Synthesis and Characterization of Ferroic Nanocomposites of Spinel

Ferrites and Perovskites

Jacob Faucheaux, Amin Yourdkhani, Shiva Adireddy, and Gabriel Caruntu*

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In this research, 0-­3 type ferroic nanocomposites have been fabricated using colloidal synthesis approaches. The zero dimensional (0D) magnetic phase (CoFe2O4) was synthesized by an elevated temperature hydrolysis reaction carried out in a three neck flask. The ferrites were incorporated into the matrix of the perovskite phases (ATiO3, A= Ba and Pb) by two methods. Lead titanate was deposited onto the ferrites in an aqueous solution via the liquid phase deposition (LPD) method. Alternatively, the ferrites were incorporated into an amorphous titanium dioxide matrix via a sol-­gel method which was used as a precursor for the hydrothermal synthesis of perovskite-­spinel nanocomposites. The nanocomposites were characterized by XRD, VSM, TEM, FE-­SEM, Raman, and PFM.

Abstract

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Perovskites (ATiO3 A=Ba or Pb) are ferroelectric (they exhibit electric polarization) and Spinels (CoFe2O4) are ferro or ferrimagnetic (they exhibit spontaneous magnetic dipoles) Magnetoelectric composites consist of a ferroelectric phase coupled together with a ferromagnetic phase

Introduction

Spinel Crystal Structure Perovskite Structure 3

Applying a stimulus to either phase can transfer a physical strain to the coupled phase and induce a response These materials have a range of applications in electronics and computers specifically in sensors, transistors, and data storage devices

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Cobalt Ferrite (Negative Magnetostriction Coefficient)

Lead Titanate (Electrostrictive Phase)

Polarization:

N S

5 dHdM

dMdP

dHdP

M E

0)0( PHP

PPHP 0)(

Methods

220°C 3hours

CoFe2O4

The CoFe2O4 (CFO) nanoparticles are synthesized by a hydrolysis reaction The DEG and NMDA act as both the solvent and as capping agents The hydroxide groups on the capping agents make the particles dispersible in polar solvents

Synthesis of Magnetic Nanoparticles CoCl2 20 + FeCl3 20 + DEG + NMDA

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Ti4+ Pb2+

H3BO3

Synthesis of Nanocomposites by LPD

1. 45 C, 3hrs

CoFe2O4

2. Annealed at 750 C 6hrs

PbTiO3-­CoFe2O4

MFn(n-­‐2m) + mH20 MOm + nF-­‐ +2mH+ (1) H3BO3 + 4HF BF4-­‐ + H3O+ + 2H2O (2)

LPD involves an equilibrium reaction Addition of Boric Acid shifts the equilibrium to the product side

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Integration of CFO into TiO2 matrix

EtOH CoFe2O4

Ti(butoxide)4

Adjusting the pH 3 to by HCl Adding molar amout of H2O dropwise

TiO2-­CoFe2O4 (powder)

Gelling Dry at 100 C for 3hrs

The CFO nanoparticles were integrated into amorphous TiO2 through a sol-­gel method

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The TiO2-­CFO powder was then used as seeds for the formation of PTO-­CFO nanocomposites under hydrothermal conditions ATiO3-­CoFe2O4

TiO2-­CoFe2O4 (powder)

A2+ + KOH + 15 mL H2O 180 C 12hrs (A = Ba or Pb)

Synthesis of PTO-­CFO by Hydrothermal Method

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X-­Ray Diffraction

20 30 40 50 60 700

50

100

150

200

250

300

Inte

nsity

(a.u

.)

2 (°)

PDF: 00-022-1086 CoFe2O

4

20 30 40 50 60 700

300

600

900

1200

1500

1800

2100

2400

CoFe2O

4PDF: 00-022-1086

PDF: 01-070-0747 PbTiO3

Inte

nsity

(a.u

.)

2 (o)

PTO-CFO hydrothermal

PTO-CFO LPD

CFO nanoparticles

The XRD pattern confirmed that the CFO nanoparticles were single phase. XRD patterns of the nanocomposites showed single tetragonal phase PTO. The CFO nanoparticles did not appear due to the weak intensity they exhibit in XRD.

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Magnetic Properties

-15000 -10000 -5000 0 5000 10000 15000-0.04

-0.02

0.00

0.02

0.04

Mom

ent (

emu/

g)

Field (Oe)

CFO nanoparticles

VSM measurements of the CFO nanoparticles.

-15000 -10000 -5000 0 5000 10000 15000-1.5x10-4

-1.0x10-4

-5.0x10-5

0.0

5.0x10-5

1.0x10-4

1.5x10-4

Field (Oe)M

omen

t (em

u)

PTO-CFO hydrothermally

PTO-CFO LPD

VSM measurements of PTO-­CFO nanocomposites.

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Morphology

TEM images of the CFO nanoparticles 12

TEM and FE-­SEM of PTO-­CFO nanocomposites formed by LPD.

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TEM and FE-­SEM of PTO-­CFO nanocomposites formed

hdyrdothermally 14

Magnetic Field Assisted Raman

800 700 600 500 400 300 2000

500

1000

1500

2000

Inte

nsity

(a.u

.)

Wavenumber (cm-1)

0 Oe 500 Oe 1000 Oe 1500 Oe 2000 Oe

A1g

A1(3

TO)

Si

B1+E

E(2

TO)

Spinel modesPerovskite modes

Raman Bands Ferrite Perovskite

Field (Oe) A1g A1(3TO) B1+E E(2TO) Si 0 713.5 584.2 290.3 207.1 525.2

500 677.3 574.8 291.9 199.4 525.3 1000 675.0 571.3 290.1 198.8 525.4 1500 684.0 566.5 287.1 197.7 525.4 2000 691.4 565.2 283.4 195.2 525.4

Raman Spectra of PTO-­CFO powder prepared by LPD placed on a silicon wafer. Shifts in the perovskite

modes suggest a coupling between the magnetic and

piezoelectric phases.

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800 700 600 500 400 300 2000

1000

2000

3000

4000

5000

In

tens

ity (a

.u.)

Raman Shift (cm-1)

0 Oe 500 Oe 1000 Oe 1500 Oe 2000 Oe

Si

A1g

A1(3

TO)

B1+E

E(2

TO)Spinel modes

Perovskite modes

Raman Bands Ferrite Perovskite

Field (Oe) A1g A1(3TO) B1+E E(2TO) Si 0 709.8 577.7 289.4 199.7 508.3

500 710.8 579.6 289.4 199.7 508.3 1000 709.8 580.6 290.4 201.7 508.3 1500 710.8 578.7 290.4 200.7 508.3 2000 710.8 580.6 290.4 201.7 508.3

Raman Spectra of PTO-­CFO powder

prepared hydrothermally

placed on a silicon wafer. Shifts in the perovskite modes suggest a coupling

between the magnetic and

piezoelectric phase.

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Magnetic Field Assisted Piezoresponse Force Microscopy

-20 -10 0 10 20

0.0

1.0x10-10

2.0x10-10

3.0x10-10

4.0x10-10

5.0x10-10

6.0x10-10

Am

plitu

de (m

)

Voltage (V)

0 Oe 500 Oe 1000 Oe 1500 Oe 2000 Oe

-20 -10 0 10 20

-100

-50

0

50

100

150

200

250

300

Pha

se (°

)Voltage (V)

0 Oe 500 Oe 1000 Oe 1500 Oe 2000 Oe

PFM measurements of PTO-­CFO nanocomposites synthesized by LPD method.

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References

Yourdkhani, A.;; Perez, A.;; Lin, C.;; Caruntu, G. Chem. Mater. 2010, 22, 6075 6084 6075. Caruntu, D,;; Caruntu, G,;; Chen, Y.;; C.;; Goloverda, G.;;

Kolesnichenko, V. Chem. Mater. 2004, 16, 5527-­5534. Liu, A.;; Zhang, X.;; Xu, Y.;; Niu , X.;; Zheng, X.;; Ding, X. Chemosphere

59, 2005, 1367 1371. Wang, Y.;; Xu, H.;; Wang, X.;; Zhang, X.;; Jia, H.;; Zhang, L.;; Qiu, J.;; J.

Phys. Chem. B 2006, 110, 13835-­13840.

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Acknowledgements

This works was sponsored by Louisiana Board of Regents/National Science Foundation NSF(2010-­15)-­RII-­UNO Thanks also goes to Dr. Daniela Caruntu for her help in the CFO nanoparticle synthesis and to Denny Lenormand for help with the VSM measurements.

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