Dielectric and ferroelectric properties of (Bi0.5Na0.5)0.94Ba0.06Ti1−xAlxO3−δ lead-free ferroelectric ceramics

Microstructure and dielectric properties of the lead-free ferroelectric ceramics (Bi0.5Na0.5)0.94Ba0.06Ti1−xAlxO3−δ (abbreviated as BNBTA/x, x = 0, 0.04, 0.06, 0.08) obtained via a solid-state reaction method were studied. The ceramics with x≤0.06 exhibit pure structure without detectable secondary phase by X-ray diffraction measurement. There appears a second phase in the ceramic BNBTA/0.08. With an increase in the Al3+ amount, dielectric constant of the ceramics decreases, and the change in dielectric constant with increasing temperature between the two dielectric characteristic temperatures (TRE and Tm) is gradual. The poled ceramic BNBTA/0 shows a steep increase in permittivity at the temperature denoted as Td around 100 °C. But, the poled ceramics with x > 0 do not exhibit the Td anomaly on the permittivity spectra. The diffuse dielectric behavior around Tm was studied via the Curie–Weiss law and modified Curie–Weiss law. Compared to the ceramic BNBTA/0, the Al3+ -doped ceramics show slim ferroelectric hysteresis loops. The temperature-dependent ferroelectric properties and energy-storage behavior were studied.