Journal of the Ceramic Society of Japan
Online ISSN : 1348-6535
Print ISSN : 1882-0743
ISSN-L : 1348-6535
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Ferroelectric state in lead-free mixed-oxide system (1 − x)Na0.5Bi0.5TiO3xBaTiO3 having high Ba contents
Hirofumi TSUKASAKI
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2019 Volume 127 Issue 5 Pages 304-309

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Abstract

The ferroelectric state in a simple-perovskite mixed-oxide system (1 − x)Na0.5Bi0.5TiO3xBaTiO3 (NBT–xBT) for 0.30 ≤ x ≤ 1.0 was investigated primarily via in situ transmission electron microscopy observation. Dielectric permittivity measurements reveal that the NBT–xBT samples for 0.30 ≤ x < 0.80 exhibited hysteresis with a temperature width of approximately 20–50°C. This result suggests that a successive phase transition was present and that the ferroelectric state at room temperature was not a simple tetragonal symmetry. In situ transmission electron microscopes observation reveals that the ferroelectric state in the BT-rich end had an MC-type monoclinic symmetry with 〈201〉C polarization vectors in {100}C planes. The ferroelectric MC state was characterized by a 79° (pseudo 90°) domain with a (110)C twin structure and 180° domain. Thus, the continuous change at room temperature from the ferroelectric tetragonal state in BT for x = 1.0 to the monoclinic MC state for x = 0.30 can be explained by the introduction of a 〈100〉C component perpendicular to the original [001]C polarization vector in the tetragonal system.

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