Study Of Doped Cr2O3 Nanoparticles

By:Gaurav Kumar Yogesh

Reg. No. CUPB/M.Sc./SBAS/PMS/2013-14/01

Supervisor: Dr. Kamlesh Yadav

(Assistant Professor)

Centre for Physical and Mathematical Sciences

Central University of Punjab, Bathinda

Introduction

Nanomaterials

Historic background

Classification of nanoparticles

Method to approach nanoparticle

Properties and application

Gap analysis

Objective

Microwave assisted Synthesis

Observations to be recorded

Time Schedule for M.Sc. Dissertation

References

Nanomaterials have dimensions of less than 100 nm and atleast 1 nm.

They have superior properties than bulk.

There are various methods for the synthesis of nanomaterials like sol gel, microwave

synthesis etc.

They can generally be classified as one of two types: engineered or non-engineered

Engineered nanoparticles are intentionally designed and created with physical properties

tailored to meet the needs of specific applications.

Non-engineered nanoparticles are unintentionally generated or naturally produced, such as

atmospheric nanoparticles created during combustions.

Historical evidences of use nanoparticles

The Lycurgus cup is from the 4th century AD and was

probably carved in Rome. It appears RED by reflexion and

GREEN by transmission. This technology has been used

during the roman era. Gold and silver were added to glasses.

Fig. http://www.cambridge2000.com/gallery

Size effects constitute a peculiar and fascinating aspect of nanomaterials. The effects determined by sizepertain to the evolution of structural, thermodynamic, electronic, spectroscopic, electromagnetic andchemical features of these finite systems with changing size.

Example: gold nanoparticle.face

LS-FCM University of Bologna

Top down approach Down up approach

1. Commonly found as the rare minerals Eskolaite, Cr2O3

2. It has rhombohedral structure

3. There are two descriptions of the rhombohedral lattice system.

Hexagonal axes: The unit cell is a = b ≠ c; α = β = 90°, γ = 120°

Rhombohedral axes: This is a primitive unit cell with parameters

a = b = c; α = β = γ ≠ 90°.

Fig. Rhombohedral cell

1.Magnetic properties

Cr2O3 nanoparticle is an antiferromagnet with a Neel temperature TN of 311 K .

Find diverse technological applications in information storage and spintronics.

Surface spins increases as the particle size is decreased.

2. Electrical properties

Cr2O3 is intrinsic semiconductor Whose conductance is independent of oxygen partial pressure at

high temperature (>1273 K).

At lower temperature the oxide is an extrinsic p-type.

Due to the presence of a small amount of unoccupied cr4+ states in the bulk which hope from one

lattice chromium to next at temperature above 623 K.

3. Structural properties

Rhombohedral structure of the material with lattice parameter, a = b= 4.953 Å; c = 13.578 Å,

Optical properties arise due to surface Plasmon resonance.

SPR is caused due to the coherent motion of the C.B electrons from one surface of the particle to the

other, upon interaction on electromagnetic radiation.

Decrease in size below the electron mean free path gives rise to the intense absorption of UV- visible

radiation.

Optical excitation of the SPR gives rise to the surface plasmon absorption.

Surface plasmon absorption depends on the size and the shape of the particles.

Solar energy thermal collector

Insulating antiferromagnetic material

Tunnel junction barrier

Coating for the passivation of the surface against corrosion

Microelectronics

Sensors

Piezoelectric devices

Coating materials for thermal protection hydrogen storage antimicrobial and antibacterial

activity

Green pigments

Synthesis with a sol method by using capping agents to prevent aggregation and control the

size.

Quantum confinement occurs when the electrons motion is limited by the size of the NP.

The electronic energy levels of the particle around the Fermi level are affected only for very

small sizes.

The UV-visible absorption is determined by the surface plasmon resonance, which is size

and shape dependent.

Exhibit a very weak luminescence.

Show valuable catalytic properties, owing to the large surface to mass ratio.

There are various ways of preparing nanoparticles:

1. Sol-gel method

2. Microwave synthesis

3. Hydrothermal reaction

4. Arc discharge reaction

For our experiment we use the sol-gel and microwave synthesis methods

Microwaves radiation are a form of electromagnetic energy with frequencies in the range

of 300 MHz to 300 GHz.

Interactions between materials and microwaves are based on two specific mechanisms:

dipole interactions and ionic conduction.

In the Dipole interactions the polar ends of a molecule tend to re-orientate themselves and

oscillate in step with the oscillating electrical field of the microwaves. Heat is generated

by molecular collision and friction.

Jimmy. C.Yu.,2004

Dipolar oscillation Ionic conduction

Molecular Orientation = Molecular Friction = Heat

Conductive heat

Heating by convection currents

Slow and energy inefficient process

Broad dynamic temperature range up to 300K

Microwave energy can heat the whole sample volume very effectively.

It yields better product in short duration.

Thermal equilibrium is quickly achieved.

The microwave synthesized products were calcined in air to obtain the well-defined crystallographic

phase.

Low energy is required.

Higher chemical yield is obtained.

Microwave synthesis apparatus can be turned off instantly when the reaction mixture reaches the

temperature set point.

Parameters can be controlled excellently.

Safety is the most important feature.

Cr2O3 nanoparticles prepared by microwave synthesis and sol gel method is advantageous to

our study as it is time saving and a good morphology can be achieved with the help of this. So

our present study is based on the formation of nanoparticles. The structural, magnetic and

electrical properties will be strongly influenced by the doping of the several element of d block

element such as Fe, ZnO and Co. From the literature survey done so far, very few literature is

available on the synthesis of Cr2O3 nanoparticles by using microwave synthesis method and sol-

gel method.

The lattice parameters will be calculated using the plot of X-Ray diffraction.

We can calculate the variation of intensity with the angle of diffraction.

Surface morphology can be calculated using SEM.

Electrical band can be calculated by FTIR

The lattice parameters like a, b, c and α, β, γ will be calculated by using x-ray diffraction, also

the graph between intensity and 2θ will be helpful for estimating the variation of intensity with

2θ. The crystallite size can be calculated by using the Debye scherrer’s formula D=

0.9λ/βcosθ, where D is crystallite size, is wavelength of x-rays, is full width at half maximum

and θ is Bragg’s angle.

To synthesize the Cr2O3 nanoparticles by using microwave synthesis method and sol gel

method then study the doping effect on the optical, electrical and structural properties of

nanoparticles.

Location of Research

We will prepare Cr2O3 nanoparticles by Microwave synthesis and by using Sol-gel technique at

Central University of Punjab. For the characterization of the prepared nanoparticles we have to go

suitable places if university permits.

23

As Cr2O3 nanoparticles will be synthesized by microwave assisted synthesis and it is

expected that there will be a change in the properties compared to the bulk.

The Electrical, Structural, Optical will be correlated.

Sr. No. Activities January February March April May

1 Literature survey

2 Experimental work

3 Characterisation

4 Draft submission

5 Final submission

References

Abdullah, M. M., Rajab, F. M., and Al-Abbas, S. M. (2014). Structural and optical characterization of Cr2O3

nanostructures: Evaluation of its dielectric properties. AIP Advances, 4(2), 027121.

Balouria, Vishal; Singh, A.; Debnath, A. K.; Mahajan, Aman; Bedi, R. K.; Aswal, D. K.; Gupta, S. K., Synthesis

and characterization of sol-gel derived Cr2O3 nanoparticles.

F. Farzaneh and M. Najafi, Synthesis and Characterization of Cr2O3 Nanoparticles with Triethanolamine in Water

under Microwave Irradiation, Received: 17 May 2011 / Revised: 9 January 2012 / Accepted: 15 January 2012

Hung, C. H., Shih, P. H., Wu, F. Y., Li, W. H., Wu, S. Y., Chan, T. S., & Sheu, H. S. (2010). Spin-phonon coupling

effects in antiferromagnetic Cr2O3 nanoparticles. Journal of nanoscience and nanotechnology, 10(7), 4596-4601.

Mohanapandian and Krishnan.,2014 study Effect of Concentration of Ni2+ on the Physio Chemical Properties of

Cr2o3 Nanoparticles

Pei, Z., and Zhang, Y. (2008). A novel method to prepare Cr2O3 nanoparticles.Materials Letters, 62(3), 504-506.

Pei, Z., Xu, H., and Zhang, Y. (2009). Preparation of Cr2O3 nanoparticles via C2H5OH hydrothermal

reduction. Journal of Alloys and Compounds, 468(1), L5-L8.

Zhang, W. S., Bruck, E., Zhang, Z. D., Tegus, O., Li, W. F., Si, P. Z. & Buschow, K. H. J. (2005). Structure and

magnetic properties of Cr nanoparticles and Cr2O3 nanoparticles. Physica B: Condensed Matter,358(1), 332-338.