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This paper reports the synthesis and characterization of the ZrO2:Co nanosystem, by incorporation of Co nanoparticles (CoNP) into tetragonal and monoclinic zirconia. ZrO2 was synthesized by a sol-gel process, while cobalt nanoparticles were obtained through a colloidal method by chemical reduction of a metal precursor. CoNP were incorporated by two different approaches: during the synthesis of the ZrO2 and by classical impregnation of CoNP on zirconium oxide. The size of Cobalt nanoparticles was controlled through the concentration of reducing agent (NaBH4) and passivanting agent (1-dodecanethiol). According to SEM and TEM analysis, the diameter of the zirconium oxide particles depends on the CoNP concentration added; the particle size for pure zirconia treated at 500°C is 200 nm and 180 nm for ZrO2:Co. X-Ray diffraction showed presence of the tetragonal and monoclinic zirconia, but the abundance of each one depends on the Co nanoparticles and thermally treatment.

Zirconia nanopowders doped with different concentrations of Eu were prepared by the solgel method followed by a thermal treatment at 500°C. Morphological and crystallographic characteristics were studied by scanning electron microscopy, X-Ray diffraction and UV spectroscopoy. Results showed a modification of the size of nanopowder particles when the concentration of Eu is increased from 0.0 to 4.0 wt%. Also, at lower concentration of Eu the tetragonal ZrO2 is the most abundant phase while high concentrations of Eu lead to the formation of the monoclinic phase. The UV spectroscopy of ZrO2 samples shows two main absorption peaks at 228 and 214 nm. The novel characteristics of the ZrO2 nanopowders doped with Eu allow us to propose them for use as solar UV radiation detectors.