Name:  Ahmed yousef abdel Haseib Ahmed       

Date of Birth:  12/ 11/ 1964

Nationality:  Egyption

Previous Degrees:  B.Sc Science

Registration Date:  July- 2003

Awarding Date:  25/12/2007

Supervisors:

1- Prof. Dr. Mohamed Ali Ahmed

2- Prof. Dr. Abou Bakr Abdel Moneim Ramadan

3- Dr. Mona Kmaal Ouf

Examiners:

1- Prof. Dr. Tetuaki  NISHIDA

2- Prof. Dr. Mabrouk Kamal El-Mansy

3- Prof. Dr.Mohamed Ali Ahmed

Title of Thesis:

Effect of preparation Conditions and Gamma Irradiation on the Electrical Properties of Cu-Zn Rare Earth Ferrite.

Key Words:

( Cu-Zn Ferrite – Electrical Properties – Gamma Irradiation)

Summary:

All the investigated samples are prepared using standard ceramic technique. The samples has the general formula Cu_1-xZn_xR_yFe_2-yO₄ where x and y are variables and R is rare earth element = ( La, Sm, Gd and Dy). X-ray diffraction analysis carried out and the electrical properties ( e', e'' and s ) of the prepared samples were measured at different temperatures as a function of the applied frequency ranging from 100kHz

up to 5MHz. The samples classified into four different groups the variation of ( e', e'' and s ), the results reveal a decrease in the dielectric constant e' with increasing frequency for all samples due to hopping of electrons between Fe²⁺ and Fe³⁺ with jump frequency smaller than the applied frequency. Also e'' increase with increasing temperature due to the decrease in the friction between the dipoles as well as the thermal energy dissipation inside the sample. The Ac conductivity increases with increasing temperature giving raise of three regions. The data show that ( e', e'' and s ) increases with increasing La3+ ion content. More than one polarization mechanism was expected to take place in cu-Zn doped La depending on the range of temperature and frequency. The samples of chemical formula Cu_0.5Zn_0.5La_0.35Fe_1.65O₄ were irradiated by ⁶⁰Co Gamma source with accumulated doses from 10 up to 100Mrad. The results were interpreted in view of increasing the electron hopping. The increase in the e' of the samples after irradiation is attributed to the transferring of Fe3+ ions from A site to B site after to Fe²⁺. This means that the irradiation reduces the resistance of sample ( i.e more charge carriers are generated by g- irradiation owing to the following:

Cu¹⁺ + g Û Cu²⁺ + e^-                                                               

Fe²⁺ + g Û Fe³⁺ + e^-                                                     

Also it was found that seebeck coefficient has negative values after Gamma irradiation. This was contributed to negative charge carriers initiated due to Gamma irradiation.

 

 

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