الفهرس 
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Abstract
The present work is concerned with investigation of some physical and electrical properties of mixed ferrite Mn (1-x) Cd x Fe 2 0 4 (where x = 0.,0.2,0.4,0.6 and 0.8)
The samples were prepared from pure oxides using the usual ceramic technique. The mixed oxides were pressed into disc from with diameter 13 mm under the perssure 2.5 tons /cm.
The control of resistivity in ferrities is a serious problem. There are two general approches to this problem. The first is by controlling firing temperature, and the second is by the addition of minor constituents to increase or decrease the conductivity. In this thesis, The two approaches were studied.
Firstly, to study the thermal effect, polycrystalline samples of Mn Fe 2 04 were perpared at three different sintering temperatures 1100, 1150 and 1200 C.
The x-ray analysis was studied and it was found that the formation of Mn Fe2 04 affected by the sintering temperature. The structure perfection was formed at 1150 c. The lattice parameter corresponding to this temperature was calculated and it was found to be 8.55 ± 0.01 A. also, the d.c electrical conductivity was studied. The discussion of conductivity was taken from the viewpoint of the hopping mechanixm. The effect of sintering temperature on the curie point (Tc) was explained throught the oxidation process which leads to shift the curie point towards higher temperature. the curie points are 298,329 and 359 C for 1100.1150 and 1200c, respectively.
Secondly, The effect of cadmium on physical and electrical properities of Mn Fe2 04 were studied. The x-ray diffraction eas used for indentification the crystal structure. It was found that the calculated lattice parameters (a) increases with increase of Cd content. It changed from 8.55 to 8.61 according to x increased from 0 to 0.8, respectively. Also the apearent density and theoretical density have the same behaviour.