Transition Metal-Doped ZrO2 and HfO2 Nanocrystals

Manganese- and chromium-doped ZrO2 and HfO2 nanoparticles were synthesized by a nonaqueous sol-gel approach in benzyl alcohol. The synthesis led to high quality nanocrystals of uniform size and shape, presenting a homogeneous distribution of the magnetic ion. The crystallographic phase was studied by X-ray diffraction, electron diffraction, and high resolution transmission electron microscopy. The doping efficiency and the oxidation states of the transition metal ions in the matrixes were characterized by chemical analysis, electron paramagnetic resonance and diffuse reflectance spectroscopy. These studies were conducted to elucidate the relation between the synthesis and annealing conditions and the dopant state. Therefore, this complete study can be seen as a step forward toward a rational approach to multimetal and doped metal oxide nanocrystals. Finally, susceptibility measurements and the analysis of the magnetic properties provided additional insight oil the doping behavior of manganese and chromium in the synthesized nanocrystals.