Strong polarization in paraelectric tungsten–bronze systems via bond engineering†

Abstract

High-performance dielectrics with high permittivity (κ) as well as low loss (tan δ) are a fundamental requirement as crucial components for the miniaturization of electrical and electronics systems. Recently, tungsten–bronze paraelectrics have shown great promise as dielectrics with relatively high permittivity and low loss. We demonstrate substantial enhancements in permittivity for paraelectric ceramics through a bonding tailoring strategy by introducing Bi ions into the Ba₄Nd_28/3Ti₁₈O₅₄ tungsten bronze structure. The introduction of heavy Bi ions with 6s electrons into the lattice expands it, breaks the symmetry, and tilts the M–O octahedron, resulting in κ being enhanced by more than two times, while the tan δ remains low. As a result, the Ba₄(Bi_0.5Nd_0.5)_28/3Ti₁₈O₅₄ exhibits a high κ ∼200 with low tan δ ∼0.0004. This bonding strategy is expected to be generally applicable to tailoring dielectric and other related functionalities.