Synthesis And Characterization Of Strontium Ferrite Environmental Sciences Essay

Strontium ferrite is a ferromagnetic stuff and reported as holding hexangular magnetoplumbite type ( M-type ) construction. It is the most widely used lasting magnets throughout the universe, which account for approximately 90wt % of the one-year production of lasting magnets. In this survey, the Sr ferrite is synthesized utilizing sol-gel methods and the magnetic belongingss were analyzed.

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Chapter 1 gave debut about the construction of M-type hexangular Sr ferrite. Besides, some general magnetic belongingss will be discussed. Commercial applications of Sr ferrite would be discussed every bit good.

Chapter 2 is all about the experimental inside informations, including the man-made techniques used for Sr ferrite, description of instrument used and processs carried out.

Chapter 3 concentrated on the consequences on magnetic susceptibleness of hexangular Sr ferrite. Comparison between Sr ferrite and cation-substituted Sr ferrite was made.

Chapter 4 concluded the whole probe of this survey. Suggestions for future surveies were besides discussed. Better apprehension of the belongingss and practical applications of Sr ferrite can be achieved through this survey.

Abstraction

The belongingss of magnetoplumbite type ( M-type ) hexangular Sr ferrite has been investigated. The effort of permutation of Co ( II ) oxide and Ti ( IV ) oxide in order to bring forth a quaternate system of the type SrO-Fe2O3-XO where Ten represents the dopant cation was made. The synthesis is based on sol-gel method where ethene ethanediol is the gel precursor. This technique was employed because it was found to be able to bring forth nanoparticles of cation substituted Sr ferrite. Furthermore, sol-gel method can bring forth high outputs of Sr ferrite atoms.

Overall, the magnetic belongingss were observed to be alteration after the cation permutation. Co ( II ) -Ti ( IV ) permutation in SrFe12O19 with different ratios were made in this survey to look into the consequence of cation permutation in magnetic belongingss of Sr ferrite. Co ( II ) -Ti ( IV ) permutation in Sr ferrite with mole ratio of 0.4 showed the best magnetic belongingss that we desired for. The mass susceptibleness where X = 0.4 was found to be increase aggressively compared to the unsubstituted 1. Except the Co Ti permutation with mole ratio of 0.4, other cation permutation ratios showed lessening in mass susceptibleness which is non desirable. Therefore the cobalt-titanium permutation for SrCoxTixFe12-2xO19 with X = 0.4 is the best to better magnetic belongingss of Sr ferrite for assorted commercial applications.

Reappraisal

Strontium ferrite has been a topic of uninterrupted involvement and intensive survey for several decennaries due to the fact that this compound has been the the most widely used lasting magnets, which account for approximately 90wt % of the one-year production of lasting magnets since shortly after its find in the fiftiess. Strontium hexaferrite, SrFe12O19, is a ferrimagnet and is besides known as ceramic lasting magnet. When compared with alnico-magnets, Sr ferrite has high coercivity, moderate remenance, corrosion opposition and first-class chemical stableness [ 5 ] . Iron ( III ) oxide ( Fe2O3 ) is the chief constituents in SrFe12O19 which gives rise to its magnetic belongingss. Within the five different crystallographic sites of Sr ferrite, the Fe ions are coupled antiferromagnetically. Due to its high magnetocrystalline anisotropy field in its construction, SrFe12O19 exhibits high impregnation magnetisation and high coercivity [ 1 ] . The high magnetic permeableness in Sr ferrite enables it to hive away strong magnetic Fieldss, which is stronger than Fe. Strontium ferrite is frequently produced as nanoscale size pulverization, which can be sintered into solid nucleuss.

Strontium ferrite has been used for several of import industrial applications, such as lasting magnets, microwave devices and high denseness perpendicular entering media, with proper doping in order to better belongingss of Sr ferrite [ 1 ] . SrFe12O19 has besides been investigated as a medium for magnetic recording and magneto-optical recording and for long ( millimeter ) -wave devices [ 2 ] . Attempts have made to the development of fresh man-made methods which facilitate the production of all right hexangular ferrite atoms and to possible ways of cut downing their high intrinsic magnetocrystalline anisotropy.

The aim in this survey was to try the synthesis of cation substituted M-type hexangular ferrite SrCoxTixFe12-2xO19 utilizing the sol-gel method. The sol-gel method has been used widely to bring forth all right atoms of a assortment of oxides. The consequence of doping Sr ferrite with Co ( II ) and Ti ( IV ) oxides to bring forth quaternate systems of SrO-Fe2O3-XO, where Ten represents the dopant cation would be tested. The all right atoms of cation substituted ferrite produced by utilizing sol-gel technique is desirable because the grain size of the stuffs used in magnetic recording is the chief factor finding the degree of background noise at low denseness.

Magnetic belongingss of Sr ferrite would be focus in this survey. Magnetic susceptibleness balance would be used to find the mass susceptibleness for both strontium ferrite and cation-substituted Sr ferrite produced utilizing the sol-gel method. The mass susceptiblenesss of the samples were compared to find the optimal sum of cation needed to dope to ferrite to give the best magnetic behavior.

CRYSTAL STRUCTURE OF M-TYPE HEXAGONAL SrFe12O19

Harmonizing to crystalline construction, hexaferrite can be classified into four types, these include M, W, Y and Z types hexaferrites which correspond to ( SrO + MeO ) : Fe2O3 ratios of 1:6, 3:8, 4:6 and 5:12 severally. SrFe12O19 is classified as M-type hexaferrite.

The hexangular SrFe12O19 was foremost prepared by AdelskA?old in 1938 [ 2 ] . He besides confirmed that the crystal construction of this compound to be iso-structural with the of course happening ferrite mineral magnetoplumbite, and hence it has the M-type construction. Subsequently structural polishs for Sr hexaferrite have confirmed his finding [ 2 ] . Strontium ferrite is classified as hexangular ferrite. It is denoted as holding the infinite group P63/mmc. Harmonizing to the research made by Kimura et Al, the lattice parametric quantities measured are found to be: a = 0.588 36nm and c = 2.303 76nm at room temperature [ 2 ] .

As shown for M-type hexaferrite BaFe12O19 in Fig. 1.1, the crystalline constructions of different types of hexaferrites are unusually complex. The unit cell contains 10 O beds. A unit cell is consecutive constructed for four blocks, they are S ( spinel ) , R ( hexangular ) , S* and R* . The S and R blocks have tantamount atomic agreements and are rotated around the c-axis at 180A° with regard to S* and R* blocks. Roentgen or R* block consists of three O2a?’A beds while S or S* block contains two O2a?’A beds ; with one O site in the in-between bed substituted by a Ba2+A ion [ 16 ] . The construction of Sr ferrite is similar to that of Ba ferrite, by merely replacing the Ba ion with strontium ion.

Fig.A 1.1: A Structure of Ba hexaferrite

Occasionally, a unit cell is comprises of two formula units. The unit cell consists of 64 ions per hexangular unit cell, which are 2 strontium ions, 38 O ions and 24 ferrous ions. The construction of magnetoplumbite are made of a bed of hexangular close jammed agreement of O and Sr ions, which is sandwiched between two spinal blocks incorporating a three-dimensional close-packed agreement of O atoms with Fe atoms.

The Fe atoms are positioned at five interstitial crystallographically different cation sites of the close-packed beds, viz. 4f1 ( tetrahedral site, A sites ) , 12k, 4f2, 2a ( octahedral sites, B sites ) and 2b ( rhombohedral bipyramidal site ) [ 15 ] . The tetrahedral Fe oxide is FeO4, octahedral Fe oxide consists of six O ions, which is FeO6, and the expression for rhombohedral bipyramidal Fe oxide is FeO5. A conventional M-type structural representation and the five Fe3+ sites are shown in Fig. 1.2 by Collomb et Al. [ 15 ] .

Figure 1.2: The crystal construction study map of the hexangular M-type stage and the five Fe sites with their milieus are displayed.

The 2b sites merely occur in the same bed with strontium ion. 12k site is the octahedral site of S and R blocks. There are two tetrahedral ( 4f1 ) sites and one octahedral ( 2a ) site in Centre of S block. The two octahedral ( 4f2 ) sites are found in the R block, adjacent to the strontium-containing bed.

The M-type construction of strontium ferrite gives rise to its magnetic belongingss. Cation permutation to strontium ferrite may give opportunities whereby changing the construction and therefore act upon the magnetic belongingss.

MAGNETIC PROPERTIES OF M-TYPE HEXAGONAL SrFe12O19

Strontium hexaferrite is a ferrimagnetic stuff. Since the free negatrons in SrFe12O19 are in close propinquity and remain aligned even the external magnetic field have been removed, it is able to retain a lasting magnetic field and is recognized as ferrimagnetic stuff.

In 1950s Gorter predicted that the Fe ions at the rhombohedral bipyramidal ( 2b ) and octahedral ( 2a, 12k ) sites have their spin orientation antiparallel to that of the Fe ions at the 4f sites [ 2 ] . The antiparallel 4f1 and 4f2 and parallel 2a, 12k and 2b sublattices form the ferrimagnetic construction. The magnetic ordination corresponding to the magnetoplumbite construction of hexangular Sr ferrite is good illustrated in Fig. 1.3.

In S block, the bulk I±-sublattice consists of four octahedral ions and the minority I?-sublattice contains two tetrahedral ions whereas R block contributes three octahedral ions and one rhombohedral ion to the bulk sublattice and two octahedral ions to the minority sublattice.

Figure 1.3: The conventional construction ( left ) of the SrFe12O19 with Gorter ‘s magnetic ordination ( in-between ) along the c-axis. The big unfastened circles are oxygen ions, the big broken circles are Sr ions ; little circles with a cross inside represent Fe ions at 12k, little circles incorporating a filled circle inside represent Fe ions at 4f2, little unfilled circles represent Fe ions at 4f1, filled little circles represent Fe ions at 2a and little circles with a unfilled circle inside represent Fe ions at 2b. The magnetic construction suggested by Gorter is shown on the right, where the pointers represent the way of spin polarisation.

From Fig. 1.3, we can sum up the sites of Fe ( III ) ions matching to the spin way, as in Table 1.1.

Site

Coordination

Occupancy

Direction of spin polarisation

12k

Octahedral

12

Up

2a

Octahedral

2

Up

2b

Trigonal Bypiramidal

2

Up

4f1

Tetrahedral

4

Down

4f2

Octahedral

4

Down

Table 1.1: Fe ( III ) ion sites in M-type hexangular ferrite

Hysteresis Loop

The magnetic belongingss of Sr ferrite can be examined through hysteresis cringles. Hysteresis cringle can be measured utilizing instruments such as Vibrating Sample Magnetometer ( VSM ) and SQUID Magnetometry Measurements.

When a magnetic stuff is placed in a magnetic field, the flux denseness ( B ) would dawdle behind the magnetising force ( H ) that causes it, and this signifier hysteresis cringle.

From a hysteresis cringle, we can place the magnetic belongingss of the stuff, they are saturation magnetisation, remanence or besides known as remnant magnetisation, and coercivity. A typical hysteresis cringle is good illustrated in Fig. 1.4.

Figure 1.4: Typical hysteresis cringle ( B-H curve )

Initially, there is no applied magnetic field and it is known as unmagnetized province. After magnetic field is applied, it causes alignment. Until maximal magnetising force applied, maximal flux denseness achieved at the same clip and this phenomenon is known as impregnation magnetisation. At this point, the maximal figure of spin has mobilized. Saturation magnetisation is defined as the maximal possible magnetization of a stuff. It is besides a step of strongest magnetic field a magnet can bring forth. The unit of impregnation magnetisation is in amperes per metre. Strontium ferrite is holding high impregnation magnetisation at which it can hive away high sum of magnetising force. As the magnetizing force being easy removed, the alliance stays at the point where H = 0, this is known as remnant magnetisation. Remnant magnetisation is the magnetisation left in a lasting magnet after an external magnetic field is removed. When a magnet is “ magnetic ” , it has remanence. It is normally measured in unit Tesla. Strong lasting magnet such as Sr ferrite has high leftover magnetisation which means the high sum of magnetic force remains in it even after the magnetizing force is removed. As signifier Fig. 1.4, negative magnetic field is applied to demagnetise the lasting magnet. When the flux denseness ( B ) = 0, there is no magnetising force remain in the magnet and the negative H needed to demagnetise the magnet is known as coercivity. Negative H is the magnetic field applied in opposite way. Coercivity is measured in unit amperes per metre. Due to its high uniaxial magnetocrystalline anisotropy with an easy axis of magnetisation along the hexangular c-axis in the construction, SrFe12O19 has high coercivity.

Anisotropy is directional or orientational effects in crystal construction of stuffs which can supply better magnetic public presentation along certain preferable axis. Therefore, we need to use high negative magnetising force to demagnetise Sr ferrite. Attempts have to be made to take down down the coercivity of Sr ferrite for use.

Unit of measurements in Magnetism

The units used in magnetic attraction can be divided chiefly into two classs, SI system and c.g.s system. The transition table shown in Table 1.2 is to clear up the magnetic attraction expression in both SI and c.g.s systems and the transition factors between them.

Measure

Symbol

SI Unit

SI Equation

c.g.s Unit

c.g.s Equation

Conversion Factor

Magnetic Initiation

Bacillus

tesla ( T )

B=Aµo ( H+M )

gauss ( G )

B = H+4IˆM

1 T = 104A G

Magnetic Field Strength

Hydrogen

ampere/meterA

( A/m )

H = NA-I/lcA

( lc – magneticA

way, m )

oersted ( Oe )

H = 0.4IˆNA-I/lc

( lc – magneticA

way, centimeter )

1 A/m =A

4 IˆA-10-3A Oe

Magnetic Flux

Wb ( Wb )

I¦ = BA-Ac

( Ac – country, m2A )

Mx ( M )

I¦ = BA-Ac

( Ac – country, cm2A )

1 Wb = 108A M

Magnetization

Meter

ampere/meter ( A/m )

M=m/V

( m- sum magnetic minute, A

V- volume, m3A )

emu/cm3

M=m/V

( m- sum magnetic minute, A

V- volume, cm3A )

1 A/m = 10-3A

electromagnetic unit / cm3

Magnetic Permeability of Vaccum

Aµo

newton/ampere2

Aµo= 4IˆA-10-7

1

4IˆA-10-7

Induction

Liter

H

L=I?oI?N2Ac/lc

( Ac- country, M2, A

lc – magnetic way, m )

H

L=0.4IˆI?N2Ac/lcA-10-8

( Ac-area, cm2, A

lc – magnetic way, centimeter )

1

Emf ( electromotive force )

Volt

V

V=-NA-dI¦/dt

V

V=-10-8NA-dI¦/dt

1

Note: In the above equations, I = current ( in As ) , N = bends

Table 1.2: Magnetism expressions in SI and c.g.s systems and their transition factors for the magnetic units.

1.4 PHOTOLUMINESCENCE PROPERTIES OF SrFe12O19

Harmonizing to the survey of G. B. Teh et.al [ 3 ] on Sr ferrite, Sr ferrite was found to exhibit photoluminescence behaviour. When a sample of Sr ferrite is excited at a certain wavelength, highest strength of photoluminescence emanation extremums was obtained. The ability of Sr ferrite to photoluminesce could be due to the O vacancies in their lattice construction. The O vacancies are assumed to do the atoms to exhibit photoluminescence behaviour by moving as traps for nomadic excitement. The O vacancies have effectual +2 charges, doing them powerful electron gaining control centres. Valence negatron would derive sufficient energy to leap from the valency set to the conductivity set and go forthing a spread known as hole during excitement. F-centers, which is the part where contain high sum of negatrons would organize when the aroused negatrons being trapped in O vacancies. These rich negatron centres would take to emanation of luminescence when the holes and negatrons recombine.

1.5 SYNTHESIS ROUTE OF SrFe12O19

The processing paths used for synthesis of Sr ferrite affect its belongingss much. Traditionally, this ferrite pulverization is synthesized by a assorted oxide ceramic method, which involves the solid-state reaction between SrCO3 and Fe2O3 at a high calcination temperature ( about 1300A°C ) . However, uncontrolled atom morphology, larger atom size and agglomerates would be the biggest disadvantages of this technique. Besides, taint would be introduced to the sample while subsequent milling of the calcined ferrite pulverization and this would impact the magnetic belongingss become less desirable. Therefore, the narrowed atom size distribution, refined atom size and minimum atom agglomeration has been the chief concern during the synthesis of Sr ferrite.

In order to better the magnetic belongingss, legion nonconventional soft man-made paths have been carried out, including sol-gel synthesis [ 3 ] , hydrothermal reaction [ 6 ] , co-precipitation [ 7 ] , citric acid method [ 8 ] and microemulsion processing [ 10 ] .

In this survey, the synthesis of Sr ferrite employed the sol-gel technique. It is a wet chemical path using ethylene ethanediol as gel precursor. Sol-gel technique is the technique of utilizing chemical substances which have high solubility in organic dissolvers to synthesise precursor compounds. The compounds are easy transformed into hydrated oxides on hydrolysis. The metal alkoxides formed can be removed easy utilizing hydrolysis and thermic intervention and therefore consequences in hydrous oxides which are extremely purify.

Sol-gel method is used in this survey because of its many advantages. Sol-gel technique is able to bring forth homogenous nanosized crystallites. This method is tend to give molded stuffs straight from a solution without go throughing through the pulverization processing and the fact that the annealing temperature is really low compared with other conventional engineering. The crystalline size and belongingss of the ferrite produced are mostly affected by calcinations temperature [ 3 ] . Sol gel method has the advantage that the crystal growing of atoms is easier to command by changing the heat intervention [ 11 ] . It was reported that at 500EsC it produced merely maghemite, I?-Fe2O3. A assorted merchandise of magnetic I±-Fe2O3 and M-type SrFe12O19 were obtained at 600EsC. As the calcination temperature addition to 800EsC and supra, there are merely M-type SrFe12O19 stage was observed. Sol-gel synthesis is able to bring forth high outputs of SrFe12O19 nanoparticles. It is besides able to bring forth nanocrystallite of cation substituted SrFe12O19. Nanoparticle size of Sr ferrite is desirable and aimed to synthesise because nanoparticles tend to give better magnetic belongingss. Nanoparticles give few magnetic spheres, likely individual sphere. Single sphere tends to give higher magnetic initiation because there are no oppose magnetic sphere. Single sphere aligns in one way merely. These belongingss are ideal for the devising of lasting magnet.

1.6 CATION SUBSTITUTION IN SrFe12O19

In order to better the magnetic belongingss of Sr ferrite, many surveies have been carried out. One of them is cation permutation in Sr ferrite. Rare Earth and other metal cations are used for permutation for Sr and Fe severally [ 5 ] . The brace doping of SrFe12O19 such as a La-Co brace to replace a Sr-Fe brace has been tested [ 14 ] . The doping, or known as cation permutation, is aim to better the magnetic belongingss of Sr ferrite. Cation permutation consequences in structural alterations in Sr ferrite. As the physical belongingss of ferrite alteration, the magnetic belongingss would be affected due to the fact that magnetic belongingss are determined by the agreement of Fe ions in crystal construction. In this survey, Co-Ti brace will be doped to the Sr ferrite. Cobalt Ti permutation will bring forth a quaternate system of the type SrO-Fe2O3-AO where A represents the dopant cation.The Co Ti permutation gives rise to the new expression, SrCoxTixFe12-2xO19 where Ten is the figure of mole of cation substituted in.

1.7 Commercial Applications

Strontium ferrite is widely used as lasting magnet because it has way of easy magnetisation and the hexangular c-axis which are perpendicular to the plane of the home base. The belongingss that are desirable in utilizing as lasting magnet include high impregnation magnetisation, high leftover magnetisation, high coercivity, high Curie temperature and high magnetocrystalline anisotropy.

Besides, SrFe12O19 is besides normally used in high-density informations storage magnetic entering media. Nanoparticles of SrFe12O19 with individual sphere and low coercivity are important in used for magnetic recording media. M-type Sr ferrite nanoparticles have attracted much attending due to their good frequence characteristic, low noise, high end product, in peculiar, first-class high frequence characteristic and broad dynamic frequence scope [ 4 ] . There are two types of entering medium, viz. particulates and thin movies. Tape and floppy is categorized in particulate and difficult thrust is belongs to thin movie. Information is stored by magnetising stuff. The entering caput can use magnetic field ( H ) and align spheres to magnetise the medium. It can besides observe a alteration in the magnetisation of the medium. Magnetic entering media prefers high impregnation magnetisation ; do it to hive away as much information. High value of remnant magnetisation is required in entering media to do certain that all stuffs stored in the difficult disc still remained even the power supply ( applied magnetic field ) is switched away. Low coercivity is of import in magnetic recording media. When the positive magnetic field is applied, this charging manages the medium to hive away informations. On the other manus, negative magnetic field applied to recover back the information, this is called discharges. Therefore, less current is needed to recover the information in the low coercivity medium. As a consequence, less heat generated and this saves the electricity.

In general, Sr ferrite has high value of uniaxial anisotropy field, high coercive force and high impregnation magnetisation. The high coercivity of Sr ferrite has to be lowered down and impregnation magnetisation has to be at the same time increased if it is to be utile for magnetic recording intents. It has been reported that the permutation of cations such as Co ( II ) for the ion Fe ( III ) in Sr ferrite has lowered the coercive force. Therefore, many surveies were carried out to accomplish better magnetic belongingss of Sr ferrite for commercial applications.

Chapter 2: EXPERIMENTAL

Sample Preparation

Synthesis of M-type SrFe12O19

Synthesis of Cation Substituted SrFe12O19

Sample Characterization

Magnetic Susceptibility Balance MK1

2.1 Sample Preparation

2.1.1 Synthesis of M-type SrFe12O19

The sol-gel technique was used to synthesise M-type SrFe12O19 whereby the ethene ethanediol acts as gel precursor. The starting stuffs, Sr nitrate, Sr ( NO3 ) 2 and Fe ( III ) nitrate-9-hydrates, Fe ( NO3 ) 3A·9H2O were used due to their high solubility in ethylene ethanediol. Calculation below was made to find the weight of stuffs needed to be used.

Relative Molecular Mass of stuffs:

Strontium nitrate, Sr ( NO3 ) 2 = 211.63 g/mol

Iron ( III ) nitrate-9-hydrates, Fe ( NO3 ) 3A·9H2O = 404 g/mol

( Note: All replies have to be converted into 3 important figures. )

No. of mol of 1 g Sr ( NO3 ) 2 = Mass of Sr ( NO3 ) 2

RMM of Sr ( NO3 ) 2

= 1g

211.63g/mol

= 4.7252×10-3 mol

Strontium: Fe = 1: 12

No. of mol of Fe ( NO3 ) 3A·9H2O needed = 4.7252×10-3 mol x 12

= 5.6702×10-2 mol

Mass of Fe ( NO3 ) 3A·9H2O needed = No. of mol of Fe ( NO3 ) 3A·9H2O needed ten RMM of

Fe ( NO3 ) 3A·9H2O

= 5.6702×10-2 mol x 404g/mol

= 22.9 g

From the computation, 1g of Sr nitrate and 22.9g of Fe ( III ) nitrate-9-hydrates were needed in the synthesis and were weighted. Strontium nitrate would supply 1 mol of Sr ions and Fe ( III ) nitrate-9-hydrates would supply 12 mol of Fe ions in the synthesis of Sr ferrite, which matched the molecular expression of SrFe12O19. The Sr nitrate and Fe ( III ) nitrate-9-hydrates were readily dissolved in ethene ethanediol with little heat applied due to their high solubility in it. The mixture was heated somewhat and stirred with a magnetic saloon until the mixture was to the full dissolved. The attendant solution is in crystalline ruddy colour. The magnetic stirring saloon was removed.

The mixture was heated to 100A°C and it would easy transform into a gel signifier. The gel was dried with uninterrupted heating at 100A°C for 3 hours. The dried gel was so transferred to a crucible to take hints of organic precursor. A mixture of metal oxides in spread nanoclusters signifier was obtained. The dried gel was so annealed in a furnace at 800A°C for 3 yearss with extended land with a stamp in a howitzer after annealed at interval of each twenty-four hours.

2.1.2 Synthesis of Cation Substituted SrFe12O19

Cation substituted strontium ferrite was synthesized by utilizing Co ( II ) ions and Ti ( IV ) ions to replace the Fe ions in M-type hexangular Sr ferrite. The permutation of Co ( II ) and Ti ( IV ) gives the compound a new molecular expression, which is SrCoxTixFe12-2xO19 where the x denoted different ratios. In the synthesis of cation substituted SrFe12O19, the ratios of cations used, x, is in between 0.2 to 6.0 ( 0.2 a‰¤ x a‰¤ 6.0 ) , where ten = 0.2, 0.4, 0.6, 0.8, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0. The same method described in subdivision 2.1.1 was used for the synthesis, by merely adding two new get downing stuffs, which are the Co ( II ) nitrate and Ti ( IV ) ethoxide to give the Co2+ and Ti4+ cations.

Calculation as described below was made to cipher the weight of stuffs needed severally.

Relative Molecular Mass of stuffs:

Strontium nitrate, Sr ( NO3 ) 2 = 211.63 g/mol

Iron ( III ) nitrate-9-hydrates, Fe ( NO3 ) 3A·9H2O = 404 g/mol

Cobalt ( II ) nitrate, Co ( NO3 ) 2.6H2O = 291.04 g/mol

Titanium ( IV ) ethoxide, Ti ( CC2H5 ) 4 = 228.11 g/mol

( Note: All replies have to be converted into 3 important figures. )

Examples used for the computation: SrCo0.2Ti0.2Fe11.6O19, x= 0.2

No. of mol of 1 g Ti ( CC2H5 ) 4 = Mass of Ti ( CC2H5 ) 4

RMM of Ti ( CC2H5 ) 4

= 1g

228.11g/mol

= 4.3838×10-3 mol

0.2 mol of Ti needed 1 mol of Sr.

4.3838×10-3 mol of Ti needed ( 4.3838×10-3 mol x 1 ) mol of Sr.

0.2

Therefore, 0.021919 mol of Sr is needed.

Mass of Sr ( NO3 ) 2 needed = 0.021919mol ten 211.63 g/mol

= 4.64 g

0.2 mol of Ti needed 11.6 mol of Fe.

4.3838×10-3 mol of Ti needed ( 4.3838×10-3 mol x 11.6 ) mol of Sr.

0.2

Therefore, 0.25426 mol of Fe is needed.

Mass of Fe ( NO3 ) 3A·9H2O needed = 0.25426mol ten 404g/mol

= 103 g

Mass of Co ( NO3 ) 2.6H2O needed = 4.3838×10-3 mol x 291.04g/mol

= 1.28 g

The computation above were used to cipher the weight of get downing stuffs needed for other cation ratios, ten for 0.4, 0.6, 0.8, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 severally every bit good. The weight needed for each stuff was tabulated in Table 2.1.

ten

Weight of stuffs needed ( g )

Sr ( NO3 ) 2

Fe ( NO3 ) 3A·9H2O

Co ( NO3 ) 2.6H2O

0.2

4.64

103

1.28

0.4

2.32

51.4

1.28

0.6

1.55

31.9

1.28

0.8

1.11

23.0

1.28

1.0

0.93

17.7

1.28

2.0

0.46

7.08

1.28

3.0

0.31

3.54

1.28

4.0

0.23

1.77

1.28

5.0

0.19

0.71

1.28

6.0

0.15

0.00

1.28

Table 2.1: Weight of stuffs needed for synthesis of Co ( II ) -Ti ( IV ) substituted Sr ferrite

For the series of different permutation ratios ( ten ) , the corresponding Sr nitrate, Fe ( III ) nitrate-9-hydrates, Co ( II ) nitrate and Ti ( IV ) ethoxide were weighed and dissolved in 100ml ethene ethanediol. The oxides obtained after ignition were so annealed in a furnace at 800A°C for 3 yearss with extended land with a stamp in a howitzer after annealed at interval of each twenty-four hours. The readying for Sr ferrite and cation substituted strontium ferrite is shown in Fig. 2.1 in flow chart array.

Figure 2.1: Conventional diagram of the process for synthesis of Sr ferrite and cobalt-titanium substituted SrFe12O19.

Sample Characterization

Magnetic Susceptibility Balance MK1

The magnetic belongingss of Sr ferrite and cobalt-titanium substituted Sr ferrite produced by the method described above were examined utilizing the Magnetic Susceptibility Balance MARK 1 ( MK1 ) by Sherwood Scientific Ltd, England. The magnetic susceptibleness balance setup was shown in Fig. 2.2.

Figure 2.2: Magnetic Susceptibility Balance MK1 by Sherwood Scientific Ltd, England.

The basic design rule of Magnetic Susceptibility Balance MK1 was shown in Figure 2.3. Magnetic Susceptibility Balance determines the magnetic belongingss by puting two twosome of traveling magnets with the beam in between where the stationary sample is ready to be measured. Basically, the possible warp in the beam and the motion being made of a peculiar sample either solid or liquid could be observed in a balanced system which possesses a magnetic field. Meanwhile, the spiral within the instrument is conducted with current required in order to do compensation of the magnetic force produced by the sample. Either paramagnetic or diamagnetic could be resolved in a asset or minus comparatively on show with the assistance of the way that the beam Swift.

Figure 2.3: Basic design rule of Magnetic Susceptibility Balance MK1 by Sherwood Scientific Ltd, England.

Magnetic susceptibleness is defined as when the magnetising field is applied to the sample, how much is the ratio of the strength of magnetic attraction induced by the sample in response to the magnetising field which it is capable. In this experiment, mass susceptibleness was the chief concern. Mass susceptibleness, xg, is defines by the mathematical expression below:

??‘?g= ??‘?v/d

Where vitamin D = denseness of substance

??‘?v is the volume susceptibleness, calculated by utilizing the expression:

??‘?v = I/H

Where I = strength of magnetic attraction produced in a substance

H = strength of applied magnetic field

Based on the magnetic belongingss of magnetic substances, they can be classified into one of the three groups. Among them, there is paramagnetic stuff which would pull by a strong magnetic field, diamagnetic which repelled by magnetic field and ferromagnetic which is alone to retain their ain magnetic field. After the external magnetic field is removed, ferromagnetic stuffs are still able to retain a lasting magnetic field. This is happened due to their free negatrons are in close propinquity and remain aligned without the magnetic field. Strontium ferrite and cobalt-titanium substituted Sr ferrite were found to be ferromagnetic due to the overshooting value observed on the show when the samples were introduced. To get the better of this job, a non-magnetic stuff Na chloride, was used to ‘dilute ‘ the big magnetic attraction induced by the samples.

Procedure was carried out. First, the scope boss of Magnetic Susceptibility Balance MK1 was turned to the x1 graduated table and was allowed to warm up for 10 proceedingss before usage. The nothing boss is adjusted until the show reads 000. An empty sample tubing of known weight was placed into the tubing usher and the reading, Ro was taken. 0.0005g sample + 0.2820g NaCl ( sample length, fifty =3cm ) was packed into the sample column. The weight of samples and Na chloride were fixed for all measurings made. The jammed sample tubing was placed into tubing usher and the reading, R was taken. The stairss were repeated for all the 11 samples.

The mass susceptibleness, ??‘?g is calculated utilizing the expression:

??‘?g= CBal* cubic decimeter * ( R-Ro )

109 * m

Where: cubic decimeter = length of sample ( centimeter )

m = mass of sample ( gm )

R = balance reading for sample + tubing

Ro = balance reading for empty tubing

CBal = the balance standardization changeless ( =1 )

Chapter 3: Consequence AND DISCUSSION

3.1 Consequences of Mass Susceptibility

3.1.1 Mass susceptibleness of M-type SrFe12O19

3.1.2 Mass susceptibleness of Cation Substituted SrFe12O19

3.1.3 Table of mass susceptibleness of SrFe12O19 and Co ( II ) -Ti ( IV )

substituted SrFe12O19

3.1.4 Graph of mass susceptibleness, ??‘?g ( cgs ) against Co ( II ) -Ti ( IV ) ratio

3.2 Findingss and Discussion

3.1 RESULTS OF MASS SUSCEPTIBILITY

Mass susceptiblenesss of the samples were calculated utilizing the expression:

??‘?g= CBal* cubic decimeter * ( R-Ro )

109 * m

Where: cubic decimeter = sample length ( centimeter )

m = sample mass ( gm )

R = balance reading for sample in tubing

Ro = balance reading for empty tubing

CBal = the balance standardization changeless ( =1 )

* All the replies are adjusted to 4 important figures.

3.1.1 Mass Susceptibility of M-type SrFe12O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ 936- ( -036 ) ]

109 x 0.0005

= 1.944×10-4

3.1.2 Mass Susceptibility of Cation Substituted SrFe12O19

SrCo0.2Ti0.2Fe11.6O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ 798- ( -036 ) ]

109 x 0.0005

= 1.668×10-4

SrCo0.4Ti0.4Fe11.2O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ 671- ( -036 ) ]

109 x 0.0005

= 1.414×10-4

SrCo0.6Ti0.6Fe10.8O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ 654- ( -036 ) ]

109 x 0.0005

= 1.380×10-4

SrCo0.8Ti0.8Fe10.4O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ 542- ( -036 ) ]

109 x 0.0005

= 1.156×10-4

SrCo1.0Ti1.0Fe10O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ 441- ( -036 ) ]

109 x 0.0005

= 0.954×10-4

SrCo2.0Ti2.0Fe8O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ 236- ( -036 ) ]

109 x 0.0005

= 0.544×10-4

SrCo3.0Ti3.0Fe6O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ 162- ( -036 ) ]

109 x 0.0005

= 0.396×10-4

SrCo4.0Ti4.0Fe4O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ 145- ( -036 ) ]

109 x 0.0005

= 0.362×10-4

SrCo5.0Ti5.0Fe2O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ -006- ( -036 ) ]

109 x 0.0005

= 0.060×10-4

SrCo6.0Ti6.0O19

??‘?g = CBal* cubic decimeter * ( R-Ro )

109 * m

= 1 ten 3cm ten [ -066- ( -036 ) ]

109 x 0.0005

= -0.060×10-4

3.1.3 Table of mass susceptibleness of SrFe12O19 and Co ( II ) -Ti ( IV ) substituted SrFe12O19

The mass susceptiblenesss of the samples calculated were summarized in Table 1.

Samples

Sample length, cubic decimeter ( centimeter )

Sample mass, m ( gm )

Empty tubing reading, R0

Reading for tubing + sample, R

Mass susceptibleness, xg

SrFe12O19

0.1

0.0005

-036

936

1.944×10-4

SrCo0.2Ti0.2Fe11.6O19

0.1

0.0005

-036

798

1.668×10-4

SrCo0.4Ti0.4Fe11.2O19

0.1

0.0005

-036

671

1.414×10-4

SrCo0.6Ti0.6Fe10.8O19

0.1

0.0005

-036

654

1.380×10-4

SrCo0.8Ti0.8Fe10.4O19

0.1

0.0005

-036

542

1.156×10-4

SrCo1.0Ti1.0Fe10O19

0.1

0.0005

-036

441

0.954×10-4

SrCo2.0Ti2.0Fe8O19

0.1

0.0005

-036

236

0.544×10-4

SrCo3.0Ti3.0Fe6O19

0.1

0.0005

-036

162

0.396×10-4

SrCo4.0Ti4.0Fe4O19

0.1

0.0005

-036

145

0.362×10-4

SrCo5.0Ti5.0Fe2O19

0.1

0.0005

-036

-006

0.060×10-4

SrCo6.0Ti6.0O19

0.1

0.0005

-036

-066

-0.060×10-4

Table 3.1: Mass susceptibleness, xg of SrFe12O19 and Co ( II ) -Ti ( IV ) substituted SrFe12O19

3.1.4 Graph of mass susceptibleness, ??‘?g ( cgs ) against Co ( II ) -Ti ( IV ) ratio

A graph of mass susceptibleness of SrFe12O19 and Co ( II ) -Ti ( IV ) substituted SrFe12O19 against Co ( II ) -Ti ( IV ) ratio was plotted and shown in Graph 3.1.

Figure 3.1: Graph of mass susceptibleness, ??‘?g ( cgs ) against Co ( II ) -Ti ( IV ) ratio

3.2 FINDINGS AND DISCUSSION

Magnetic susceptibleness is a step of response of negatrons in sample to an applied magnetic field. Electrons produce magnetic minutes at where the negatrons spin circularly around the karyon following right-thumb regulation. The net magmetic minute is the amount of minutes from all negatrons. There are three types of magnetic attraction ; they are ferromagnetic or ferrimagnetic, paramagnetic and diamagnetic. Strontium ferrite is a ferrimagnetic compound due to its high magnetic initiation, B when magnetic field, H is applied. The magnetic minutes of ferrimagnetic Sr ferrite is aligned parallel with applied magnetic field. It is a of course magnet because the magnetic minutes are point at one way even there is no magnetic field is applied. The magnetic minute of M-type hexangular ferrites strongly prefer the hexangular axis way, which is the c-axis.

Within the grain boundaries of ferrimagnetic atoms, the spheres are aligned in two waies opposing when there is no magnetic field applied. As the magnetic field is applied and strength of applied field ( H ) increases, the magnetic minute of ferrimagnetic stuff become aligns with H. The magnetic spheres with aligned magnetic minute grow at disbursal of ill aligned 1s. In the terminal, the magnetic spheres become individual sphere when the applied magnetic field additions until a point. Single magnetic sphere is desirable as it is easy to revolve the atoms for use. Single sphere besides gives higher magnetic initiation because there are no oppose magnetic sphere, the individual sphere align in one way merely. These belongingss are ideal for doing of lasting magnet. To a higher opportunity of obtaining individual sphere in atoms of a compound, the compound frequently produced in nanoparticles. Nanoparticles tend to give few magnetic spheres, likely individual sphere. This is due to the really little size of atoms tend to give the smallest sum of grain boundary, hence the opportunity of acquiring magnetic spheres in opposite way is little comparison to the big size atoms which have more grain boundaries. Therefore in this survey, sol-gel technique which is able to bring forth nano-sized atoms was employed.

The magnetic belongingss of the hexangular Sr ferrites are strongly dependent upon the synthesis conditions and the site penchant of the substituted cations among the five different Fe3+ sublattices viz. , tetrahedral ( 4f1 ) , rhombohedral bipyramidal ( 2b ) and octahedral ( 12k, 2a and 4f2 ) of hexangular construction [ 13 ] .

Mass susceptibleness is the ratio of the strength of magnetic attraction induced in the sample to the magnetizing field applied in response to the denseness of the substance. In commercial application, the mass susceptibleness is desirable as holding high value, for the use of strong lasting magnet and entering media.

For the composing where x = 0.2, the substituted Sr ferrite recorded lessening in mass susceptibleness. The magnetic belongingss were non every bit desirable as the value of susceptibleness demands to be comparatively high.

In the specimen with x = 0.4, a dramatically addition in mass susceptibleness was measured. The addition in susceptibleness indicated that the permutation of Co ( II ) -Ti ( IV ) had filled up the minor I?-sublattice ( spin-down ) of the magnetoplumbite construction and therefore enhanced the measured magnetization along the I±-sublattice ( spin-up ) axis.

In the specimen with x = 0.6, the mass susceptibleness decreased. The big lessening of susceptibleness indicated that at this ratio, the Co ( II ) -Ti ( IV ) cations may good hold occupied the cation sites which were in the I±-sublattice ( spin-up ) .

For x = 0.8 to 5.0, it was found that both specimens recorded similar values of susceptibleness. As the permutation of Co ( II ) -Ti ( IV ) increased, the susceptibleness showed a rapid lessening. It might hence be expected that farther permutation will later bring forth a superparamagnetic-like Sr ferrite. Superparamagnetism is a phenomenon by which magnetic stuffs may exhibit a behaviour similar to paramagnetism at temperatures below the Curie temperature.

For x = 6.0 shows negative value of mass susceptibleness, indicates the formation of Co oxide and Ti dioxide which are diamagnetic. There are no Fe oxides which gives ferromagnetic belongingss.

From the old published survey, the partial permutation of Fe3+ ions with a Co2+ + Ti4+ brace was attempted [ 4 ] . However, the coercive force reduces and at the same time impregnation magnetisation besides reduces. Therefore, the ratio of substituted cations is really of import in modifying the magnetic belongingss of ferrite.

Single sphere atoms of Ti-Co substituted M-type hexaferrite posses attractive belongingss for the recording media applications [ 13 ] . Such permutations at Fe site are effectual in cut downing the coercivity and magnetocrystalline anisotropy but require higher annealing temperature for the individual stage formation. It has besides been reported that when synthesising Ti-Co substituted hexaferrites, it is hard to avoid the formation of Co ferrite. Although the coercivity lessening by the permutation of Co-Ni but at the same clip the impregnation magnetisation of the stuffs lessening which limit their applications in the high denseness entering media.

Chapter 4: Decisions

4.1 Decisions

4.2 Future Work

4.1 Decision

The consequence of cation permutation on magnetic belongingss of Sr ferrite is discussed in the old chapter. The magnetic belongingss are differing matching to the different cation permutation ratios. There existed important tendency which corresponded to the alterations in permutation ratio in Sr ferrite. The mass susceptibleness is the highest at x = 0.4 in SrCoxTixFe12-2xO19. This indicates that this cation permutation ratio gives best magnetic behavior where the magnetisation is the highest. This phenomenon is favorable for commercial application such as doing of lasting magnet and magnetic recording media.

4.2 FUTURE WORK

In this survey, the magnetic belongingss of M-type hexangular SrFe12O19 and cation substituted SrFe12O19 was studied. One of the magnetic belongingss, mass susceptibleness of the ferrites was determined in this survey, by utilizing magnetic susceptibleness balance. Besides magnetic susceptibleness balance, the survey on magnetic belongingss can be improved by utilizing SQUID gaussmeter or vibrating sample gaussmeter ( VSM ) [ 12 ] to look into the impregnation magnetization, remnant magnetization and coercivity. These three magnetic belongingss are the indispensable one to find their magnetic behavior for assorted applications. However, these two instruments are non available in our research lab.

The cobalt-titanium permutation is replacing the Fe sites alternatively of Sr sites. The Sr site could be substituted with other passage elements or rare earth elements with the similar atomic radii, illustration for Bi and rare earth.

In future, farther survey could be carried out by substituted rare earth wholly to replace strontium ferrite to look into whether the M-type hexangular construction remains.

One of the ways to heighten magnetic belongingss is to bring forth individual sphere atoms by partner offing the divalent-tetravalent permutation in Sr ferrite with appropriate man-made methods. Besides cation permutation by Co2+-Ti4+ brace, sol gel derived strontium ferrite with Fe substituted by Zn2+ , Ti4+ and Ir4+ have been carried out [ 9 ] . They are Zn2+-Ti4+ brace and Zn2+-Ir4+ brace. If this is true, it will hold a great impact on the engineering of tomorrow.