LUCIANO FABRICIO DIAS PEREIRA
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Artigo IPEN-doc 29041 Local crystalline structure of doped semiconductor oxides characterized by perturbed angular correlations2022 - BURIMOVA, ANASTASIA; CARBONARI, ARTUR W.; LIMA, NICOLE P. de; MIRANDA FILHO, ARNALDO A.; SOUZA, ALEXANDRE P. dos S.; SALES, TATIANE da S.N.; FERREIRA, WANDERSON L.; PEREIRA, LUCIANO F.D.; CORREA, BRUNO S.; SAXENA, RAJENDRA N.Doping semiconductor oxides with trace amounts of non-native elements can improve their properties such as bandgap and conductivity. The lack of local techniques makes the precise characterization of these materials difficult. Among the few techniques capable of providing local characterization, those based on hyperfine interactions at probe nuclei have the advantage of being well established, probing the material homogeneously and completely, thus investigating different regions of material. Some of these techniques are also quite sensitive even at extremely low dopant concentrations. The perturbed angular correlation technique, combined with first-principles calculations, has recently been shown to be a powerful method for characterizing doped semiconductor oxides. In this paper, we present a brief review of the unique information extracted from the semiconductor investigation with such a complex approach, including semiconductor oxides doped with cadmium and other elements. A strong relationship between the local environment, including electronic structure, and the nature of the dopant and the native element of the doped oxides is also shown.Artigo IPEN-doc 27751 Synthesis and characterization of Fe3O4-HfO2 nanoparticles by hyperfine interactions measurements2021 - SALES, T.S.N.; BURIMOVA, A.; RODRIGUES, P.S.; MATOS, I.T.; CABRERA-PASCA, G.A.; SAXENA, R.N.; PEREIRA, L.F.D.; OTUBO, L.; CARBONARI, A.W.Nanoparticles (NPs) that combine biocompatibility and enhanced physical characteristics for biomedical applications are currently an area of intense scientific research. Hafnium oxide NPs are an innovative approach in the anticancer treatment by radiotherapy due to their low toxicity and enhancement of local dose in the tumor reducing the total radiation dose for the patient. The combination of this property with the excellent magnetic hyperthermia performance of Fe3O4 NPs can produce a promising nanomaterial for cancer therapy. In this work, we attempted to synthesize nanoscale samples of HfO2 doped with nominal 10 at.% Fe, and Fe3O4 doped with Hf at 10 at.% level using simple chemical routes. The crystal structure of the samples was characterized by X-ray diffraction. The material was irradiated with neutrons in a research reactor, the nuclear reaction 180Hf(n, γ)181Hf yielding the probe nucleus 181Hf(181Ta) used in the perturbed angular correlations experiments to measure hyperfine interactions. Despite their immediate response to the external magnetic field, at local level both samples showed only electric quadrupole interaction typical of the monoclinic hafnia indicating that Fe replaces Hf in HfO2 NPs, but, rather than substituting Fe, Hf enters magnetite in the form of HfO2 clusters. Transmission Electron Microscopy was exploited to study the morphology of these complex systems, as well as to localize hafnia clusters and understand the nature of their coupling to Fe3O4 specks.