Sains Ma1aysiana 26(3&4): 87-98 (1997)                                                                     Sains Fizis dan Gunaan/

                                                                                                                                      Physical and Applied Sciences

The A.C. Electrical Response from the Grain

and Grain Boundary Components of a

Li_0.25Ni_0.2Zn_0.3Fe_2.25O₄ Ferrite

Ahmad Nazlim Yusoff & Mustaffa Hj. Abdullah

Jabatan Fizik

Fakulti Sains Fizis dan Gunaan

Universiti Kebangsaan Malaysia

43600 UKM Bangi Selangor D.E. MALAYSIA

ABSTRACT

The a.c. electrical response of a polycrystalline Li_0.25Ni_0.2Zn_0.3Fe_2.25O₄ ferrite is studied by means of impedance spectroscopy. The impedance measurement was performed at different input voltage amplitudes in ten decades of frequency (1 mHz - 10 MHz). Two overlapping semicircles with negative capacitance phenomenon below 1 Hz are observed at all amplitudes. The two semicircles are mainly attributed to the grain and grain boundary processes at high and low frequencies respectively. The grain boundary impedance shows a non-linear dependence on the input voltage, where the corresponding impedance semicircle is smaller for larger amplitude. However, a linear response is observed for the grain component. The dependence of the a.c. electrical properties of the grain and grain boundary components on the amplitude of the input voltage is discussed.

ABSTRAK

Ransangan elektrik a.u. daripada ferit Li_0.25Ni_0.2Zn_0.3Fe_2.25O₄ berpolihablur dikaji dengan menggunakan spektroskopi impedans. Pengukuran impedans dilakukan pada beberapa amplitud voltan masukan dalam julat sepuluh dekad frekuensi (1 mHz - 10 MHz). Dua lengkung separuh bulatan yang bertindih dengan fenomena kapasitans negatif di bawah frekuensi 1 Hz dapat diperhatikan pada setiap nilai amplitud. Kedua-dua lengkung separuh bulatan tersebut berpunca daripada proses-proses butiran dan sempadan butiran masing-masing pada frekuensi tinggi dan rendah. Impedans sempadan butiran menunjukkan persandaran tak-linear ke atas voltan masukan, dengan separuh bulatan impedans yang berpadanan yang mengecil dengan peningkatan amplitud. Akan tetapi, suatu ransangan linear dapat diperhatikan bagi komponen butiran. Kebergantungan sifat elektrik a.u. bagi komponen-­komponen butiran dan sempadan butiran kepada amplitud voltan masukan dibincangkan.

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Yusoff, A. N. & Abdullah, M. H. 1997. Impedance and dielectric properties of an Mn-Zn ferrite. To appear in J. Phys. Sci. 8: 15-112.