Laser induced structural and transport properties change ... - CiteSeerX

J Mater Sci (2007) 42:4098–4109 DOI 10.1007/s10853-006-1151-z

Laser induced structural and transport properties change in Cu–Zn ferrites M. A. Ahmed Æ A. A. I. Khalil Æ S. Solyman

Received: 18 May 2006 / Accepted: 16 October 2006 / Published online: 17 February 2007 Springer Science+Business Media, LLC 2007

Abstract The samples were prepared from analar oxides (BDH) using the standard double sintering ceramic technique. X-ray diffraction (XRD) was carried out to assure the formation of the sample in single spinel phase. The effect of Q-switched Nd:YAG laser irradiation with wavelength of 1064 nm on the electrical properties of the prepared samples Cu1 – x Znx Fe2O4 (0.1 £ x £ 0.6) was discussed. The temperature dependence of the polarization and a.c. conductivity was studied in the range (300 K £ T £ 700 K) at different applied frequencies (10 kHz £ f £ 4 MHz). The activation energies were calculated at different temperature regions for the unirradiated and irradiated samples. Their values indicate the semi-conducting like behaviour of the sample. Comparison between the ac electrical conductivity, dielectric constant, dielectric loss, for unirradiated and irradiated samples with different Zn concentrations (0.1 £ x £ 0.6) was performed. Seebeck voltage measurements showed that, the n and p-type conduction act in cooperation with each other. The change in a.c. conductivity is attributed to the creation of lattice vacancies after laser irradiation. The decrease of the a.c. conductivity and the M. A. Ahmed (&) Materials Science Lab.(1), Physics Department, Faculty of Science, Cairo University, Giza, Egypt e-mail: [email protected] A. A. I. Khalil Laser Industrial Applications Department, National Institute of Laser Enhanced Science (NILES), Cairo University, Giza, Egypt S. Solyman Physics Department, Faculty of Science, Zagazig University, Zagazig, Egypt

123

dielectric constant after laser irradiation with 18000 shots may be due to formation of traps, which decrease the number of carriers. The lattice mismatch in the grain boundaries causes a planar array of localized states, being able to capture free carriers. The accumulated charge constitutes an electrostatic barrier impeding carriers from free motion. Thus, it is possible to optimize the conductivity of this type of ferrite material to be used in technological applications at room temperature.

Introduction Ferrites have many important applications in industry, modern telecommunication and electronic devices and they are still of interest as promising materials for miniature electro-optic modulators, pyroelectric detectors, piezoelectric sensors, high quality filters, transformer cores, ferrite isolators, memory core industry, multilayer chip inductor, rod antennas, radio frequency circuits [1–5], wave guides and electronic memory elements as well as a recording media. For these reasons, engineers and scientists are keenly interested in determining their characterization [6, 7]. The electrical properties of ferrite materials have been found to alter, depending on the substitution of different valance cations as well as the preparation conditions. Moreover, the dielectric constant (e¢), ac electrical conductivity (ra.c.) and permeability of semiconductor ferrites are very sensitive to the chemical composition and industrial applications. Cu0.5Zn0.5Fe2O4 nanocrystallites powder (average

J Mater Sci (2007) 42:4098–4109

Effect of laser irradiation on the structure of Cu1 – x Znx Fe2O4 (0.1 £ x £ 0.6) ferrites Figure 1 shows the XRD patterns of Cu1 – xZnxFe2O4 (x = 0.5) as a typical one before and after laser irradiation. From X-ray analysis, it is observed that the samples crystallize in a single-phase spinel structure of cubic symmetry as compared with ICDD card number [25-0283] [14, 15]. After laser irradiation, the diffractogram indicates the formation of a distorted cubic structure. This is because laser interacts with the metal ions on A and B sites, Thus a more contribution towards conductivity by generation of Fe2+ and Cu1+ from Fe3+ and Cu2+ takes place. As a result of the

(311)

3500

Cu0.5Zn0.5Fe2O4

3000

2000

(511)

(222)

1000

( 400 )

1500

(440)

Before laser After laser

2500

(220)

The samples Cu1 – xZnxFe2O4 (0.1 £ x £ 0.6) were prepared using the double sintering ceramic technique from pure analar oxides CuO, ZnO and (Fe2O3) [11]. Grinding were carried for 3 h after mixing in molar ratios to give the composition Cu1 – x Znx Fe2O4 (0.1 £ x £ 0.6) and then pressed in pellet form using uniaxial press of pressure 8 · 105 N/m2. The samples in the form of disks were pre-sintered at 850 C for 10 h with heating rate of 2 C min–1. The final sintering was carried out at 1150 C for 10 h and then cooled to room temperature with the same rate as that of heating. The pre and final sintering were carried out using a UAF 16/5 (UK) furnace with microprocessors to control both heating and cooling rates. The samples were smoothly polished to have uniform parallel surfaces (2 cm in diameter and 0.2 cm in thickness), coated with a thin layer of silver paste as contact electrodes for electrical properties measurements. The samples were placed between two electrodes in an evacuated cell of silica tube supported with a furnace. The temperature of the samples was measured and controlled using Chromel–Alumel thermocouple attached to the samples.

Results and discussion

( 11 1)

Experimental techniques

X-ray diffraction (XRD) patterns were performed using a Philips PW1730 X-ray unit with CoKa radiation to assure the good preparations. The real part of the dielectric constant and ac conductivity were recorded at different temperatures as a function of frequency (1 kHz–4 MHz) using RLC bridge model HP (USA) self calibrated. For laser irradiation study, the samples were irradiated by Nd:YAG laser. The laser was operated at a wavelength 1064 nm using repetition rate of 10 Hz. The average power is measured to be of the order 5 W and pulse duration time of 10 ns. The exposure time was 30 min. The resonance frequency and antiresonance were carried out by the method described in previous work [12, 13].

Intensity (Arbitrary Unit)

size 13 nm) were synthesized from Cu–Zn spent catalyst (fertilizers) industries. The parameters affecting the magnetic properties and crystallite size of the produced ferrites powder were systemically studied by different authors [8, 9]. Spinel copper ferrite shows a remarkable variation in its atomic arrangement depending critically on the thermal history of the preparation and it may be attributed to the distribution of Cu and Fe cations between the two nonequivalent lattice A and B sites [10]. It has been pointed out that the distribution and the valance of metal cations on these sites determine the magnetic and electrical properties. The major goal of the present work is to investigate the effect of the laser irradiation, temperature and frequency on the e¢, e¢¢, ra.c. and Seebeck coefficient of Cu–Zn ferrite. This will open a new era for using laser irradiation in optimizing the electrical properties of the investigated samples to be more applicable. The real part of the dielectric constant e¢ as well as the ac conductivity of the rare earth ferrite Cu1 – x Znx Fe2O4 (0.1 £ x £ 0.6) was measured at different temperatures (300–800 K) as a function of frequency (10 kHz– 4 MHz). More than one hump was obtained due to the presence of different polarization processes and conduction mechanisms.

4099

500 0 20

30

40

50

60

70

80

2θ°

Fig. 1 X-ray diffraction patterns of Cu0.5 Zn0.5 Fe2O4 before and after laser irradiation

123

4100

larger ionic radius of Fe2+ and Cu1+ than that of Fe3+ and Cu2+, respectively a small distortion of the spinel cubic structure is obtained. Moreover, lattice vacancies generated after laser irradiation contribute to the structural deformation. Effect of laser irradiation on the electrical conductivity of Cu1–xZnxFe2O4 (0.1 £ x £ 0.6) ferrites The effect of laser irradiation on the investigated samples gives rise to the production of lattice defects as the result of the displacement of atoms from their equilibrium position. The displaced ions are expected to occupy the lattice vacancies and hence reduce oxygen ions diffusion. The laser irradiation of the samples alters the electrical conductivity as the result of absorbing dose in the material. Figure 2: a–l illustrates the temperature dependence of the a.c. conductivity for unirradiated and irradiated samples of (Cu1 – xZnxFe2O4) by using Nd:YAG laser of 15 min exposure time for each face of the samples in the frequency range (1 kHz–4 MHz). It is noticed that the a.c. conductivity for irradiated samples increases exponentially with temperature at fixed frequency range (10–4000 kHz), i.e. dra.c./dT is positive. The increase of the a.c. conductivity with temperature is attributed to enhancement of the Verwey hopping mechanism between Fe2+ M Fe3+ + e– and hole hopping between Cu2+ + e- M Cu1+ on the B sites, where most of Cu2+ ions prefer to occupy B sites together with Fe3+ ions. The a.c. conductivity with rising temperature was previously studied [16]. The effect of laser irradiation on the electrical conductivity for the samples Cu1 – xZnxFe2O4 (0.1 £ x £ 0.6) is clarified in Fig. 2: a–l. From the figure, it is noticed that the a.c. conductivity increases with increasing both temperature and frequency for the unirradiated and irradiated samples. Comparing the conductivity before and after irradiation, it is clear that the values of the a.c. conductivity decrease after irradiation at all frequencies and temperature. This is due to trapping of charge carriers in the vacancies, which were created as a result of laser irradiation. The increase in a.c. conductivity with increasing frequency is an acceptable result because the frequency acts as a pumping force pushing the charge carriers from one conduction state to another, especially at low frequency. The applied frequency in the present work is low frequency and 4 MHz is the highest of the lowest frequency region. This behaviour

123

J Mater Sci (2007) 42:4098–4109

is the general trend of Cu substituted ferrites, where the most predominant conduction mechanism is that of Verwey [17] in which the electron hopping takes place between ions of different valences in the equivalent lattice site. This result is in agreement with that published by other authors [18, 19]. It is well known that, the irradiation by laser shock waves is followed by the formation of point defects and some of these vacancies could react with donor impurities, which reduce relatively the concentration of electrically active donors in the sample [19]. At high frequency, 4 MHz, the a.c. conductivity is decreased at high temperature for unirradiated samples as shown in Fig. 2: a–k. From the experimental data, the calculated values of the activation energies are plotted against the frequency in the low temperature range (335–665 K) Fig. 3. It is noted that the decrease in the activation energy with increasing frequency is an acceptable trend as a result of increasing hopping probability as well as conductivity. The increase in the activation energy after laser irradiation at lower frequencies is the result of initiating defects in the samples, which decreases the conductivity. The decrease of activation energy after laser irradiation at higher frequency may be due to either creating of small polarons or initiating holes from varying the valence of Cu ions. Effect of laser irradiation on the dielectric constant and dielectric loss of Cu1 – xZnxFe2O4 (0.1 £ x £ 0.6) ferrites The temperature dependence of the dielectric constant e¢ and dielectric loss e¢¢ at different frequencies from 10–4000 kHz for unirradiated and irradiated Cu1 – xZnx Fe2O4 (0.1 £ x £ 0.6) ferrites by laser with 18,000 laser shots is illustrated in Fig. 4, 5. The increase in e¢ with temperature in the range (290–430 K) can be ascribed to the thermal excitation of charge carriers. Above 450 K, the dielectric constant decreases sharply as the result of high thermal energy and the increase of lattice vibrations resulting in scattering of charge carriers. The peak position and height were varied depending on both frequency and Zn content. The shift in the position towards higher temperature with increasing the applied frequency may be due to the strong effect of the field where the dipoles can’t orient themselves in the field direction. The decrease of e¢ with increasing frequency is ascribed to the increase of the jumping frequency of the charge carriers, which gives a remarkable dispersion as in Fig. 4. The value of

J Mater Sci (2007) 42:4098–4109

4101

Fig. 2 Variation of the electrical conductivity with the reciprocal of the absolute temperature as a function of the applied frequency for Cu1 – x Znx Fe2O4; (0.1 £ x £ 0.6) before and after laser irradiation

Before Laser

0

After Laser

-4

Cu0.9 Zn0.1 Fe2 O4

Cu0.9 Zn0.1 Fe2 O4

After laser

-5

Before laser

-1

-6

-2

-1

Ln σ (σ = S.cm )

-1

Ln σ (σ = S.cm )

-7

-3

-4

-5

-6

-7

10 kHz 20 kHz 40 kHz 100 kHz 200 kHz 400 kHz 1 MHz 2 MHz 4 MHz

-8 1.5

2.0

-8

-9

-1 2


-1 3 1.0

1.5

-1 0

-1 1

2.5

3.0

3.5

-1

2.0

2.5

3.0

3.5

-1

1000/T (K )

1000/T (K ) -3

0

Cu0.8 Zn0.2 Fe2 O4

Cu0.8 Zn0.2 Fe2 O4 -4

Before laser

-1

After laser

-5

-2

-3

-1

-1

ln(σ) [Ω m ]

-1

Ln σ (σ = S.cm )

-6

-4

-5

-6

-7 1.5


2.0

-7

-8

-9

-10

-11

2.5

3.0

-12 1.0

3.5


1.5

-1

2.0

2.5

3.0

3.5

-1

1000/T (K )

1000/T (K ) -4

-1

Cu0.7 Zn0.3 Fe2 O4

Cu0.7 Zn0.3 Fe2 O4 -2

After laser

Before laser -6

-1

Ln σ (σ = S.cm )

-1

Ln σ (σ = S.cm )

-3

-4

-5

-6

-7

-8

-8

-10


-12

-9 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 -1

1000/T (K )

-14 1.0


1.5

2.0

2.5

3.o

3.5

-1

1000/T (K )

123

4102

J Mater Sci (2007) 42:4098–4109

Fig. 2 continued

-4

-4

0.5 Activation Energy (eV)

Cu0.6 Zn0.4 Fe2 O4

Before laser -6

EI EII

Cu0.6 Zn0.4 Fe2 O4

0.4

-5 0.2

-6

0.1

-7 -1

Ln σ (σ = S.cm )

-1

Ln σ (σ = S.cm )

1.0 1.5 2.0 2.5 3.0 3.5 4.0 Log f (Hz)

-8

-10 10 kHz 20 kHz 40 kHz 100 kHz 200 kHz 400 kHz 1 MHz 2 MHz 4 MHz

-12

After laser

0.3

-8

-9

-10

-11


-12

-13

-14

-14

1.0

1.2

1.6

2.0

2.4

2.8

1.5

2.0

3.0

3.5

-1

1000/T (K )

-1

1000/T (K ) -6

-2 -8

0.50

Before laser

-8

Activation Energy (eV)

-7

2.5

3.2

-9

-10

Cu0.5 Zn0.5 Fe2 O4

0.45

After laser -4

0.35 0.30 0.25

-6

0.20

1.60

1.65

1.70

1.75

500 1000150020002500 300035004000

-1

1.55

0.10 0

Frequency (kHz)

-1

Ln σ (S.cm )

-9

-11 1.50

-10

-11

-12

-13


-14 1.5

Ln σ ( σ = S.cm )

0.15

-8

-10

-12

-14


Cu0.5 Zn0.5 Fe2 O4 2.0

2.5

-16 1.0

3.0

1.5

2.0

-1

2.5

3.0

3.5

-1

1000/T (K )

1000/T (K )

-1

-4

Cu0.4 Zn0.6 Fe2 O4

Cu0.4 Zn0.6 Fe2 O4

Before laser

-2

After laser -6

Ln σ ( σ = S.cm )

-4

-1

-1

-1

ln(σ) [Ω m ]

-3

-5

-6

-7

-8

-9 1.2

123


1.6

-8

-10

-12

2.0

2.4

2.8

3.2

-14 1.0


1.5

2.0

2.5

3.0

J Mater Sci (2007) 42:4098–4109 0.6

0.5

(a)

EI (eV) Before laser EI (eV) After laser EII (eV) Before laser EIII (eV) After laser

X = 0.1

(b)

0.4 0.3 0.2

X = 0 .2

0.4


0.5


Fig. 3 Dependence of the activation energy on the applied frequency in the low (EI) and in the high (EII) for Cu1 – x ZnxFe2O4; (0.1 £ x £ 0.6) before and after laser irradiation

4103

0.1 0.0

0.3

0.2


0.1

0.0 10

100

1000

10000

10

100

log f (kHz)


X = 0. 3

0.6 0.5 0.4 0.3 0.2

(d)

0.7

Activation energy (eV)

(c)

0.7


10000

0.8

0.8

0.1

X = 0 .4

EI (eV) Before laser EI (eV) After laser EII (eV) Before laser EII (eV) After laser

0.6 0.5 0.4 0.3 0.2 0.1

0.0 10

100

1000

0.0

10000

10

100

log f (kHz)

1000

10000

log f (kHz) 1.0

1.2

(e)

X = 0. 5


(f)

0.9

X = 0. 6

0.8


1.0


1000

log f (kHz)

0.8 0.6 0.4 0.2

EI (eV) Before laser EI (eV) After laser EII (eV) Before laser EII (eV) After laser

0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

0.0 10

100

1000

log f (kHz)

e¢ decreases after laser irradiation at all temperatures. This behavior may be due to formation of point defects, which act as trapping centers for the charge carriers. Accordingly, the conductivity as well as e¢ decreased because they are of the same origin. Though, the investigated samples obey the model [20] [e¢ a r]. From a closer look to the obtained data one can observe the decrease of e¢ with increasing Zn content before and after laser irradiation. This agrees well with the data of the conductivity Fig. 2. The electrons produced from the valence exchange Fe2+ ‹ fi Fe3+ + e- are captured by the Cu ions existing on the octahedral site as follows Cu2+ + e- ‹ fi Cu1+. This in turns decreases the conductivity as well as e¢. Consequently, one can say that the conduction in the investigated samples is a collective contribution of two types of carriers; p and n-type carriers. Therefore, the position of the peak

10000

10

100

1000

10000

log f (kHz)

depends on whether the majority is in p-type or ntype carriers in the sample. It can be noticed that as the iron content is increased resulting in more Fe2+ ‹ fi Fe3+ + e- transitions. Furthermore, the increase in n-type carrier with increasing Fe content results in a shift of peak temperature towards higher temperature side with increase in frequency. Figure 5 a–l shows the temperature dependence of the dielectric loss factor e¢¢ at different frequencies (10 kHz £ f £ 4 MHz) before and after laser irradiation with 18,000 laser shots. The data clarify that the value of dielectric loss increases with increasing temperature at frequencies 10–4000 kHz, for different Zn concentrations (0.1 £ x £ 0.6), but at x = 0.2 and 0.4, the peaks will be observed at 440, 600 K respectively. The sharp decrease of e¢¢ with increasing frequency may be due to the fact that the activation energy is not sufficient to create dipoles, where the peaks are

123

4104

J Mater Sci (2007) 42:4098–4109

disappeared after laser irradiation. The data correlate the variation of lnra.c., e¢, e¢¢ versus Zn content are shown in Figs. 6–8. The Seebeck coefficient was carried out for the investigated samples Fig. 9 a–f. The positive and negative values of Seebeck coefficient, for all samples, over the investigated temperature range denote the presence of p and n-type charge carriers. The presence of the two types of charge carriers defines the two regions of temperature dependence of conductivity in which the sample is changed from p-type to n-type and vice versa. Part of the energy of the applied field frequency consumed in the orientation of the dipoles and other part of this energy enhances the electrical conductivity of the samples.

(a)

Conclusion Cu–Zn ferrites induced in wide range of industrial applications, due to their unique properties. The XRD patterns of irradiated samples by laser show a distorted cubic structure. Drop in the values of electrical conductivity; dielectric constant e¢ and dielectric loss e¢¢ at range of frequencies from 10 to 4000 kHz for irradiated ferrites samples by laser with 18,000 laser shots were detected. Response of these materials to laser irradiation showed different effects on the conductivity depending on the temperature of the samples. Three regions of conductions (300–350 K), (350– 500 K) and (500–670 K) were obtained. Both electrons and holes participate in conduction mechanism.

(c)

(b) 2000

1200 10 kHz 20 kHz 40 kHz 100 kHz 200 kHz 400 kHz 1 MHz 2 MHz 4 MHz

Before laser

1000

800

1800 1600 1400


Cu0.8 Zn0.2 Fe2 O4

After laser

8000

Before laser

7000 6000

'

'

'

400


9000

1200 600

10000

Cu0.9 Zn0.1 Fe2 O4

1000

5000

800

4000

600

3000

400

2000

200

1000

200 Cu0.9 Zn0.1 Fe 2 O4

0 250 300

0 250 300 350 400 450 500 550 600 650

350

T(K)

3000

450

500

550

0 250 300 350 400 450 500 550 600 650

600

T (K)

(d)4000 3500

400

(e) 10 kHz 20 kHz 40 kHz 100 kHz 200 kHz 400 kHz 1 MHz 2 MHz 4 MHz

T (K)

(f)


Before laser

600

600

500

Cu0.8 Zn0.2 Fe2 O4

400

'

After laser

'

'

Cu0.7 Zn0.3 Fe 2 O4


After laser

2500 2000

700

400

1500 200

1000

300 500 Cu0.7 Zn0.3 Fe2 O4

0 250

300

350

400

T(K)

450

500

550

0 250 300 350 400 450 500 550 600 650

T (K)

200 250 300 350 400 450 500 550 600

T (K)

Fig. 4 (a–l) Dependence of the dielectric constant on the absolute temperature as a function of the applied frequency for Cu1 – x Znx Fe2O4; (0.1 £ x £ 0.6); before and after laser irradiation

123

J Mater Sci (2007) 42:4098–4109

4105 40

90

Cu0.6 Zn0.4 Fe2 O4

25

' 1000

10 kHz 20 kHz 40 kHz

70

1100

30

Cu0.6 Zn0.4 Fe2 O4

80

(g)

1 MHz 2 MHz 4 MHz

35

Before laser

20

900

15

800 10

60

700

5 0 300

350

400

450

500

550

600

650

700

600

750

After laser

50

T (K)

40

'

' 1000

50

(h)


1000

Before laser

500

100 kHz 200 kHz 400 kHz

40

400

' 1000

30 0.7

20

0.6

30

300 20

200

' 1000

0.5

10

0.4

10

0.3

0.2 300

320

340

100

360

T (K)

0

0 300 350 400 450 500 550 600 650 700 750

0 300

350

400

450

500

T (K)

550

600

650

700

750

300

350

400

T (K)

450

500

550

600

T (K) 800

100000

1600 10 kHz 20 kHz 40 kHz 100 kHz 200 kHz

80000

1500

(i)

1400 1300

Before laser Cu0.5 Zn0.5 Fe2 O4


700

400 kHz 1 MHz 2 MHz 4 MHz

600

Before laser Cu0.5 Zn0.5 Fe2 O4

500

1200

(j)

After laser

1100

60000

400

'

'

'

1000 900 550

300

375

40000

800

370

500 365

700

360

200

450 355

600 20000

400

345

500 350 325

350

350

375

400

425

340 335 300

450

100 350

400

450

500

400 0 300 350 400 450 500 550 600 650 700 750

Cu0.5 Zn0.5 Fe2 O4 0

300 300 350 400 450 500 550 600 650 700 750

300

T (K)

T (K)

800

350

400

450

500

550

600

T (K)

700

(k)


Cu0.4 Zn0.6 Fe2 O4

Before laser 600

600

500


(l) After laser

'

'

400

400

300

200

200

100

Cu0.4 Zn0.6 Fe2 O4 0 300

350

400

450

T (K)

500

550

600

650

700

0 300

350

400

450

500

550

600

T (K)

Fig. 4 continued

123

4106

J Mater Sci (2007) 42:4098–4109

Fig. 5 (a–l)Dependence of the dielectric loss factor on the absolute temperature of Cu1 – x Znx Fe2O4; (0.1 £ x £ 0.6) at different frequency and Zn content before and after laser irradiation

10000


7000

6000

(a)

9000

8000

7000

5000

6000

4000

ε"

ε"

Cu0.9 Zn0.1 Fe2 O4

Before laser

5000

(b)


Cu0.9 Zn0.1 Fe2 O4 After laser

4000 3000

3000 2000

2000 1000

1000

0 250

300

350

400

450

500

550

0 280

600

320

360

400

T (K)

480

520

560

30000


40000

35000

(c) 25000

30000

20000

Cu0.8 Zn0.2 Fe2 O4 25000


(d)

Cu0.8 Zn0.2 Fe2 O4

Before laser

ε"

ε"

440

T (K)

15000

After laser

20000

15000

10000

10000

5000 5000

0 250

300

350

400

450

500

0 280

550

320

360

T (K) 6000

5000

4000

3600

3200

2800

ε"

ε"

440

480

4000

(e)


Cu0.7 Zn0.3 Fe2 O 3000

400

T (K)

2400

Before laser 2000


(f)

Cu0.7 Zn0.3 Fe2 O4

After laser

1600

2000 1200

800

1000

400

0 280

320

360

400

440

480

T (K)

123

520

560

600

640

0 300

400

500

T (K)

600

J Mater Sci (2007) 42:4098–4109

4107 240

2500 10kHz 20kHz 40kHz 100 kHz 200kHz 400 kHz

2000

Cu0.6 Zn0.4 Fe2 O4

1MHz 2MHz 4MHz

220 200

Before laser

3000

Cu0.6Zn0.4Fe2O4

Before laser

2500

180

(g)

160

(h)

2000

140

Cu0.6 Zn0.4 Fe2 O4

120

After laser

ε''

ε"*1000

ε"*1000

1500


1500

100

1000

1.25

80

1000

1.00

0.75

ε" *1000

60

0.50

500

40

500

0.25

20

0.00

300 320 340 360 380 400 420 440 460 480 500 520

T(K)

0 300 350 400 450 500 550 600 650 700 750

0 300 350 400 450 500 550 600 650 700 750

T (K)

0 280

140000

600

4000

500

ε''

(i)

ε''

ε''

Cu0.5 Zn0.5Fe2 O4

Before laser

120000

100000

3000

400

440

480

520

560


Cu0.5 Zn0.5 Fe2 O4

After laser

(j)

80000 300

225

50

2000

200 40

175 150

40000

400

5000 400Hkz 1 HMz 2 HMz 4 HMz

Before laser

60000

360

T (K)

700 10 kHz 20 kHz Cu0.5Zn0.5Fe2 O 4 40 kHz 100 kHz 200 kHz

160000

320

T (K)

200

125

30

100

1000

75

20000

0

25 300

20 300

100

50

350

400

450

350

400

450

500

0

300 350 400 450 500 550 600 650 700 750

0 280

300 350 400 450 500 550 600 650 700 750

T (K)

T (K)

320

360

400

440

480

520

560

600

T (K)

1000

6000

Cu0.4 Zn0.6 Fe2 O4

Cu0.4 Zn0.6 Fe2 O4

(k)

800

700

ε''

4000

(l)

900


5000

ε''

500

600


After laser

Before laser 3000

500

400

2000 300

200

1000

100

0 300

350

400

450

500

T (K)

550

600

650

700

0 320

360

400

440

480

520

560

600

T (K)

Fig. 5 continued

123

4108

J Mater Sci (2007) 42:4098–4109 0.0020

-2

0.0015

At constant 400 K and 400 kHz

0.0010 -1

∆v/∆T (VK )

-3


-4 -5

0.0005 0.0000

Cu0.9 Zn0.1 Fe2 O4

0.0005 0.0010 - 0.0015 - 0.0020

-6

- 0.0025 250

300

350

400

450

ln σ

-7

500

550

600

650

700

T (K) 5.0E-04

-8 -1

DV/DT(VK )

0.0E+00

-9 -10

300

350

400

450

500

550

600

650

700

-5.0E-04 -1.0E-03

Cu0.8 Zn0.2 Fe2 O4

-1.5E-03 -2.0E-03 -2.5E-03

-11

-3.0E-03

-12 0.0

T'(K)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

5.0E-04

Zn content (x)

3.0E-04

-1

DV/DT(VK )

4.0E-04

Fig. 6 Variation of ln ra.c. as a function of Zn content for the samples Cu1 – x Znx Fe2O4; (0.1 £ x £ 0.6) at 400 K and 400 kHz before and after laser irradiation

2.0E-04

Cu0.7 Zn0.3 Fe2 O4

1.0E-04 0.0E+00

300

350

400

450

500

550

600

650

700

-1.0E-04 -2.0E-04 -3.0E-04

T'(K) 1. 0 E - 0 3 5. 0 E - 0 4

460 -1

440

DV/DT(VK )

At constant 400 K and 400 kHz Before laser After laser

420

ε'

400

0. 0E + 0 0 300

400

350

450

500

550

600

650

700

Cu0.6 Zn0.4 Fe2 O4

-5 . 0 E - 0 4

-1 . 0 E - 0 3

380

-1 . 5 E - 0 3

360

-2 . 0 E - 0 3

T'(K)

340 1.0E-03 5.0E-04

320 -1

DV/DT(VK )

0.0E+00

300 280 260

350

300

400

450

-5.0E-04

500

550

600

650

700

Cu0.5 Zn0.5 Fe2 O4

-1.0E-03 -1.5E-03 -2.0E-03 -2.5E-03 -3.0E-03

240 0.0

-3.5E-03

0.1

0.2

0.3

0.4

0.5

0.6

0.7

T'(K)

Zn content (x)

2.5E-02

-1

DV/DT(VK )

2.0E-02

Fig. 7 Variation of e¢ as a function of Zn content for the samples Cu1 – x Znx Fe2O4; (0.1 £ x £ 0.6) at 400 K and 400 kHz before and after laser irradiation

1.5E-02 1.0E-02

Cu0.4 Zn0.6 Fe2 O4

5.0E-03 0.0E+00 300

350

400

450

500

550

600

650

700

750

800

-5.0E-03 -1.0E-02

Fig. 9 Seebeck coefficient for Cu1 – x Znx Fe2O4 at different Zn content before laser irradiation

References

1000

At constant 400 K and 400 kHz 800


ε''

600

400

200

0 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Zn content (x)

Fig. 8 Variation of e¢¢ as a function of Zn content for the samples Cu1 – x Znx Fe2O4; (0.1 £ x £ 0.6) at 400 K and 400 kHz before and after laser irradiation

123

1. Kulikowski J (1984) J Magn Magn Mater 41:56 2. Tellini B, Giannetti R, Robles G, Lizon-Martinez S (2006) IEEE Trans Instrum Measure 55(1):311 3. Krishnaveni T, Murthy SR, Gao F, Lu Q, Komarneni S (2006) J Mater Sci 41(5):1471 4. Vipritskii DD, Nazarov AV, Raevskii SB (2006) J Commun Technol Electronics 51(1):101 5. Kramer BA, Koulouridis S, Chen C-C, Volakis JL (2006) Antennas Wireless Propag Lett 5:32, 1536 6. Ristic M, Popvice S, Music S (1990) J Mater Sci Lett 9:872 7. Letyuk LM, Zhuravlen GI (1983) Chemistry and Technology of Ferrite. Moscow: Khimiya. p 256 (in Russian) 8. Rashad MM, Khedr MH, Abdel-Halim KS (2006) J Nanosci Nanotechnol 6(1):114 9. Bryan HMO, Levistien HZ, Scherwood RC (1966) J Appl Phys 37:1438

J Mater Sci (2007) 42:4098–4109 10. Farag ISA, Ahmed MA, Hammad SM, Moustafa AM (2001) Cryst Res Technol 36:85 11. Ahmed MA, El-Khawas EH, Bishay ST (2000) JMS Lett 19:791 12. Haeter TF, Neuhaus DP, Kolb J (1954) Acoust Soc Amer 26:696 13. Radio Engineering Standards (RES). Measurements of piezoelectric ceramics, Proc IRES 4 (1961) 1161 14. Ahmed MA (1989) Phys Stat Solidi (a) 451:567

4109 15. Darwish NZ (1994) Asian J Phys 3(2):65 16. Mousa MA, Summan AM, Ahmed MA, Badawy AM (1989) J Mater Sci 24:2478 17. Verwey EJW, Haayman PW, Romeyn FC, Van Oosterhont GW (1950) Philips Res Rep 5:173 18. Saif SS, Mounir M, Khalil AAI (1995) J Faculty Edu 22:391 19. Vasilevskaya NI, Polyaninov AV, Khvostikova VD, Yanashkevich VA, Kuzmin LS (1985) Sov Phys Sc 19(4):480 20. Ahmed MA, Ateia E, El-Dek SI (2003) Mater lett 57:4256

123