Mangan - Zinc Ferrite

Material Preparation

Weighing

Wet Mixing

Binder addtion

Sintering

Evaluation

Pressing

XRD, SEM, Physical &

Magnetic properties

1100 oC, 1200

oC, 1300

oC

1hr, 2hr, 3hr

30MPa

3% PVA, 5%PEG

Drying of starting materials

MnO, ZnO, Fe2O3

Abstract—Ceramic ferrites are magnetic materials composed of

selected oxides with iron oxides. The most common commercial soft

magnetic materials are spinel ferrites, Mn-Zn and Ni-Zn ferrites

having general structure AB2O4. The Manganese-Zinc ferrite is

preferred for lower frequency applications less than 2 MHz where as

Ni-Zn ferrite is preferred for higher frequency applications generally

for power transformers, power inductors and general power

applications. The microstructure and properties of ceramic ferrites

depend critically upon the processing conditions.

The physical properties and sintering characteristics of (Mn(1-

x)Znx)Fe2O4 have been carried out for equimolar composition, x =

0.5, at three sintering conditions; three sintering temperatures (1100,

1200 & 1300 °C) and three sintering times (1 hr, 2 hr & 3 hr). The X-

ray diffraction analysis and Scanning Electron Microscopy were used

for phase identification of Manganese Zinc Ferrites. The physical

properties, density and shrinkage of the sample pellets have been

studied by dimensional method and porosity by boiling water

method.

Keywords—Powder Metallurgy, Manganese Zinc ferrite, (Mn(1-

x)Znx)Fe2O4.

I. INTRODUCTION

ODAY, magnetic materials are found in numerous

products around us- home appliances, electronic products,

automobiles, communication equipments and data processing

devices and equipments. These materials have now become a

vital part of everyday life in modern industries. The magnetic

materials used in early applications were metallic magnetic

materials. But for frequencies exceeding MHz, metals and

alloys are generally not suitable as soft magnets, as the eddy

current losses are very high. The development of ferrites since

1946 reported that electrical resistivities of ferrites over a

million times those of metals has an enormous impact in the

application of magnetic materials particularly at high

frequencies. Ferrites are used today in radio and television,

microwave and satellite communication, bubble devices,

audio, video and digital recording and as permanent magnets

[1].

Saw Mya Ni is with Metallurgical Research and Development Center, Nay

Pyi Taw, Myanmar (e-mail: [email protected]).

Kay Thi Lwin, Pro- Rector, is with Technological University (TU)

Thanlyin (e-mail: [email protected]).

II. EXPERIMENTAL PROCEDURE

The experimental procedure of Mn-Zn ferrite is shown with

the schematic flow diagram as follows:

Fig. 1 Flow Diagram of Experimental Procedure

Raw Materials Preparation

Manganese dioxide (MnO2), zinc oxide (ZnO) and ferric

oxide (Fe2O3) were used as raw materials for production of

Mn-Zn ferrite. The starting powers were technical grade of

MnO2, ZnO and Fe2O3 were 93.22%, 84.54%, and 80.33%.

MnO2 is reduced to MnO because manganese oxide (MnO) is

not easily available in local market. MnO2 (-270#) mixed with

high quality coke (-48+ 65#) under reducing atmosphere.

Powder metallurgy method was used for production of Mn-

Zn ferrite. The raw materials (MnO, ZnO, Fe2O3) were dried

and weighed in stiochiometric ratio and then wet mixed in

acetone medium for 1-2 hr to obtain thorough and

homogeneous mixing.

3% PVA solution was added as a binder for improving

compaction to the mixed powder and 5% PEG solution was

added as a lubricant to prevent powders and die friction.

The mixed powder was palletized at 30 MPa pressure by

hydraulic press machine and sintered in a high temperature

Production of Manganese-Zinc Ferrite Cores for

Electronic Applications

Saw Mya Ni, and Kay Thi Lwin

T

World Academy of Science, Engineering and Technology 22 2008

150

10 20 30 40 50 60 70

0

20

40

60

80

100

1200

400

800

1200

16000

400

800

1200

1600

Std(Mn-Zn)Fe2O4

2θ Degree

Fe2O3

Intensity

F - Unreacted Fe2O3

F FFFFFFF

1100 oC, 2hr

10 20 30 40 50 60 70

0

20

40

60

80

100

1200

400

800

1200

16000

400

800

1200

1600

Std(Mn-Zn)Fe2O4

2θ Degree

Fe2O3

Intensity

F

F - Unreacted Fe2O3

FFFFF

FFF

1100 oC, 1hr

10 20 30 40 50 60 70

0

500

1000

1500

2000

2500

30000

500

1000

1500

2000

2500

3000MnO

2θ Degree

MnO2

Intensity

10 20 30 40 50 60 70

0

20

40

60

80

100

120

0

400

800

1200

1600

Std(Mn-Zn)Fe2O4

Intensity

2θ Degree

1100 oC, 3hr

muffle furnace at three different sintering temperature of

1100°C, 1200°C and 1300°C and three sintering time 1hr, 2hr

and 3hr respectively in order to achieve desirable physical

properties and low porosity.

The sintered pellets were characterized by X- ray diffraction

analysis and scanning electron microscopy for phase

identification. The physical properties, the density and

shrinkage were measured by dimensional method. The

porosity was measured by boiling water method.

The electrical and magnetic properties; resistivity, relative

permeability, magnetization, coercive force, remanence,

magnetic flux density, magnetic field intensity and B-H

characteristics were also measured.

III. RESULTS AND DISCUSSION

X-ray diffraction analysis was used for characterization of

phases. MnO phase was confirmed by X- ray diffraction

analysis as shown in Fig. 2.

Fig. 2 XRD Pattern of MnO Compared with that of MnO2 Powder

Pattern

Fig. 3 XRD Pattern of Mn-Zn Ferrite Sintered at 1100oC for 1hr

Compared with that of Standard JCPDF Data and Starting Powder

Pattern

The following graphs are the XRD patterns of manganese

zinc ferrite at different sintering times and temperatures. Fig. 3

shows X- ray diffraction analysis of Mn-Zn ferrite sintered at

1100°C for 1hr. Unreacted Fe2O3 phases were observed at that

sintering condition showing this sintering temperature and time

is not sufficient.

Fig. 4 XRD Pattern of Mn-Zn Ferrite Sintered at 1100o C for 2hr

Compared with that of Standard JCPDF data and Starting Powder

Pattern

Fig. 4 shows X- ray diffraction analysis of Mn-Zn ferrite

sintered at 1100°C for 2hr. At this sintering temperature and

time, unreacted Fe2O3 phases were also observed. This shows

that the sintering 1100ºC and sintering time 2hrs was also not

sufficient.

Fig. 5 XRD Pattern of Manganese Zinc Ferrite Sintered at

1100o C for 3hr Compared with that of Standard JCPDF data

Fig. 5 shows X-ray diffraction analysis of Mn-Zn ferrite

sintered at 1100°C for 3hr. At this sintering temperature and

sintering time, all the starting powders were completely

reacted and spinel phases formation was confirmed.


151

10 20 30 40 50 60 70

0204060801001200

400800120016002000

0

400800

12001600

20000

400800120016002000

Std(Mn-Zn)Fe2O

4

2θ Degree

1200 oC, 1hr

1200 oC, 2hr

Intensity

1200 oC, 3hr

Fig. 6 XRD Pattern of Mn-Zn Ferrite Sintered at 1200oC for 1hr,

2hr & 3hr Compared with that of Standard JCPDF Data

Fig. 7 XRD Pattern of Mn-Zn Ferrite Sintered at 1300o C for 1hr,

2hr & 3hr Compared with that of Standard JCPDF Data

Fig. 6 shows XRD pattern of manganese zinc ferrite sintered

at constant temperature1200°C by varying the sintering time

for 1hr, 2hr and 3hr. At this temperature, spinel phases were

confirmed for all the sintering time.

Fig. 7 shows XRD pattern of Mn-Zn ferrite sintered at

constant temperature, 1300°C by varying sintering time for

1hr, 2hr and 3hr. The optimum sintering condition for Mn-Zn

ferrite was observed at 1300°C for 3hr from the nature of the

peak of X- Ray pattern.

Fig. 8 Composite XRD Pattern of Mn-Zn Ferrite Sintered at

Optimum Sintering Condition of 1300ºC for 3 hr

Fig. 8 shows the composite XRD pattern of (Mn(1-

x)Zn(x))Fe2O4 for x = 0.5 composition at optimum sintering

condition of 1300ºC and sintering time 3hr. The ferrite pattern

of Mn-Zn ferrite indicates the consistency with that of pure

end member Mn ferrite and Zn ferrite spinels.

Physical Properties

The results of the measurement of physical properties of

Mn-Zn ferrite are presented in Figs. 9 to 12.

The graphs shown in Figure indicate the increasing of the

density and shrinkage of the sintered pellets with increasing of

the sintering conditions; times and temperatures.

But the porosity decreases as the sintering condition

increases as shown in Fig. 12. All these graphs confirm that the

physical properties increase with increasing of the sintering

time and temperature.

The maximum sintering temperature of 1300°C and 3hr

sintering time gives the 94% of theoretical density for (Mn(1-

x)Zn(x))Fe2O4, x = 0.5.

10 20 30 40 50 60 70

0204060801001200

400

800

1200

1600

20000

400

800

1200

1600

20000

400

800

1200

1600

2000

Std(Mn-Zn)Fe204

2θθθθ Degree

1300 oC, 1hr

1300 oC, 2hr

Intensity

1300 oC, 3hr

10 20 30 40 50 60 70

0

750

1500

2250

3000

0

750

1500

2250

3000

0

750

1500

2250

3000

0

750

1500

2250

3000

0

750

1500

2250

3000

Degree (2θ)

X=0

X=0.25

X=0.5

Intensity

X=0.75

(Mn(1-x)

Zn(x))Fe

2O

4

X=1


152

Fig. 9 Variation of Density with Different Sintering Condition for

Mn-Zn Ferrite

Fig. 10 Variation of Shrinkage in Diameter of Sintered Pellet at

Different Sintering Condition

Fig. 11 Variation of Shrinkage in Thickness of Sintered Pellets at

Different Sintering Condition

Fig. 12 Variation of Porosity with Different Condition for Mn-Zn

Ferrite

Spinel Phase Identification by Scanning Electron

Microscopy

The scanning electron micrographs of manganese zinc

ferrite were given in following figures.

1100 1150 1200 1250 13003.7

3.8

3.9

4.0

4.1

4.2

4.3

4.4

4.5

4.6

4.7

4.8

4.9

5.0

Theorectical density - 5.009 g/cm3

Density, g/cm

3

3hr

2hr

1hr

Sintering Temperature, oC

1hr

2hr

3hr

1100 1150 1200 1250 1300

1.4

1.5

1.6

1.7

1.8

1.9

2.0

2.1

ds - Diameter of sintered pellet

dg - Diameter of green pellet

Shrinkage in D

iameter, m

m, (d

g-d

s)

3hr

2hr

1hr

Sintering Temperature,oC

1hr

2hr

3hr

1100 1150 1200 1250 1300

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

3hr

2hr

1hr

% Porosity

Sintering Temperature, oC

1hr

2hr

3hr

1100 1150 1200 1250 1300

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Sintering Temperature,oC

3hr

2hr

1hrtg - Thickness of green pellet

ts - Thickness of sintered pellet

Shrinkage in Thickness, mm, t g- t s

1hr

2hr

3hr


153

Fig. 13 SEM Micrograph of Mn-Zn Ferrite Sintered at 1200oC & 3hr

with 10µ Scale

Fig. 13 shows scanning electron micrograph of manganese

zinc ferrite sintered at 1200°C & 3hr with 10µ scale. Some

pores can be seen this condition. The average grain size is

3.2µm.

Fig. 14 SEM Micrograph of Mn-Zn Ferrite Sintered at 1250oC &

2hr with 10µ Scale


zinc ferrite sintered at 1250°C and 2hrs with 10µ scale. The

average grain size is 4µm. Porosity decreases with increasing

sintering time and temperature. The average grain size is 4µm.

Fig. 15 SEM Micrograph of Mn-Zn Ferrite Sintered at 1250oC & 2hr

with 5µ Scale


zinc ferrite sintered at 1250°C and 2hrs with 5µ scale just to

enlarge the surface morphology.

Fig. 16 SEM Micrograph of Mn-Zn Ferrite Sintered at 1300oC &

3hr with 10µ Scale


zinc ferrite sintered at 1300°C and 3hrs with 10µ scale.

Average grain size is 6.9µm. By increasing sintering time and

temperature, grain growth increases and the average grain size

increases from 3.2µm in Fig. 13 to 6.9µm in Fig. 16.


154

Magnetic Properties

Fig. 17 The Variation of Electrical Resistivities of Mn-Zn Ferrite

Depending on the Zn Addition

The variation of the electrical resistivity (ρ) with increasing

the composition of zinc ferrite, at room temperature, is

represented in Fig. 17. It is obvious that the electrical

resistivity is decreased rapidly by adding zinc ferrite.

Fig. 18 Variation in Relative Permeability with Different

Compositionfor Mn-Zn Ferrite Spinel

The composition dependence of the relative permeability at

room temperature is represented in Fig. 18. Maximum relative

permeability of (Mn(1-Zn(x))Fe2O4 was observed at ZnFe2O4

composition 0.25.

The typical hysteresis loop of Mn-Zn ferrite using the

measured data with oscilloscope is presented in Fig. 19. The

magnetic properties of manganese zinc ferrite was observed

high permeability, small coercive field, small remanence, small

hysteresis loop, rapid response to high-frequency magnetic

fields and low electrical resistivity.

Fig. 19 Typical Hysteresis Loop of Mn-Zn Ferrite

IV. CONCLUSION

The sintering characteristics, physical properties, X-ray

diffraction analysis and scanning electron microscopy as phase

characterization techniques were studied. The fabrication of

Mn-Zn ferrites (Mn(1-x)Zn(x))Fe2O4 have been studied at

different sintering conditions. The optimum sintering condition

was obtained at 1300ºC and 3h. The density and shrinkage of

the sintered pellets are increased with the increasing of

sintering time and temperature. Maximum relative

permeability of (Mn(1-x)Zn(x))Fe2O4 was observed at ZnFe2O4

composition 0.25. The porosity was decreased with increasing

of sintering time and temperature. The electrical resistivity of

MnFe2O4 is decreased rapidly by adding zinc ferrite. The

magnetic properties of (Mn-Zn) Fe2O4 are more or less in the

range of standard value. The nature of the B-H curve also

agrees with the nature of the standard B-H characteristic of

(Mn-Zn)Fe2O4.

REFERENCES

[1] Heck, C. 1974. Magnetic Materials and their Applications. London:

Butterworths

[2] Donald R. Askeland. 1994. The Science and Engineering of

Materials. 3rd ed.Bostom: PWS Publishing Company.

[3] William .D.Callister, Jr. 1994. Materials Science and Engineering.

[4] Carl A.Keyser. 1986. Materials Science in Engineering

[5] Roberts. J. 1960. High Frequency Application of Ferrites

[6] David Jiles, 1998. Introduction to Magnetism and Magnetic Materials.

2nd ed.U.S.A.: A CRC Press Company.

[7] By Thomas G. Reynolds. No Date. Ferrites.

[8] Kingery. W. D., Bowen. H.K, Uhlmann D.R. 1976. Introduction to

Ceramics.

0.0 0.2 0.4 0.6 0.8 1.0

0

2

4

6

8

10 Sintering temperature at 1300C for 3hr

(Mn(1-x)

Zn(x))Fe

2O

ZnFe2O

4MnFe

2O

4

Electrical Resistivity x 102 (

Ω m

)

XZnFe

2O

4

0.0 0.2 0.4 0.6 0.8 1.0

0.0

0.5

1.0

1.5

2.0

2.5

sintering temperature at 1300oC for 3hr

(Mn(1-x)

Zn(x))Fe

2O

ZnFe2O

4MnFe

2O

4

Relative Perm

eability (

µr)

XZnFe

2O

4


155

Mangan - Zinc Ferrite

Documents

Transcript of Mangan - Zinc Ferrite