of localization of free charges at domainwalls

Under magnetic field this localization is disturbedUnder magnetic field this localization is disturbed

Physics of Dielectrics for the Engineer by R. Coelho, (1979)

515/11/2012

Magnetic Tuning of Domain Wall RelaxationPart 1 – Fe dopedBaTiO3

BTO:Fe 0.075 % BTO:Fe 0.3 %

Temperature governs the number of domains

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Ionic mobility in KTP

In Colloboration with Pr. Vincent Rodriquez (ISM)

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Potassium Titanyl Phosphate(KTiOPO4)Part 2 – Ionic mobility

in KTP

Paraelectric Ferroelectric

Ferroelectric transition at 1203 KKTP displays combination of Ferroelectric, piezoelectric, pyroelectric and    

superionic propertiesSuperionic transition is close to 200KMobility of potassium ions in the cavities along C axis is responsible for 

high ionic conductivity of KTP

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g

d2

Diapositive 8

d2 1. Talk about K role in ferroelectric transition,

at the end of this slide say - our goal is to establish a connection between ionic mobility and piezoelectric resonance since potassiul ion is involved in both.Dayalu; 05/10/2011

Conductivity MeasurementPart 2 – Ionic mobilityin KTP

0.48eV

At 200K KTP stops being an ionic conductor.

Conductivity can be measured only along c axis 

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Pyroelectric MeasurementPart 2 – Ionic mobilityin KTP

Electroded face

Pyroelectric cofficient ‐ 2.3 nC cm‐2 K‐1Pyroelectric cofficient 2.3 nC cm K

P. Urenski and G. Rosenman, J.Phys D: Appl. Phys. 33 (2000) 2069

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Splitting of PiezoresonancePart 2 – Ionic mobilityin KTP

Electroded face

c

Electroded face

a

Length ModeLength Mode

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Splitting of Piezoresonance…ContdPart 2 – Ionic mobilityin KTP

El d d fElectroded face

Thickness Mode

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Origin of SplittingPart 2 – Ionic mobilityin KTP

b

a

Domain Wall orientation

Splitting happens in all directions.

Multitude of domains can cause only broadening but not splitting

Hence domains are not at the origin of splitting

1315/11/2012 P Pernot‐Rejmàkovà et al, J. Phys.: Condens. Matter,  15 (2003) 1613

Origin of splitting…. contdPart 2 – Ionic mobilityin KTP

Bias Experiment:

KTP

400 V/cm

Field cooling

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Macroscopic Ionic Space ChargePart 2 – Ionic mobilityin KTP

S li i i i i i  (  K) i d    b ild   f 

A.Theerthan et alPhys. Rev. B 85, 024103 (2012)

Splitting at superionic transition (200 K) is due to build up of spacecharge which change the elastic compliance.

Tuning of piezoresonance splitting under an electric field corroborates

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the above argument

ConfirmationPart 2 – Ionic mobilityin KTP

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RecapPart 2 – Ionic mobilityin KTP

KTP undergoes superionic transition at 200 K

At the same temperature piezoelectric resonanced   ll d fi d littiundergoes a well defined splitting

Building up of ionic space charges in the single crystals isBuilding up of ionic space charges in the single crystals isat the origin of the splitting.

How to probe space charge in KTP ? 

1715/11/2012

How to probe space charge in KTP ? 

Part 2 – SHG Mappingin KTP

1815/11/2012

Basics of SHGPart 2 – SHG Mappingin KTP

Non centrosymmetric

Output frequency = 2 x Incident frequency

Output wavelength = ½ x Incident wavelength

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Output wavelength = ½  x Incident wavelength

Probing of Space Charge in GlassesPart 2 – SHG Mappingin KTP

Local centrosymmetry of glasses is broken under an electric field

Example: Soda lime glass (SiO2 + Na2O + CaO + MgO + K2O + Al2O3)

1.5 kV

Air poledAir poled

SHG i f l t   b   h

2015/11/2012

SHG is very useful to probe space charges.

Marc Dussauze et al; J. Phys. Chem. C, 114 (2010) 12754

SHG Mapping of BaTiO3 Single CrystalPart 2 – SHG Mapping

in KTP

In BaTiO3 no ionic conductivity unlike KTP

Surface Surface MapMap In In DepthDepth MapMap-40

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SHG Mapping of Unpoled KTPPart 2 – SHG Mappingin KTP

Surface Surface MapMap-25‐25273 K

In In DepthDepth MapMap293 K 200 K

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Periodically Poled KTP (PPKTP)Part 2 – SHG Mappingin KTP

What is Periodically Poled KTP ?bb

a

c

2315/11/2012 Thesis: Carlota Canalias, 2005 

SHG Mapping of PPKTPPart 2 – SHG Mappingin KTP

b Surface mapSurface Surface MapMap

298 K 233 K-1.0

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SHG Mapping of PPKTPPart 2 – SHG Mappingin KTP

b In Depth map In In DepthDepth MapMap298 K 233 K

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In Depth Map Continued….Part 2 – SHG Mappingin KTP

SHG SHG mappingmapping of of domainsdomains withwith temperaturetemperatureb In Depth map

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2615/11/2012 Domain Domain wallswalls

General ConclusionPart 2 – SHG Mappingin KTP

Splitting of piezoresonance in KTP isattributed to build up of space charges

Localization of free charges on the domainwalls inside KTP crsytals was observed.

Both unpoled and PP KTP go to a minimum in SHG intensity around 200 K – 230 K, the temperature range where conducitivty starts to slow down.

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OutlinePart 1 – Fe doped Ba

Macroscopic:1. Domain wall relaxation in Fe doped BaTiO3 single crystals

I i h  i  KTiOPO   i l   t l   i l t i2. Ionic space charges in KTiOPO4 single crystals: piezoelectricresonance as a probe for ions accumulation at surfaces

3. Confirmation using SHG mapping3 g pp g4. Electronic space charges in BaTiO3 core‐shell composites : 

linking giant dielectric permittivity to local charged defects

Mi iMicroscopic:1. Polaron relaxation in Fe doped BaTiO3 single crystals

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Control of interfaces in ceramicsPart 3: BTO Ceramics

Coating of individual particlesBaTiO @SiOBaTiO3@SiO2

200nm200nm

200nm

50 nm50nm

control of the design at the nanoscalecontrol of the design at the nanoscaleleading a loss barrierlimited interdiffusion and grain growth during sinteringlimited interdiffusion and grain growth during sintering

Mornet, S. and coll., Chem. Mater. 2005, 17, 4530

Hubert, C. and coll., Ceram. Int. 2004, 30, 1241Chen, R. Z. and coll., Mater. Lett., 2002, 54, 314

29

Control of Free chargesPart 3: BTO @ SiO2Ceramics

Spark Spark Plasma Sintering under reducing Plasma Sintering under reducing conditionsconditionsconditionsconditions

Spark Plasma Sintering (SPS)BaTiO3@SiO2

Sintering

BaTiO   00 nm

ReducingConditions

20nm

T= 1100ºC; t= 3’; Atm.: Vacuum; P= 50 MPaBaTiO3= 500 nmSiO2= 5 nm

Post AnnealingT= 800ºC; t= 10h; Atm.: Air

Papyex BaTiO3@SiO2

30M.Maglione ISAF‐ECAPD‐PFM 07/2012

Evidence for Free ChargesPart 3: BTO @ SiO2Ceramics

Blue color due to reduction of Ti4+ to Ti3+COATED COATED 

UNCOATED UNCOATED 

A t k t  l A l  Ph  L tt      ( )Artemenko et al Appl. Phys. Lett. 97, 132901 (2010)

31M.Maglione ISAF‐ECAPD‐PFM 07/2012

Gaint PermittivityPart 3: BTO @ SiO2Ceramics

‐Giant Permittivity: ε’= 120000 – 140000Giant Permittivity: ε  120000  140000‐Low Stable Dielectric Losses: tan δ= 5%‐Ferroelectricity Not Cancelled: Tc= 400 K

Applied Physics Letters 2009, 94, 072903

32M.Maglione ISAF‐ECAPD‐PFM 07/2012

Gaint permittivity relaxationPart 3: BTO @ SiO2Ceramics

C(F)

Activation energy E= 0.1 eV

Applied Physics Letters 2009, 94, 072903

33M.Maglione ISAF‐ECAPD‐PFM 07/2012

Relaxation ProcessPart 3: BTO @ SiO2Ceramics

At hi h t t f h ( l t d tAt high temperatures, free charges (related to oxygen vacancies) can follow the alternating

l t i fi ld h l i ti i f ltelectric field : a space charge polarisation is feltwhich increase the low frequency permittivityAt low temperatures free charges are fullytrapped on lattice sites and the space charge polarisation can no more follow the alternatingelectric field : a dielectric relaxation occursMicroscopic evidence for this charge trapping?

34M.Maglione ISAF‐ECAPD‐PFM 07/2012

Microscopic evidence for free charge trapping : EPRPart 3: BTO @ SiO2Ceramics

35M.Maglione ISAF‐ECAPD‐PFM 07/2012

Temperature dependencePart 3: BTO @ SiO2Ceramics

100K

60K

100K

50K

20K

4K

36M.Maglione ISAF‐ECAPD‐PFM 07/2012

Activation energyPart 3: BTO @ SiO2Ceramics

A t k t  l A l  Ph  L tt      ( )

37

Artemenko et al Appl. Phys. Lett. 97, 132901 (2010)

M.Maglione ISAF‐ECAPD‐PFM 07/2012

Part 3: BTO @ SiO2Ceramics

Control of giant permittivity in Control of giant permittivity in h llh ll iiBaTiO3BaTiO3 core@shellcore@shell compositescomposites

Silicacoatingcoating

Enables coPrevents re-oxidation

Enables co-existence giant

permittivity/

Reduceslosses

p yferroelectricity

Chung et alAPL 2009, 94, 072903

3838

losses

OutlinePart 1 – Fe doped Ba

Macroscopic:1. Domain wall relaxation in Fe doped BaTiO3 single crystals

I i h  i  KTiOPO   i l   t l   i l t i2. Ionic space charges in KTiOPO4 single crystals: piezoelectricresonance as a probe for ions accumulation at surfaces

3. Confirmation using SHG mapping3 g pp g4. Electronic space charges in BaTiO3 core‐shell composites : 

linking giant dielectric permittivity to local charged defects

Mi iMicroscopic:1. Polaron relaxation in Fe doped BaTiO3 single crystals

15/11/2012 39

Polaron RelaxationPart 1 – Fe dopedBaTiO3

Electron Hopping

BTO:Fe 0.075 % BTO:Fe 0.3 %

4015/11/2012

Magnetic Tuning of Polaron RelaxationPart 1 – Fe dopedBaTiO3

20 K 30 K20 K 30 K

BTO: Fe 0 3 %70 K

BTO: Fe 0.3 %

4115/11/2012

ESR on Fe doped BaTiO3Part 1 – Fe dopedBaTiO3

Fe3+ surrounded by 6 Fe surrounded by 6 oxygen

VO ‐ Fe3+‐ VO

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Case of SrTiO3  and KTaO3Part 1 – Fe dopedBaTiO3

SrTiO3 KTaO3

Concentration of free charges are too low to realize the  magnetic tuning effect

4315/11/2012 O.Bidault, M.Maglione, M. Actis, M. Kchikech and B. Salce, Phys. Rev B 52 (1995) 4191

SummaryPart 3: BTO @ SiO2Ceramics

D     h   f d i ll d f   h  • Due to the presence of domain wall and free charges we can observe realxation at low temperaturesI i h l ff t th i l t i• Ionic space charges can also affect the piezoelectricproperties (Phys. Rev. B 85, 024103 (2012))

• Accumulation at surfaces as well as at domain walls is• Accumulation at surfaces as well as at domain walls isseen

• Space charges can greatly increase the dielectric• Space charges can greatly increase the dielectricparameters of ferroelectric (and other oxides)

• At the microscopic level polaron can be formed due toAt the microscopic level polaron can be formed due to free charges and that can be tuned by magnetic field

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4515/11/2012

NamasteNamaste

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Part 2 – SHG Mappingin KTP

Why Periodic Poling is important?

To maintain efficient energy transfer for non linearfrequency, the interacting waves must be in phase witheach other.Af i l h ll d h l h hAfter a certain length called coherence length the

interacting waves will go out of phase relative to eachother.

Argon poled

P f M hPerfect Match

PPKTP 

Mis Match

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