raghasudha

2.1 Materials and Synthesis

The following chemicals with high purity are used as the starting materials for the synthesis of Zn0.5Cu0.25Ni0.25Fe2-xInxO4 nano crystalline ferrites with x = 0.0, 0.1, 0.2, 0.3 and 0.4 using Citrate-gel auto combustion method.

Ni(NO3).6H2O, Cu(NO3).6H2O, Zn(NO3).6H2O, In(NO3).9H2O, C6H8O7H2O and Fe(NO3).9H2O

Using the above starting materials the nano ferrites under investigation were synthesized by Citrate-gel auto-combustion method, the detailed procedure was reported in our earlier publication [17].

2.2 Characterization

Crystal structure was analyzed by using Rigaku X-ray diffrctometer (Rigaku Miniflex II). The morphology of prepared nano ferrites was investigated using TEM analysis. Thermal properties of the samples were carried out by Thermo gravemetric analysis (TG) and Differential thermal analysis (DTA) in air and Nitrogen atmosphere. The temperature dependence magnetization measurements were carried out using Vibrating Sample Magnetometer (VSM). To investigate the temperature dependence of magnetization, two types of magnetization measurements were carried out viz. Field cooled (FC) and Zero-field cooled (ZFC) magnetization. In ZFC measurement, the ferrite sample is cooled down to the liquid helium temperature in the absence of a field and then a moderate magnetic field is applied (500 Oe) and the temperature is gradually increased simultaneously the magnetization (M) values were recorded. In FC measurement, the ferrite sample is cooled in a non-zero magnetic field and similar procedure is followed as in ZFC measurement and M values were recorded.

3. Results and Discussion

3.1 XRD analysis

X-ray powder diffraction patterns of good quality were obtained for the samples using CuKα radiation of ...

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...a peak between 500C to 2000C which can be attributed to the burning of organic matter in the sample. A rapid decline in the weight in the temperature region 200 to 3500C can be ascribed to the loss of water molecules and decomposition of organics and nitrates. A low weight loss observed between 350 to 7000C indicates the complete decomposition of citrate-nitrate mixture above 3500C and formation of ferrite particles. It is reported in citrate-nitrate auto ignition [21] that the complete removal of organics occurs above a temperature of 4500C followed by the collapse of pores, formation and densification of nano particles. Further analysis and detection of particle size is possible only above this temperature. Hence, in spite of the completion of decomposition reaction at 3500C, final calcinations temperature is selected as 7000C for the ferrite under investigation.