Electric Field‐Dependent Dielectric Properties and High Tunability of Porous Ba _0.5 Sr _0.5 TiO ₃ Ceramics

Abstract

Porous Ba 0.5 Sr 0.5 TiO 3 (BST) ceramics were fabricated by the traditional solid‐state reaction process, and their structural, microstructural, dielectric, and tunability properties were systemically investigated. Compared with the fully dense BST samples, porous samples exhibit smaller grain sizes, a more uniform microstructure, and much lower dielectric constants, while at the same time, exhibiting little increase in tunability, which is beneficial to the development of microwave‐tunable applications. At a frequency of 10 kHz and a temperature of 18°C, as porosity increased from 0% to 28.8%, the dielectric constant of the BST ceramics (under zero bias field) decreased from ɛ r(0) ∼1690 to ɛ r(0) ∼990, while the dielectric losses were still less than 0.2%, and the tunability increased from 17.6% to 19.6% (2.6 kV/mm).