Estratégias de síntese para obtenção de niobato e perovskitas a base de chumbo.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

This work reports the study on the synthesis of the solid solution 65Pb(Mg1 3 Nb2 3 )O335PbT iO3 (65PMN35PT) using combination of dierent synthesis methods, such as columbite, partial oxalate and oxidant peroxo methods. Nanosized and highly reactive magnesium niobate (MgNb2O6 or MN) powders were successfully synthesized by a new wet-chemical method by means of the dissolution of Nb2O5.5H2O and in a solution of oxalic acid (OA) followed by the addition of stoichiometric amounts of magnesium carbonate. In the next step, lead titanate (PbT iO3 or PT) precursor amorphous synthesized from the oxidant peroxo method was dispersed together with crystalline and monophasic MN in a solution of oxalic acid. A solution of Pb(NO3)2 was prepared and slowly dropped into the PT-MN-OA dispersion, resulting in a white precipitate of lead oxalate on the particles of the amorphous PT and crystalline MN. The precipitated obtained was calcined in dierent temperatures using conventional electrical furnace and microwave furnace. The thermal behavior of the 65PMN35PT it was observed by the TG and DSC analysis. The evaluation of the phases presents was followed by XRD and FT-Raman. The results of XRD revealed the existence of the phases tetragonal and monoclinic using microwave furnace in a range temperature between 700 and 800 C. Moreover, structure perovskite 65PMN35PT it was formed without the presence of secondary phases or same of the phase of the type pyroclore at 700 C for 10 minutes when calcined in microwave furnace. In this case, a model for the formation of the structure perovskite 65PMN35PT was considered based in the decomposition of lead oxalate in PbO, after that it occurs the crystallization of the PT amorphous and reaction of PbO with MN forming PMN. In the next step, the reaction in the solid state of PMN and PT crystalline for the formation of the solid solution 65PMN35PT.

ASSUNTO(S)

microondas físico-química fisico-quimica raman, espectroscopia de niobato de magnésio perovskita

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