Abstract:
In Bangladesh, Cox's Bazar beach sand contains potentially valuable minerals as
discovered during a geological survey for radioactive minerals in 1961. Beach sand contains
magnetic materials in the form of magnetite. Beach sand was collected from Kolatoli sea beach;
Cox's Bazar, was washed by water to separate other unnecessary materials such as small rock,
clay, etc. Afterward, the sand was dried and fmally separated by strong magnet, Obtained
magnetite powders were gronnd by ball milling for several hours in water media. The coarse
particle fractions were eliminated by sedimentation. The raw powders are then sintered at 750°C
and 900°C for I h. X-ray diffraction studies show that the raw powders sintered at 750°C is the
best samples. From this dried fine powder of magnetite toroid and disk-shaped samples were
prepared by uniaxial pressing and sintered at various temperatures for various dwelt times.
Structural, DC and AC magnetization, and electrical transport properties of these sintered
magnetites were investigated thoroughly. X-ray diffraction studies show that the magnetite forms
spinel structure with some impurities. It was observed that the magnetite separated from beach
sand shows Verwey transition at 125 K. The sinterectmagnetite has highest magnetization about
3.5 j.lB which is about 88% magnetization value of the pure magnetite. Real part of the initial
permeability,.u:, also varies with sintering temperature and sintering time. For a fixed sintering
temperature, it is observed that .u: values increases as the sintering time increase, perhaps due to
improved microstructure.
Utilizing magnetite from the beach sand and commercially available Zno, the
Fe].,Zrtx04 (x = 0.30 and 0.5) ferrites were prepared by a conventional solid state reaction
technique. The samples were sintered at 750°C in air for I h. Structural investigation of these
ferrites was studied by x-ray diffraction. It was observed that the lattice parameter increases as
the Zn content increases, which obey the Vegards law. The DC and AC magnetic properties are
aillo investigated using SQUID magnetometer and Impedance Analyzer, respectively. It was
observed that the magnetization values fall drastically due to the substitution of In. This result
can be explained with the help of cation distribution in the A-site and B-site in the spinel
structure. However, the real part of the permeability increases and loss factor decreases due to Zn
substitution in magnetite.
