PROPERTIES OF Sr_1–xLA_2x/3Bi₄Ti₄O₁₅ FERROELECTRIC CERAMICS

ABSTRACT

Dielectric and ferroelectric properties of La-doped Sr_1–x La_2x/3Bi₄Ti₄O₁₅ (SLBT-x, x = 0.00–0.75) ceramics were investigated. A single phase is achieved up to x = 0.30. The temperature dependence of dielectric permittivity (ϵ) for SLBT-x shows the Curie temperature (T _c ) decreases with increasing La content, implying the relaxation of lattice distortion, meanwhile the peak of the ϵ-T curve decreases and broadens, indicating the dispersion of phase transition. The A-site vacancies induced by the substitution of La^{3 +} for Sr^{2 +} weakened the coupling between the neighboring TiO₆ octahedra and gave rise to the relief of lattice distortion. The broadening of dielectric peak may be attributed to the difference of ionic radii between La^{3 +} and Sr^{2 +} as well as the exchange of La^{3 +} at A-site and Bi^{3 +} at bismuth oxide layer. The hysteresis loops of SLBT-x shows the La-substitution increased the 2P _r up to 23.1 μ C/cm² and lowered E _c down to 79.6 kV/cm. It may be related to the dipole defects induced by higher-valence-doping at A-site.

Keywords:

• Ceramics
• dielectric properties
• ferroelectricity

ACKNOWLEDGMENTS

This work was supported by the financial support from the National Natural Science Foundation of China (Grant No. 10274066) and the Natural Science Foundation of Education Bureau of Jiangsu Province, China (Grant No. GK0410181). Partial support was also provided by the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2005052).