Preparação e caracterização de materiais ferroelétricos de composição Bi4Ti3O12 contendo Lantânio e Érbio / Synthesis and characterization of Bi4Ti3O12 ferroelectric materials containing Lanthanum and Erbium

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

This work describes a systematic study of the influence of the lanthanum atom addition in the Bi4Ti3O12 (BIT) phase and the erbium atom addition in the Bi3,25La0,75Ti3O12 (BLT075) phase in terms of their synthesis process and its structural, microstructural and electrical properties. Ceramics of nominal composition Bi4-xLaxTi3O12 (BLTx) with 0 x 2 mol% and Bi3,25La0, 75Ti3O12 (BLT075) with Er3+ replacing the La3+ atoms (BLExT) and replacing Ti4+ atoms (BLTEx) with 0 x 0, 06 mol%, were prepared by the solid state reaction method. X-ray diffraction (XRD) data of BLTx samples shows the formation of a solid solution for all samples, except for sample containing 2 mol% of La3+. It was found that the addition of La3+ leads to an increase in the sintering temperature, a decrease in the average size of grains and a modification on the grain from plates to a more spherical morphology. The dielectric properties of BLTx samples with x 1 mol% show a behavior characteristic of a normal ferroelectric whereas when x>1 mol%, there is a small displacement of the temperature of maximum dielectric permittivity (Tm) with the frequency, indicating the existence of a typical behavior of a relaxor ferroelectric material. The Raman spectroscopy results suggest that La3+ ions tend to preferentially occupy the Bi3+ site in the peroviskite layer when x <1.0 mol%, whereas when x>1.0 mol%, the process of incorporation occurred also in the Bi3+ site of the Bi2O2 layer. According to the analysis of XANES and XPS spectra, the local structure of atoms and electronic structure of Ti, Bi and La atoms of BLTx samples are not affected significantly by the addition of lanthanum. For samples of BLExT and BLTEx systems, the XRD data shows only the presence of a secondary phase in the x = 0.04 and 0.06 mol% compositions of the BLTEx system. The sintering at 1115 °C allowed to obtain samples presenting a relative high density than the sample BLT075 undoped sample. The addition of Er3+ induces significative changes in grain morphology by decreasing the average size of grains in the BLExT system and by increasing the BLTEx system. Through electrical measurements, it was observed a decrease in the Tm value in both cases. In the BLExT system, when x>0.02 mol%, the behavior of Tm is dominated by the solubility limit. According to the XAS data, the local and electronic structure of Ti and Er atoms are not affected significantly by the addition of erbium.

ASSUNTO(S)

microstructural and structural characterization calcinação e sinterização electrical properties lanthanum and erbium calcination and sintering propriedades elétricas bi4ti3o12 ferroelectric ceramics cerâmicas ferroelétricas de bi4ti3o12 lantânio e érbio caracterização estrutural e microestrutural

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