Dielectric tunability performance and structural evolution of Ba_0.6Sr_0.4TiO₃-based ceramics by BaCuSi₄O₁₀/BaCuSi₂O₆ modification

Tunable dielectric materials are critical components in modern communication technologies such as phased array antennas, microwave devices, and reconfigurable phase shifters [1–2]. Ba_0.6Sr_0.4TiO₃-based (BST) ceramics exhibit exceptional dielectric tunability whereas their inherently high permittivity limits practical implementation. This study addresses this challenge by strategically incorporating BaCuSi₄O₁₀/BaCuSi₂O₆ (BCS114/BCS112) into BST to engineer composites with tailored dielectric properties, specifically, dielectric permittivity (ε_r), loss (tanδ) and tunability (T). Phase analysis reveals distinct structural pathways: BCS114 reacts with BST to form Ba₂TiSi₂O₈ and BCS112 may also decompose into Ba₂CuSi₂O₇. These phase evolutions enable precise control over dielectric performance, in which BST-BCS114 (30 wt%) composite achieves a balanced profile with ε_r of 922, tanδ of 0.0091, and tunability of 37.4%, and BST-BCS112 (50 wt%) offers ε_r of 225, tanδ of 0.0101, and tunability of 22.4%.