Fabrication And Characterization Of Bismuth Ferrite Nanofibers By

Electrospinning Method

Under the guidance of Dr. S. Balakumar

Presented by M. HAKKEEM

Register No. 34211007National Centre for Nanoscience and Nanotechnology

University of MadrasGuindy Campus

Chennai – 600 025.

Outline Multiferroics – definition

Bismuth ferrite

Existing challenges with the material

Scope of the thesis

Experiment design

Synthesis

Result and discussion…..

Multiferroics – Definition

Multiferroics are single phase materials which simultaneously possess two or more primary ferroic properties.

Ferromagetic (anti-)

Ferroelectric

Ferroelastic

Ferrotoroidic

Bismath Ferrite Rhombohedral distorted

perovskite structure

Room temperature Magnetoelectric effect

Antiferromagnetic (Tn)= 643 K

Ferroelectric (Tc) = 1103 K

In homogenous spin structure

Application of BiFeO3

Transducers , Magnetic field sensors and information storage in industry .

The data can be written electrically and read magnetically.

The best aspect of ferroelectric random access memory (Fe RAM)

BiFeO3 potential application of spintronics and photo catalytic compound ……

Existing challenges with the

material at microscale High leakage current

Small remnant polarization

High coercive field

Ferroelectric reliability

Inhomogeneous magnetic spin structure

Goals at the Nanoscale…

Reduce the leakage current

Reduce the impurity phases

Reduce the oxygen vacancy

Suppress the inhomogeneous spin structure

Increase the values of Ps, Pr and Mr

Scope of the thesis Controlling the size of the particles in

nanoscale

Controlling dimensionalities of the material (particles, thinfilms, nanofibers, etc.)

Doping or substitution

Materials and methods Overview of the method :

BiFeO3 Nanofiber were fabricated in sol – gel based electrospinning method

The process of fabricating the electrospinning solution involved the sol gel method while the fabrication of naofibers involved the electrospinning method.

Further the process of annealing yielded the BFO phase nanofibers

Materials Metal precursors :

Bismuth (III) nitrate pentahydrate [Bi (NOᴣ)ᴣ.5H2O]

Iron (III) nitrate nonahydrate [Fe (NO ᴣ)ᴣ.9H2O]

Polyvinylpyrrolidone [(C6H9NO)n]

Solvent :

Glacial acetic acid [C2H4O2]

Double distilled water [DD H2O]

Experiment designS. No. Parameters Value

1 Distance between needle stage and collector 10 cm

2 Applied voltage 8, 10, 15 & 20 kV

3 Collector Plate type

4 Processing duration 6 hrs

5 Syringe capacity 2 ml

6 Flow rate 0.2 ml per hrs.

Synthesis flow chart

Result and discussion We have fabricated bismuth ferrite

(BiFeO3/BFO) nanofibers by electrospinning method.

The applied voltage is found to be a potential parameter in determining the diameter and mechanical property of the nanofibres.

Therefore we have fabricated BFO nanofibers by varying the applied voltage at 8 kV, 10 kV, 15 kV and 20 kV.

Continues . . . All the fabricated nanofibers were annealed at 450oC

for 2 hrs in order to form the BFO phase.

The fabricated nanofibers were characterized for their

Crystalline phase and structural property by XRD

Morphological property by SEM , HRTEM

Optical property by UV-Visible-DRS technique

Material phase formation by TGA.

Thermogravimetric analysis(TGA)

The weight loss material &solvent.

150 and 200 oC pvp evaporation

200 and 400 oC acetic acid solvent evaporation

450 and 1000 oC there were no residual elements to be evaporated.

10 kV-450oC

XRAY – Diffraction (XRD) Crystalline

phase and structural analysis

BFO nanofibers annealed at 450 and 550oC for 2 hrs.

550oC - secondary phases -as Bi2Fe4O9 and Fe2O3 were formed

450oC – no secondary and impurity phases

10 kV

10 kV

Continues . . . All the fabricated

nanofibers at 8, 15 and 20 kV were annealed at 450 oC for 2 hrs

All the other BFO samples contained the secondary phases (Bi2O3)

Then fabricated nanofibers at 10 kv Were controlled mechanism has to be Found out in order to fabricate the secondary phase free BFO nanofibers

Energy dispersive spectroscopy (EDS)

Compositional analysis

The graphs confirmed that All the elements such as Bi , Fe O of BFO compound

Scanning electron microscope (SEM)

(a) 8 kv it ‘s not sufficient Small diameter

(b) 10 kv large

diameter ,Poor mechanical strength.

(c) 15 kv excellent fiber, homogenous Size distribution, diameter of size 50-100 nm

(d) 20 kv very small length, were fibers are broken relatively inhomogenous.

High Resolution Transmission

Electron Microscope (HRTEM)

UV - DRS Optical studies

The diffuse reflectance peaks between 700 - 800 nm and 600 – 550 nm regions

optical property of the nanofiber prepared at 20 kV was significantly influenced .

The perhaps due to the well pronounced secondary peak Bi2O3

Continues . . .The change of band gap value of BFO nanofibers with respect to the applied voltage

S. No. Material Band gap (eV)

1BFO NF @ 8 Kv

2.47

2BFO NF @ 10 kV

2.42

3BFO NF @ 15 kV

2.45

4BFO NF @ 20 kV

2.44

Summary and conclusion Bismuth ferrite (BiFeO3) nanofibers were

fabricated by electrospinning method by varying the applied voltages 8 kV, 10 kV, 15 kV and 20 kV.

The minimum voltage of 8 kV where the nanofiber formation was occurred considered as the threshold energy

All the fabricated nanofibers were annealed at 450 oC for 2 hrs.

all the nanofibers were characterized for the XRD, EDS, SEM , HRTEM , UV-DRS technique .

Continues . . . From the XRD results, it was found that the

phase pure BFO was obtained for the nanofiber which fabricated at 10 kV.

The other nanofibers fabricated at 8, 15, and 20 kV were found to with secondary phase such as Bi2O3, Bi2Fe4O9.

Continues . . . The compositional analysis revealed that all the

samples did contain the element of bismuth ferrite composition with rational percentage.

From the microscopy graphs (SEM and HRTEM), it was found that all the BFO were possessed fiber morphology.

However, the fiber fabricated at 8 kV was found to

be aggregated structure.

Continues . . . On the other hand, the fibers fabricated at 10 and

20 kV were found to be broken structure

A well aligned and homogeneous size distributed nanofibers were found in the samples which fabricated at 15 kV.

Therefore, for the study it was evident that the overall qualities of the nanofibers in terms of their morphology, mechanical, size distribution of were processing applied voltage dependent.

Thanking to all