Electric Field-Dependent Dielectric Properties and High Tunability of Porous Ba0.5Sr0.5TiO3 Ceramics

Porous Ba_0.5Sr_0.5TiO₃ (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 ?_r(0)～1690 to ?_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).