Structural, Optical and Magnetic Properties of $\alpha$-${\text {Fe}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$ and ${\text {Dy}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$ Composites Produced by a Facile Method

Abstract

We prepared ${\text {SiO}}_{2}$, ${\text {Fe}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$, and ${\text {Dy}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$ composites by an enhanced method and reported the result of their structural, optical and magnetic properties. In the x-ray diffraction results of the ${\text {Fe}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$, ${\text {Fe}}_{2}{\text {O}}_{3}$ and the ${\text {SiO}}_{2}$ it is evident that these composites are crystallized in rhombohedral and trigonal structures, respectively. In the${\text {Dy}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$ composite, ${\text {SiO}}_{2}$ transforms into a trigonal structure with the addition of Dy. The absorption bands belong to ${\text {Fe}}_{2}{\text {O}}_{3}$, and ${\text {Dy}}_{2}{\text {O}}_{3}$ were obtained using the Fourier transform infrared spectra. In ultraviolet–visible spectra, the photocatalytic properties of ${\text {Fe}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$ and ${\text {Dy}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$ were determined as a function of time at room temperature. Maximum transmittance change at 800 nm was 75% and 40% for composites ${\text {Fe}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$, and ${\text {Dy}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$, respectively. The photocatalytic property of ${\text {Dy}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$ composite increases gradually from short to long in the wavelength region where it exhibits a maximum value in the visible region. In magnetic measurements, a weak ferromagnetic behavior was observed in the ${\text {Fe}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$, while ${\text {Dy}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$ exhibited paramagnetic behavior as expected. The saturation and coercivity values for ${\text {Fe}}_{2}{\text {O}}_{3}$-${\text {SiO}}_{2}$ were found to be 0.15 $\hbox {Am}^2\hbox {kg}^{-1}$ and 40 mT, respectively.