Fe-Doped Sno$_{2}$ Powders Obtained By Sol-Gel Method, Mechanochemical Alloying, and Thermal Treatment

The present work is aimed to investigate experimental conditions to obtain pure Sn$_{1-x}$F$e_{x}$O$_{2-\delta }$ ($x$=0, 0.05, and 0.1) powders by three methods: (1) sol-gel method, (2) mechanochemical alloying and (3) thermal treatment. In (1), different precursors were employed: mixtures of Sn$^{4+}$ and Fe$^{3+}$ or Sn$^{2+}$ and Fe$^{2+}$. In (2), SnO$_{2}$ and $\alpha $-Fe or $\alpha $-Fe$_{2}$O$_{3}$ were used as reactants. In (3), the Fe-doped SnO$_{2}$ were obtained by mechanochemical milling and thermal treatment.$_{ }$All samples were characterized by X-Ray diffraction (XRD) using Rietveld refinement, Fourier-transformed infrared (FTIR) spectroscopy and room temperature $^{57}$Fe M\"{o}ssbauer spectrometry (MS). The XRD patterns of samples prepared by (1) showed only peaks of SnO$_{2}$. The MS showed ferromagnetic and paramagnetic signals. The samples obtained by (2) showed XRD peaks due to SnO$_{2}$ (rutile). The MS revealed the presence of Fe$^{2+}$ and Fe$^{3+}$ states as well as $\alpha $-Fe or $\alpha $-Fe$_{2}$O$_{3}$ due to the reactants. In the case of (3) was observed total incorporation of Fe$^{3+}$ in the SnO$_{2}$ structure without presence of impurities.