Synthesis AND Characterization of barium titanate and cobalt ferrite powders for preparation of magneto electric composites

A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

Bachelor of Technology in Ceramic Engineering

BY

Sahil singlaRoll no. 10508029

DEPARTMENT OF Ceramic ENGINEERINGNATIONAL INSTITUTE OF TECHNOLOGY

ROURKELA-769008

1

Synthesis AND Characterization of barium titanate and cobalt ferrite powders for preparation of magneto electric composites

A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

Bachelor of Technology in Ceramic Engineering

BY

Sahil singlaRoll no. 10508029

Under Guidance Of

Prof. Arun Chowdhury

DEPARTMENT OF Ceramic ENGINEERINGNATIONAL INSTITUTE OF TECHNOLOGY

ROURKELA-769008

2

NATIONAL INSTITUTE OF TECHNOLOGYROURKELA

2009

CERTIFICATE

This is to certify that the thesis entitled, “Synthesis and Characterization of

barium titanate and cobalt ferrite powders for preparation of magnetoelectric

composites” submitted by Mr. Sahil Singla in partial fulfillment of the

requirements of the award of Bachelor of Technology Degree in Ceramic

Engineering at the National Institute of Technology, Rourkela is an authentic work

carried out by him under my supervision and guidance.

To the best of my knowledge, the matter embodied in the thesis has not been

submitted to any other university / institute for the award of any Degree or

Diploma.

Date: 12.05.2009 Prof. Arun Chowdhury

Dept. of Ceramic Engineering

National Institute of Technology Rourkela – 769008

3

ACKNOWLEDGEMENT

It gives me immense pleasure to express my deep sense of gratitude to my supervisor

Prof. Arun Chowdhury for his invaluable guidance, motivation, constant inspiration

and above all his ever co-operating attitude enabled me in bringing up this thesis in

present elegant form.

I am extremely thankful to Prof. S. Bhattacharayya Head, Department of Ceramic

Engineering and the faculty members of Ceramic Engineering Department for providing

all kinds of possible help and advice during the course of this work.

It is a great pleasure for me to acknowledge and express my gratitude to my parents for

their understanding, unstinted support and endless encouragement during my study.

I am greatly thankful to all the staff members of the department and all my well wishers,

class mates and friends for their inspiration and help.

Lastly I sincerely thank to all those who have directly or indirectly helped for the work

reported herein.

SAHIL SINGLA

ROLL NO: 10508029Department of Ceramic Engineering

National Institute of Technology, Rourkela

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ABSTRACT

Both Conventional method and auto combustion methods were followed to synthesize powders

of Barium titanate and Cobalt ferrite. Nowadays auto combustion synthesis has attracted much

more attention due to the inexpensive precursors and ease of batch calculations. Unagglomerated

fine powders can be obtained by auto combustion method. During preparation of BaTiO3 and

CoFe2O4 by dry route they were calcined at 800o C for two hours and 1000o C for one hour

respectively. Powders of Barium Titanate and Cobalt Ferrite synthesized by Auto combustion

method were calcined at 1000o C for one hour and 1000o C for two hours respectively. Phases of

particular compounds have been confirmed by XRD. For preparing multi ferroic composites the

two separate powders are proved to be suitable.

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ContentsSerial No. Pages

1) Chapter 1: Introduction 4

2) Chapter 2: Literature Review 9

3) Chapter 3 : Experimental Procedure

3.1: Preparation of TiO(NO3)2 solution 12

3.2: Preparation of BaTiO3 Powder 12

3.3: Preparation Of Cobalt Ferrite Powder 15

4) Chapter 4: Results and discussions 18

5) Chapter 5: Conclusions 22

6) Chapter 6: References 23

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Chapter 1:

INTRODUCTIONWith the development of electronic technology, composite materials have been widely used for

electronic devices where higher densities, limited space and multifunction are required. Recently

the ferroelectric–ferromagnetic composite materials were intensively researched for two uses: the

magnetic–electric sensors in radio-electronics, optoelectronics, microwave electronics and

transducers and the compact electrical filters for suppressing electromagnetic interference

(EMI). As for the magnetic–electric sensors, high ferroelectric content was necessary for the

composite materials with sufficient resistivity to generate magnetoelectric effect.

Magneto electric coupling describes the influence of a magnetic field (or an electric field) on the

polarization (or magnetization) of a material.

In the past few years, extensive research has been conducted on magneto electric effect in single

phase and composite materials. Direct polarization of a material under a magnetic field or an in

induced magnetization under an electric field requires the simultaneous presence of long range

ordering of magnetic moments and electric dipoles.

Magneto Electric materials are of two types:

Single Phase

Composites

In a magnetoelectric (ME) composite the magnetostrictive strain in the magnetic phase creates an

electric polarization in the adjacent piezoelectric phase and hence is capable of converting

magnetic field into electric field and vice versa. Such product property can be utilized in smart

materials used in sensors, processors and feedback systems.

The first magneto electric effect was predicted in Cr2O3, but magneto electric materials with a

single phase show a weak magneto electric effect , hence the need of composites.

Magneto electric composites on other hand have large magneto electric coefficients of magnitude

of magneto electric voltage coefficients. The composites are made exploiting the product

property of materials.

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Composite materials are engineered materials made from two or more constituent materials with

significantly different physical or chemical properties and which remain separate and distinct on

a macrospace level within the finished structure.

Multi ferroic materials exhibit more than one primary ferroic order parameter such as

ferro/antiferromagnetism, ferroelectricity, ferro elasticity in a single phase.

There are number of physical methods for preparing nano crystalline materials viz inert gas

condensation, physical vapour deposition , laser ablatiion, chemical vapour deposition,

sputtering, molecular beam epitoxy etc. Among the available solution- chemistryroutes,

combustion technique is capable of producing nano crystallline powders of oxide ceramics, at a

lower calcination temperature in a surprisingly short time. The solution combustion is a two step

process:

Formation of a precursor

Auto ignition

The formation of precursor (viscous liquid or gel), is a primary condition for an intimate

blending of the starting constituents and preventing the random redox reaction between a fuel

and an oxidizer. The very high exothermicity generated during combustion manifests in the form

of either a flame or a fire and hence the process is termed as auto ignition process. The nature of

the fuel and its amount are some of important process parameters for getting the transparent

viscous gel without any phase seperation and precipitation. Thus the basic characterstics of a fuel

are that it should be able to maintain the compositional homogenity among the constituents also

undergo combustion with an oxidizer at low ignition temperature. Commonly used fuels are

glycine, urea, citric acid etc.

Sintered composite materials are much easier as well as cheaper to prepare than unidirectional

solidified in situ composites. As regard to the ME effect it was found that ME composites made

by unidirectional solidification always gave a higher value than those prepared by solid state

sintering of the presintered component phases for a given composition.

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Nanocrystalline CoFe2O4 samples can be synthesized by following methods; coprecipitation,

combustion, citrate gel and conventional ceramic method. AR grade metal nitrates,

Co(NO3)2·6H2O and Fe(NO3)3·9H2O were used for all three syntheses.

Nanocrystalline BaTiO3 samples can be synthesized by autocombustion, solid oxide route and

conventional ceramic method.

Recently auto combustion synthesis method attracted considerable attention in fabricating

homogeneous and unagglomerated fine ceramic powder. Availability of comparatively

inexpensive precursors, simple calculations, eases in optimizations of process parameters proved

to be advantageous in auto combustion synthesis.

Other Magnetoelectric Applications:

SENSORS

Magnetoelectric Sensor

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TRANSDUCERS

Magnetoelectric Transducer

MICROWAVE DEVICES1. RESONATOR

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2. PHASE SHIFTER

3. OSCILLATOR

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Chapter 2:

LITERATURE REVIEWHistorically BaTiO3- CoFe2O4 composites were first obtained in 1972 by Van Suchtelen.

Type of materials that undergo ME multiferroic: Single material/ Composite

Theoretically the magneto electric effect came into picture in 1894 when curie discussed

correlation of magnetic and electric properties in low symmetry crystals.Another strong footing

on ME effect theoretically is by L.D. Landau in 1957. According to him, “ The magneto electric

effect is odd with respect to time reversal and vanishes in materials without magnetic structure.

First experimental observation of the ME effect was in 1960 by Astrov who found the electric

field induced magneto electric effect in Cr2O3. One year later the reverse effect in same system

was observed by Rado et al.The BaTiO3- CoFe2O4 composite was first prepared by unidirectional

solidification of BaTiO3- CoFe2O4 eutectic liquid. Van Suchtelan was the pioneer and he

introduced the product properties.Among various magneto electric composite systems, BaTiO3 /

CoFe2O4 composite materials are first investigated. the unidirectional solidification lets the

composite to come up with a lamellar morphology. The phases as Co2TiO4 and (BaFe12O9)y

(BaCo6Ti6O19)1-y could also exist in the system. The resulting lamellar microstructure prevents

the relatively conductive CoFe2O4 phase from forming conducting chains along the poling

directions. Consequently the composite materials posses a relatively high ME sensitivity (30

mV/cm-Oe) but the unidirectional solidification process is not easy to be implemented. Solid

state reaction or conventional ceramics method is usually followed to prepare BaTiO3- CoFe2O4

or BaTiO3- CoFe2O4 based composites. The advantages of this route are: simple, cheap and free

choice of composition of the constituents. Using this method various composites have been made

such as CoFe2O4/PZT, Ni0.75Co0.25Fe2O4 + Ba0.8Pb0.2TiO3 etc.Among these different composites

BaTiO3-CoFe2O4 composite seems to be most promising for applications. We therefore put the

effort to study that system. Multiferroic BaTiO3-CoFe2O4 composite could be regarded as model

system illustrating magneto electric effect. BaTiO3 is a typical ferroelectric material which has a

large piezoelectricity. CoFe2O4 is ferromagnetic with large magnetization. Wet chemical

methods are coming into this field of particulate composite with a lot of advantages. Firstly the

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sintering temperature likely to be reduced as that is followed in conventional ceramic method.

This will save electrical energy in processing. Playing with the properties with varrying

compositions is also possible. Composite properties could be improved by proper mixing of

constituents. Wet chemical method is very much helpful.

As a summary of some of the literatures which came across is tabulated as follows:

TABLE 1:

Serial no. Name/group Route followed to Synthesize CoFe2O4

Conclusions

1 S.D. Bhame, P.A. Joy Conventional ceramic method, Combustion method, Citrate method, Coprecipitation method and

Lowest average grain size and highest magnetostriction is obtained for the materialsynthesized by an autocombustion method

2 R.W. McCallum, K.W. Dennis, D.C. Jiles, J.E. Snyder, Y.H. Chen

Auto Combustion method

High values of the strains at low field strengths along with enhanced magneto mechanicalcoupling factor have been identified.

3 A. Goldman, T. Nakamura

Auto Combustion method

Exhibit improved magnetic permeability which depends on the microstructure, density,porosity, grain size.

Table 1: Previous works on synthesis of CoFe2O4

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TABLE 2:

Serial no. Name/group Route followed to Synthesize BaTiO3

Conclusions

1 A. Ianculescu, D. Berger, C. Matei, L. Mitoşeriu, E. Vasile

Citrate Gel Method BaTiO3 nano powders present various structural and morphological features depending on the type of raw materials

2 Sung-Soo Ryu , Sang-Kyun Lee , Dang-Hyok Yoon

Solid State Reaction Method

Reaction Temperature was decreased by doping Calcium

3 U.Manzoor, D.K.Kim Solid State Reaction Method

Enhanced Reaction Rates due to increase in Contact area due to Small particles

Table 2: Previous works on synthesis of BaTiO3

Chapter 3:

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Experimental ProcedureThere are two types of routes for synthesis of powder namely Auto Combustion method and Dry

route. For the preparation of Barium Titanate, the precursors required are: TiO(NO3)2 solution,

Barium Nitrate, Ammonium Nitrate, Citric acid, EDTA.

3.1 Preparation of TiO(NO3)2 solution:

Required amount of ammonium sulphate, TiO2 were mixed with concentrated H2SO4. Then

solution was heated and undergone continuous stirring until yellowish transparent solution was

obtained. It was left without disturbance for about 3 hours to get cold. Then equal volume of

distilled water was taken and solution was slowly mixed with it. Care was taken during this step

to ensure that temperature of the solution was below 10o C (ice bath was used). Then NH4OH

was added to diluted solution till pH of 9 was reached. A white precipitate was obtained which

was of titanyl hydroxide (TiO(OH)2) . This Precipitate was obtained by centrifuging. In

centrifuging process speed was slowly increased to 9100 rpm and slowly decreased. This was

done to remove dissolved SO2, NO2 and extra distilled water present. Ammonia is removed by

decantation. Centrifuge was done for about 3 times. Concentrated HNO3 acid was diluted in 60

ml of distilled water to get 1:1 ratio. After dilution precipitate was added and dissolved which

gave titanium oxy nitrate solution. Temperature was maintained about 10oC during dilution of

concentrated HNO3 acid.

3.2 Preparation of BaTiO3 Powder:

3.2.1 Dry Route:

BaTiO3 was prepared by the solid oxide route in which BaCO3 and TiO2 was taken in 1:1

mole ratio and it was ground in the mortar for about 1 and a ½ hrs with isopropyl alcohol as

the grinding medium. Then the powder was calcined at 800oC for 2 hrs and XRD was done to

determine its phase.

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Flowchart For Preparation Of BaTiO3 Powder By Dry route

3.2.2 Auto combustion method:

Ba(NO3)2 powder was taken and dissolved in distilled water. Then it was placed on hot plate

for about fifteen minutes and with little stirring Ba(NO3)2 solution was obtained. Then same

molar ratio of TiO(NO3)2 solution was taken and added to barium nitrate solution. Then to it

Citric acid, Ammonium nitrate and EDTA were added in molar ratio of 1.5, 12 and 0.1

respectively. Here Citric Acid acts as fuel. Then it was set for combustion. On combustion

gases were evolved generally consisting of H2O, NO2 or basically NO. First it transformed to

solution then the gel which appeared comparatively viscous. The gel automatically

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BaCO3 TiO2

BaCO3 + TiO2

Grinding Grinding Media

Powder

Calcination

BaTiO3 Powder

underwent combustion and barium titanate was obtained. Then it was calcined at 1000oC for

an hour.

Flow Chart for Preparation of BaTiO3 powder by Autocombustion Method

3.3 Preparation Of Cobalt Ferrite Powder:

3.3.1 Dry Route:

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Ba(NO3)2 Soluton

TiO(NO3)2 Solution

Ba(NO3)2 + TiO(NO3)2

Solution

Citric Acid + NH4NO3 + EDTA

Auto Combustion

Foam Like Material

Grounded

White Coloured Powder

Calcined

BaTiO3 Powder

Co3O4 Powder Fe2O3 Powder

Gel

Flowchart for preparation of Cobalt Ferrite Powder By Dry Route

CoFe2O4 was also prepared by the solid oxide route in which Co3O4 and Fe2O3 were taken in 1:3

mole ratio and both were mixed and grounded for about 1 & ½ hrs with acetone as the grinding

media. The powder was then calcined at 10000C/1 Hour and its XRD was done to determine its

phase.

3.2.2 Auto combustion method

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Cobalt Nitrate Solution Iron Nitrate Solution Citric Acid

Grinded Grinding Media

Powder

Calcination

CoFe2O4 Powder

Flowchart for preparation of Cobalt ferrite powder by Autocombustion Method

For preparation of cobalt ferrite by auto combustion route precursors Cobalt nitrate solution, Iron

nitrate solution and Citric acid in molar ratio of 1:2:3 were taken. For this Iron nitrate solution

was prepared by dissolving Iron nitrate in distilled water and then strength was measured. Also

strength was measured for cobalt nitrate solution. Then the precurssors were mixed in the above

ratio. Then pH was made 7 by addition of NH4OH. Then auto combustion was performed.

Magnetic stirrer was placed in the beaker and it was kept on the hot plate which took around 2

hours. After that a fluffy black mass is obtained which was grounded to powder. And then XRD

was performed. After that it was calcined at 1000oC for 2 hours.

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pH= 7 Ammonium Hydroxide

Auto Combustion

Foam like Material

Grinded

Calcination

Cobalt Ferrite Powder

Chapter 4:

Results and discussionsAfter calcination the samples were characterized by XRD.

4.1 XRD Results of Barium Titanate

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Fig 1: XRD graph of BaTiO3 prepared by auto combustion method (pH not adjusted)

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Fig 2: XRD graph of BaTiO3 prepared by auto combustion method (pH= 5-7)

Following results have been observed for two samples one with no pH adjustment and other with

pH from 5 to 7 as depicted in figures 1 and 2:

For both samples the XRD peaks were found to be matched with reference sample 75-0461. It

was also confirmed that cubic Barium Titanate was formed after calcination. It belongs to the

space group Pm-3m. Lattice parameter was observed as 4.0119 Ao .

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4.2 XRD Results Of Cobalt Ferrite

Fig 3: XRD graph of CoFe2O4 synthesized by solid state method

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Fig 4 : XRD graph of CoFe2O4 synthesized by auto combustion method

Both the samples obtained from Solid reaction as well as Auto combustion method were

compared on the basis of XRD analysis as depicted in figures 3 and 4.

For both the samples the XRD peaks were found to be well matched with the reference sample

88-2152. Lattice parameter is same for both the samples equal to 8.396 Ao.

From the patterns of the XRD it is observed that the CoFe2O4 obtained from Auto combustion

route has broad peaks as compared to that obtained by solid reaction route.

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Chapter 5:

Conclusions Cubic barium Titanate was obtained after calcinations at 800oC for 2 hours.

Further calcination of samples at higher temperature is required in order to get tetragonal

phase which is desired phase.

Cubic Cobalt ferrite (spinel) phases were confirmed in XRD results after calcinations at

1000o C for two hours.

The difference in broadening of corresponding peaks of the two different samples

suggests that crystal size obtained by auto combustion method are finer.

From auto combustion method finer particles are obtained though further details are

required to conclude the optimum calcinations temperature.

As the phases have been confirmed by XRD these samples can be used for preparation of

magnetoelectric composite.

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Chapter 6:

References

1. Goldman, Modern Ferrite Technology, Van Nostrand Reinhold, New York, 1990.

2. T. Nakamura, J. Magn. Magn. Mater. 168 (1997) 285

3. R.W. McCallum, K.W. Dennis, D.C. Jiles, J.E. Snyder, Y.H. Chen, Low Temp. Phys. 27

(2001) 266.

4. . D.H. Yoon, B.I. Lee, J. Ceram Process. Res. 3(2), 41 (2002).

5. J. Ryu, S. Priya, K. Uchino, H.E. Kim, D. Viehland, J. Korean Ceram. Soc. 39 (9) (2002)

813–817.

6. Multiferroic and magnetoelectric materials, W. Eerenstein, N. D. Mathur & J. F. Scott

2006.

7. U.Manzoor and D.K.Kim: Scripta Mater., 2006, 54, 807.

8. A. Ianculescu, D. Berger, M. Viviani, C.E. Ciomaga, L. Mitoşeriu, E. Vasile, N. Drăgan,

D. Crişan, J. Eur. Ceram. Soc., 27, 3655 (2007)

9. Structural analysis and electrical properties of ME composites, S.A. Lokare, R.S. Devan,

B.K. Chougule, 2007

10. The physics of magnetoelectric composites R. Gro¨ ssingera,_, Giap V. Duongb, R. Sato-

Turtellia, 2007

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