Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1521510 | Materials Chemistry and Physics | 2015 | 13 Pages |
Abstract
Structural and electrical properties of Lanthanum substituted barium bismuth titanate BaBi4-xLaxTi4O15 (0 â¤Â x â¤Â 0.50) ceramics prepared by conventional solid-state reaction method have been investigated. Raman spectra reveals the distribution of lanthanum into the perovskite layers and (Bi2O2)2+ layers of BaBi4Ti4O15 ceramics. Room temperature dielectric constant (εâ²) increases and considerable reduction in the low frequency (10â2 to 10 Hz) dielectric losses and in dc conductivity (Ïdc) are seen with lanthanum substitution. A critical La content of x â¼0.20 in BaBi4-xLaxTi4O15 exhibits a well-defined relaxor behavior as seen from the temperature and frequency dependence of the dielectric parameters εʹ(T) and εâ³(T). The dielectric data fit well to the modified Curie-Weiss law and the Lorentz-type relation and show increasing diffuseness in the phase transition with increasing La content. The temperature dependence of the characteristic relaxation time obtained from the Cole-Cole model shows a good fit to the non-linear Vogel-Fulcher relation. Improvements in the remnant polarization and a stable piezoelectric charge coefficient are seen up to a La content of x â¼0.20. The observed increase in dielectric loss and Ïdc in addition to the diminished ferroelectric/piezoelectric properties for higher La content are explained in terms of changing oxygen vacancy concentration and structural relaxation due to the preferential incorporation of La into the (Bi2O2)2+ layers as evidenced through the Raman spectroscopy.
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Authors
Anita Khokhar, Parveen K. Goyal, O.P. Thakur, A.K. Shukla, K. Sreenivas,