University of Dhaka, Bangladesh Effect of dopants on the electromagnetic properties of Ni-Cu-Zn Ferrites Submitted by S.M.Maksud-Ul-Alam Exam Roll no. 3710 Session-2006-2007 Registration no.: HA-34096 Department of Physics University of Dhaka, Bangladesh Jun 2010

Objectives of the research work Prepare series of Ni-Cu-Zn ferrite doped with CoO , Bi2O3 and Pbo by standard ceramic double sintering method. Determine optimum sintering temperature by sintering the samples over wide range of temperature. Decrease magnetic losses with optimum permeability. Determination of ferromagnetic to paramagnetic transition temperature, TC Determination of phases, structure, density, resistivity of the samples. Correlate magnetic properties with appropriate composition and sintering temperature.

Ni-Cu-Zn Ferrites demands… Ferrimagnetic cubic spinel ferrites demanded characteristics that make them technologically very useful are: Used widely as high frequency ferrite because of their high electrical resistivity and high permeability in RF region. Sufficiently low losses over wide range of frequencies. High dielectric constant that makes them useful for microwave applications. High mechanical hardness and environmental stability. Low cost. Exact mechanical dimensions. Large number of controllable parameters.

Performances…… Ferrites are used today in radio and television, microwaves and satellite communications, audio, video and digital recording and as permanent magnets They have been also used in high quality filters, inductor and transformer cores, humidity sensors. The recent application, such as multilayer chip inductors, are currently used in notebook computers, hard disk drivers as memory core and other electronic products. Widely used in Noise Suppression such as suppression of Electromagnetic Interferences to audio system. Also perform as Deflection Yokes for CRT & Video Displays.

Methodology of Ferrite Preparation Table 01: Composition of Ni0.27Cu0.15Zn0.58Fe2O4 ferrites. Zn content, x Weight% of CoO (5mol%) Weight% of Bi2O3 (0.5mol%) Weight% of PbO 0.15 1.68 0.97 0.5 Sample identification Table 02: Sample identification according to the substitutional doping level. Ni0.27Cu0.15Zn0.58Fe2O4 Ni0.27Cu0.15Zn0.58Fe2O4 doped with 5mol% CoO doped with 0.5mol% Bi2O3 doped with 0.5mol% PbO Sample01 Sample02 Sample03 Sample04

Weighing by different mole percentage Oxide of raw materials Weighing by different mole percentage Wet mixing by ball milling Dry mixing by agate mortar Drying Briqueting Milling Pre-sintering Pressing to desired shapes Sintering Finished Product

Effect of Sintering Temperature Sintering temperature has a great influence on the magnetic and electrical properties of polycrystalline ferrites such as: Density significantly increases with the increase of sintering temperature. Sintering temperature activates the grain growth of the microstructure. Initial permeability increases with both the increase of density and grain size of the ferrites. Therefore optimization of the sintering temperature corresponding to desire properties is very crucial in ferrite processing.

Effect of Additives… The proper selection of additives /substitution have enormous influence on the properties of ferrites: Change Curie temperature Affect density/porosity Reviews sintering temperature Change resistivity/ dielectric properties

T0C 10000C 3h 2h 13min (1800C/h) 3h (2000C/h) Room Temperature 6000C Furnace cooling 1h 30min (2000C/h) 7000C Time (h) HEATING Cycle Fig 01: Heating cycle of sintering the samples at 1000°C. T0C 10500C 3h 2h 30min (1800C/h) 3h (2000C/h) Room Temperature Furnace cooling 1h 45min (2000C/h) 7000C Time (h) Fig 02: Heating cycle of sintering the samples at 1050°C.

T0C 11000C 3h 2h 46min (1800C/h) 3h (2000C/h) Room Temperature Furnace cooling 2h (2000C/h) 7000C Time (h) HEATING Cycle Fig 03: Heating cycle of sintering the samples at 1100°C. T0C 11500C 3h 3h 3min (1800C/h) 3h (2000C/h) Room Temperature 6000C Furnace cooling 2h 15min (2000C/h) 7000C Time (h) Fig 04: Heating cycle of sintering the samples at 1150°C.

HEATING Cycle T0C 12000C 3h 3h 20min (1800C/h) 3h (2000C/h) Room Temperature Furnace cooling 2h 30min (2000C/h) 7000C Time (h) Fig 05: Heating cycle of sintering the samples at 1200°C.

Sintering Temperature, RESULTS AND DISCUSSION Density Table 03: Variation of bulk density of the samples with sintering temperature Set Sintering Temperature, TS/3h, (0C) Bulk Density, db (gm/cc) Ni0.27Cu0.15Zn0.58Fe2O4 (Sample01) 1100 4.44 1200 4.95 Ni0.27Cu0.15Zn0.58Fe2O4+ CoO (Sample02) 4.96 Ni0.27Cu0.15Zn0.58Fe2O4+ Bi2O3 (Sample03) 1150 4.94 4.93 Ni0.27Cu0.15Zn0.58Fe2O4+ PbO (Sample04) 4.55 5.08

XRD Fig 06: X-ray Diffraction (XRD) pattern of the of Ni0.27Cu0.15Zn0.58Fe2O4, doped with CoO, Bi2O3 and PbO.

Lattice Parameter Set Lattice Parameter, a0 (Å) Sintering temperature: 12000C/3h Table 04: Lattice parameter, theoretical density and bulk density of the samples sintered at 1200°C/3h. Set Lattice Parameter, a0 (Å) X-ray density, dx (gm/cc) Bulk Density, db (gm/cc) Ni0.27Cu0.15Zn0.58Fe2O4 (Sample01) 8.433 5.29 4.95 Ni0.27Cu0.15Zn0.58Fe2O4+ CoO (Sample02) 8.408 5.43 4.92 Ni0.27Cu0.15Zn0.58Fe2O4+ Bi2O3 (Sample03) 8.405 5.4 4.93 Ni0.27Cu0.15Zn0.58Fe2O4+ PbO (Sample04) 8.404 5.37 5.08

Curie temperature Sintering temperature: 12000C/3h Fig 07: Curie temperature of Ni0.27Cu0.15Zn0.58Fe2O4 Fig 08: Curie temperature of Ni0.27Cu0.15Zn0.58Fe2O4 doped with CoO (5mol%)

Sintering temperature: 12000C/3h Fig 09: Curie temperature of Ni0.27Cu0.15Zn0.58Fe2O4 doped with BI2O3 (0.5mol%) Fig 10:Curie temperature of Ni0.27Cu0.15Zn0.58Fe2O4 doped with PbO (0.5mol%)

TC SUMMERY Sample Curie Temperature,TC0C Ni0.27Cu0.15Zn0.58Fe2O4 Sintering temperature: 12000C/3h TC SUMMERY Sample Curie Temperature,TC0C Ni0.27Cu0.15Zn0.58Fe2O4 (Sample01) 160 Sample02: doped with CoO 177 Sample03: doped with Bi2O3 161 Sample04: doped with PbO 156

CoO, Bi2O3 and PbO, sintered at 1200°C/3h. Sintering temperature: 12000C/3h Permeability ln f Fig 11: Complex Permeability (μ’) vs Frequency Ni0.27Cu0.15 Zn0.58 Fe2O4 doped with CoO, Bi2O3 and PbO, sintered at 1200°C/3h.

Frequency dependence Permeability at different sintering temperature Sample02: doped with CoO Sample01: Ni0.27Cu0.15Zn0.58Fe2O4

Frequency dependence Permeability at different sintering temperature Sample03: doped with Bi2O3 Sample04: doped with PbO

Density Resistivity Sample Resistivity, ρ (Ω-m) Sintering temperature: 12000C/3h Table 06: Room temperature resistivity for the samples sintered at 12000C for 3hours. Sample Resistivity, ρ (Ω-m) Ni0.27Cu0.15Zn0.58Fe2O4 (Sample01) 99.02 Sample02: doped with CoO 24.24 Sample03: doped with Bi2O3 1044 Sample04: doped with PbO 41.13

This is the behavior of semiconductor. Fig 12: Temperature Vs Resistivity at 100kHz From Fig, the value of Resistivity decreases with increasing temperature. This is the behavior of semiconductor.

Dielectric constant Temperature dependence Dielectric Constant Sintering temperature: 12000C/3h Fig 13:Temperature dependent Permittivity, є’ at 100kHz Fig 14:Temperature dependent Permittivity (img), є’’ at 100kHz

Fig 15:Frequency dependent Permittivity, є’ for sample01 Frequency dependence Dielectric Constant at different sintering temperature Fig 15:Frequency dependent Permittivity, є’ for sample01 Fig 16:Frequency dependent Permittivity, є’ for sample02

Fig 17:Frequency dependent Permittivity, є’ for sample03 Frequency dependence Dielectric Constant at different sintering temperature Fig 17:Frequency dependent Permittivity, є’ for sample03 Fig 18:Frequency dependent Permittivity, є’ for sample03

Conclusion The samples are characterized by X-ray Diffraction which confirmed the single phase cubic spinel structure 2. It was observed that the lattice parameter changes slightly when dopants were added. The lattice parameter of pure and doped with Co, Bi and Pb are 8.433, 8.408, 8.405, 8.4024 and 8.404 Ǻ respectively. 3. Curie temperatures of pure(Ni0.27Cu0.15Zn0.58Fe2O4) and doped with Co, Bi and Pb are 160°C, 177°C, 161°C and 156°C respectively. The difference between the peak value of real and imaginary part was observed at ± 3°C, which is very much appreciated. 4. For all the samples, permeability increases with increasing sintering temperature which is connected with the increased density and grain size. 5. The highest value of resistivity was obtained for Bi2O3 doped sample which is 1044Ω-m. Resistivity decreases with increasing sintering temperature. This may be related to the decrease of porosity. 6.The dielectric constant decreases with increasing frequency, which confirms the dielectric behaviour of the ferrite materials. The temperature dependence of dielectric constant shows that the dielectric constant increases with increasing temperature, which is a normal dielectric behaviour, observed in most of the ferrite materials.

Prof. Shamima Karim Choudhury University of Dhaka. Special thanks to my supervisor Prof. Shamima Karim Choudhury University of Dhaka.

Thank you. Have a nice day.