CARLOS HENRIQUE DE MESQUITA
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Artigo IPEN-doc 23044 Purification and crystal growth of the bismuth (III) iodide-influence of trace impurities on the crystal quality2017 - FERRAZ, CAUE de M.; ARMELIN, MARIA J.A.; OLIVEIRA, RENE R.; OTUBO, LARISSA; MARTINS, JOAO F.T.; SANTOS, ROBINSON A. dos; COSTA, FABIO E.; CARVALHO, DIEGO V.S.; OMI, NELSON M.; MESQUITA, C.H.; HAMADA, MARGARIDA M.This work describes the experimental procedure of purification and preparation of BiI3 crystals by Repeated Vertical Bridgman technique, aiming a future application of this semiconductor crystal as a room temperature radiation detector. The BiI3 powder used as raw material was purified three times and, at each purification, the crystal was evaluated by systematic measurements of the reduction of the impurities, crystalline structure, stoichiometry and surface morphology. The reduction of the trace metal impurities in the BiI3, at each purification, was analyzed by Instrumental Neutron Activation Analysis (INAA), in order to evaluate the efficiency of the purification technique established in this work. It was demonstrated that the Repeated Bridgman technique is effective to reduce the concentration of many impurities in BiI3, such as Ag, As, Br, Cr, K, Mo, Na and Sb. The crystalline structure of the BiI3 crystal purified twice and three times was similar to BiI3 pattern. However, for BiI3 powder and purified once, an intensity contribution of the BiOI was observed in the diffractograms. Improvement in the stoichiometric ratio was observed at each purification step, as well as the crystal surface morphology.Artigo IPEN-doc 23998 Influence of impurities on the radiation response of the TlBr semiconductor crystal2017 - SANTOS, ROBINSON A. dos; MESQUITA, CARLOS H. de; SILVA, JULIO B.R. da; FERRAZ, CAUE de M.; COSTA, FABIO E. da; MARTINS, JOAO F.T.; GENNARI, ROSELI F.; HAMADA, MARGARIDA M.Two commercially available TlBr salts were used as the rawmaterial for crystal growths to be used as radiation detectors. Previously, TlBr salts were purified once, twice, and three times by the repeated Bridgmanmethod. Thepurification efficiency was evaluated by inductively coupled plasma mass spectroscopy (ICP-MS), after each purification process. A compartmental model was proposed to fit the impurity concentration as a function of the repetition number of the Bridgman growths, as well as determine the segregation coefficients of impurities in the crystals. The crystalline structure, the stoichiometry, and the surface morphology of the crystals were evaluated, systematically, for the crystals grown with different purification numbers. To evaluate the crystal as a radiation semiconductor detector, measurements of its resistivity and gamma-ray spectroscopy were carried out, using 241Am and 133Ba sources. A significant improvement of the radiation response was observed in function of the crystal purity.Artigo IPEN-doc 19405 Influence of impurities on the surface morphology of the TlBr crystal semiconductor2013 - SANTOS, ROBINSON A. dos; SILVA, JULIO B.R. da; MARTINS, JOAO F.T.; FERRAZ, CAUE de M.; COSTA, FABIO E. da; GENNARI, ROSELI F.; MESQUITA, CARLOS H. de; HAMADA, MARGARIDA M.Artigo IPEN-doc 18326 Purification of HgISUB(2) crystals from physical vapor transport for application as radiation detectors2012 - MARTINS, JOAO F.T.; SANTOS, ROBINSON A. dos; COSTA, FABIO E. da; MESQUITA, CARLOS H. de; HAMADA, MARGARIDA M.