High hysteresis-free dielectric tunability in silver niobate-based ceramics

Moderate dielectric constant, low dielectric loss, and high dielectric tunability around or above Curie temperature are essential characteristics of dielectric tunable devices. Silver niobate (AgNbO₃), known for its antiferroelectric (AFE) and weak ferroelectric (FE) nature, offers a natural “composite” system combining AFE and FE attributes, making it an attractive candidate for tunable device materials. Microstructural modification through chemical methods can enhance its dielectric tunability. To this end, we propose and prepare a doped AgNbO₃ ceramic system, denoted as (1-x) AgNbO₃-xLiTaO₃ (ANLT100x, x ≤ 3.8 mol%). Structural analysis reveals that all samples maintain an average AFE-like polar structure. The introduction of dopants disrupts the ordered AFE-like structure, altering the proportion of AFE and FE states. This disruption leads to a notably improved relaxor dielectric response and an FE transition around room temperature. Consequently, we achieve a ceramic material (x = 3.8 %) with a moderate dielectric constant (ε_r = 520) and low dielectric loss (tanδ = 0.008), accompanied by a hysteresis-free dielectric tunability (n_r = 37.2 %) under an applied bias electric field of 40 kV cm⁻¹, which is four times larger than that in AgNbO₃ (n_r = 8 %) ceramic. These findings open new possibilities for developing dielectric tunable materials in device design.