**2. Preparation of hematite (α-Fe2O3) nanoparticles**

Prior to the preparation of α-Fe2O3 nanoparticles, at first, Fe3O4 nanoparticles were synthesized from natural iron sand as the raw material by coprecipitation technique using HCl as dissolving agent and NH4OH as precipitating agent. The detail of experimental procedure to synthesize Fe3O4 nanoparticles was also described in elsewhere [3]. First of all, the extracted iron sand was collected and dissolved in 12 M HCl at ~70°C under continuous and constant stirring of 600 rpm. The obtained solution from the reaction process was filtered and added slowly with 6.49 M NH4OH under the same temperature and stirring speed for 30 minutes. Then, the black precipitates were formed. The precipitate (Fe3O4 phase) was initially washed with distilled water until pH 7 and then dried at 70°C for 5 h. In order to get α-Fe2O3 phase, the dried nanopowder (Fe3O4 phase) was calcined at 800°C for 2 h, as shown in **Figure 1**. Finally, the Fe2O3 powders from this calcination were continued by performing coprecipitation process again with the same experimental procedure as before until the precipitation process. A reddish

#### **Figure 1.**

*Hematite (α-Fe2O3) synthesized from natural iron sand (Fe3O4) by coprecipitation method followed by calcination process at 800°C for 2 h.*

**37**

**5. Characterizations**

*Ferrite-Based Nanoparticles Synthesized from Natural Iron Sand as the Fe3+ Ion Source*

precipitate (Fe2O3.H2O) was formed. The resulted precipitate was then washed and collected for further synthesis of CaFe4O7 and BiFeO3 (without and with doping of

Calcium biferrite (CaFe4O7) nanoparticles were synthesized by the so-called chemically dissolved method using precipitated CaCO3 and Fe2O3 as Ca2+ and Fe3+ ion sources, respectively. Fe2O3 powders were obtained as described previously from natural iron sand, whereas the precipitated CaCO3 particles were synthesized from natural limestone through carbonation process. First, the natural limestone was extracted from the existing impurities, such as silica, and then it was calcined at 900°C for 6 h to produce CaO. The CaO powder was dissolved into distilled water to produce Ca(OH)2 solution. The carbonation process using CO2 gas flow was performed until it formed a precipitation at pH around 7. The precipitated CaCO3 was filtered and dried for further synthesis. The detail procedure was also explained

In the synthesis of the calcium ferrite nanoparticles using the chemically dissolved method, the obtained Fe2O3 and precipitated CaCO3 were dissolved in HNO3 to get Fe(NO)3 and Ca(NO)2 solutions, respectively, with a molar ratio of 1:6. Both solutions were mixed homogeneously and heated at constant temperature (80°C) and stirring rate (600 rpm) until it formed slurry precipitates. The precipitates were washed using distilled water and dried at 80°C for 10 h. The resulted powders

**4. Preparation of bismuth ferrite (BiFeO3) nanoparticles without and** 

Nanoparticles of undoped, Pb- and Ni-doped BiFeO3 (BiFeO3, Bi0.9Pb0.1FeO3, and BiFe0.9Ni0.1O3, respectively) were prepared by sol-gel method. The starting materials were Fe2O3 synthesized previously from iron sand (94%) as the Fe3+ ion source and Bi2O3 (Aldrich, 99.9%) as the Bi3+ ion source. Pb(NO3)2 (powder, 99%) and Ni(NO3)2.6H2O (powder, 99%) were used as the Pb and Ni doping, respectively. Fe2O3, Bi2O3, Pb(NO3)2, and Ni(NO3)2.6H2O powders were dissolved separately by HNO3 (Merck, 65%) to form solutions of ferrite nitrate, bismuth nitrate, lead nitrate, and nickel nitrate, respectively, with the stoichiometric molar ratio of (Bi, Pb):(Fe, Ni) = 1:1. Acetic acid was added into each solution under constant stirring and temperature for 30 minutes. Then, it was followed by addition of ethylene glycol under the same condition. Next, the obtained solutions were mixed together under the same temperature and stirring rate for 1 h. The resulted solution was dried at 80°C for 6 days to obtain the undoped and doped BiFeO3 xerogels. The dried gels were ground and collected. Finally, the powders were calcined in air at 650 and 700°C for 1 h to form undoped BiFeO3 and doped BiFeO3 (Bi0.9Pb0.1FeO3

A thermogravimetric/differential thermal analysis (TG/DTA) was performed

to determine the thermal behaviors of the dried gel of bismuth ferrite. The phase formation and crystal structure of all samples were characterized by X-ray

*DOI: http://dx.doi.org/10.5772/intechopen.88027*

in the former paper by Arifin et al. [61].

**with Pb and Ni doping**

were collected and then sintered at 800°C for 3 h.

and BiFe0.9Ni0.1O3), respectively, for further characterizations.

**3. Preparation of calcium ferrite nanoparticles**

Pb and Ni) nanoparticles.

precipitate (Fe2O3.H2O) was formed. The resulted precipitate was then washed and collected for further synthesis of CaFe4O7 and BiFeO3 (without and with doping of Pb and Ni) nanoparticles.
