**3.1 Thermal treatment method**

In the present study, spinel ferrites nanocrystals with different structures were prepared from an aqueous solution containing metal nitrates, poly (vinyl pyrrolidon), and deionized water using a relatively low temperature thermal treatment method, followed by grinding and calcinations\*. No other chemicals were added to the solution. This method is environmentally friendly in that it neither uses nor produces toxic substances, and it offers the advantages of simplicity, low cost, and low reaction temperatures. The textural and morphological characteristics of the spinel ferrites nanocrystals we prepared were studied with various techniques to determine the influence of calcination temperature on the crystallization, morphology, and particle size distribution of the nanocrystals and to explore other parameters of interest.

<sup>\*</sup> This method was invented by Mahmoud Goodarz Naseri in university Putra Malaysia in 2011

Crystalization in Spinel Ferrite Nanoparticles 363

N

<sup>O</sup> <sup>O</sup>

<sup>H</sup> <sup>O</sup> H

H O H

<sup>H</sup> <sup>O</sup> H

H O H

O

N

Fig. 15. The proposed mechanism of interactions between PVP and metal ions in the

Drying 2Fe3+,

N

H O H

H <sup>O</sup> <sup>H</sup>

Me+2, 8NO3

C a l c i

na t i o n

N

O

H O H

H <sup>O</sup> <sup>H</sup>

<sup>M</sup> MeFe2O4 MeFe2O4 MeFe2O4 eFe2O4

Nuclea ti o n PVP removing


2Fe3+,

N

O

N

H O H

O

Me+2, 8NO3


n

formation of the ferrites nanoparticles.

H2O, 2Fe3+,

Fe3+ Me2+ NO3 -

<sup>N</sup> <sup>O</sup> <sup>N</sup> <sup>O</sup>

H2O, 2Fe3+,

Me+2, 8NO3


Me+2, 8NO3

