Perovskite–Aurivillius dielectric composites for high-temperature capacitors

Abstract

High-dielectric-constant ε_r materials with stable capacitances are required for high-temperature capacitive applications. This study introduces unconventional combinations of the perovskite BaTiO₃ with Aurivillius L_n–3Bi₄Ti_nO_3n+3 (where L is Ca, Sr, or Ba, and n = 4, 5, or 6) phases as high-temperature, high-ε_r materials. The dielectric properties of the resulting composite materials strongly depended on the type and content of the Aurivillius phase. Compared with Ca_n–3Bi₄Ti_nO_3n+3 or Sr_n–3Bi₄Ti_nO_3n+3, Ba_n–3Bi₄Ti_nO_3n+3 more effectively stabilized the capacitance of the composites upon incorporation, particularly in the case of a lower n. For example, the capacitance of the BaTiO₃–BaBi₄Ti₄O₁₅ with a molar ratio of 8:2 remained stable up to 444 °C within a capacitance change of only 20 %. The structural origin of the change in dielectric permittivity depending on the L cations and n value was explored in terms of the ionic radius and octahedral distortion.