Nanostructuration effects on the dielectric and ferroelectric properties Ba0.2Na0.8Ti0.2Nb0.2O3 polycrystal

Reference	Presenter	Authors (Institution)	Abstract
03-014	Jaciele Marcia Rosso	Rosso, J.M.(Universidade Estadual de Maringá); Burato, J.A.(Maringá State University); Santos, G.M.(Maringá State University); Bonadio, T.G.(Universidade Estadual do Centro-Oeste); Silva, D.M.(Maringá State University); Sanguino, G.(Maringá State University); Freitas, V.F.(Universidade Estadual do Centro-Oeste); Cótica, L.F.(Maringa State University); Santos, I.A.(Maringa State University);	materials usually exhibit physical and chemical properties that differ from those with micrometric dimensions. Ceramic materials based on barium titanate (BaTiO3) have a wide range of applications as multilayer ceramic capacitors, mainly due to their high dielectric constant and good stability with temperature variation [1]. The aim of this work is to study the effects of nanostructuration on the structural and eletrical properites of Ba0.2Na0.8Ti0.2Nb0.8O3 ceramics. In this way, BaTiO3 was added to sodium niobate (NaNbO3) to improve its dielectric properties and induces ferroelectricity at room temperature [2]. Single-phased Ba0.2Na0.8Ti0.2Nb0.8O3 samples were processed by dry high-energy ball milling (HEBM) of BaCO3, TiO2, Nb2O5 and Na2CO3, at 300 rpm for 3 h, with a ball to powder mass ratio of 12:1, followed by heat treatments in oxygen atmosphere. These samples were nanostructured by performing a second HEBM process for 24 h. Room temperature X-ray diffraction measurements were performed, and the Rietveld analysis revealed, for all processed samples, the coexistence of two phases, one cubic (Pm-3m space group) and other tetragonal (P4mm), and that the re-milling processes resulted in samples with up to 93% of the tetragonal phase. The protocols of synthesis also allowed producing ceramics with elevated densities, reaching 96% of the theoretical one. These elevated densities, along with the coexistence of phases, are directly related to the complete control of the synthesis processes, resulting in elevated dielectric constants (~6000) and small dielectric losses (5%) at room temperature and 1 KHz
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