Achieving ultra-low thermal expansion and excellent microwave dielectric properties in osumilite-type BaMg 2Al 6Si 9− x Ge x O 30 ceramics

作者：Chengyun Li, Kang Du, Mengdie Zhou, Yongchao Ge, Yuan Wang, Guochao Wei, Weijia Han, Wei Zhu, Xinying Liu, Zixiong Sun, Lei Wen, Shengxiang Wang · 发表于：Journal of Advanced Ceramics · 年份：2025 · DOI：10.26599/jac.2025.9221146 · 被引用次数：12 · 研究领域：Microwave Dielectric Ceramics Synthesis、Ferroelectric and Piezoelectric Materials、Advanced ceramic materials synthesis

Excellent microwave dielectric properties and ultra-low thermal expansion are essential for dielectric ceramics in high-frequency substrate applications. However, the inherent constrains among these three key microwave dielectric properties make it challenging to simultaneously achieve ultra-low ε r , high Q×f , and near-zero τ f values in existing materials. Particularly, the coefficient of thermal expansion of microwave dielectric ceramics often exhibits values around 10 ppm/°C, offering limited tunability. In this work, based on a novel osumilite-type BaMg 2 Al 6 Si 9 O 30 ceramic with high crystal structural symmetry and excellent stability, we designed a strategy involving the substitution of Si 4+ with larger Ge 4+ ions. Replacing Si 4+ with larger Ge 4+ ions directly elongated the Si/Al(1)-O bond length while reducing the Si/Al(1)-O(1)-Si/Al(1) angle ( σ ₂). This structural modification suppressed the longitudinal vibration of 2-coordinate O(1) along the a -axis, effectively inhibiting negative thermal expansion and yielding a reduced CTE within the operational temperature range. Simultaneously, the elongation of the Si/Al(1)-O bond cooperatively increased the Si/Al(1)-O(2)-Si/Al(1) angle ( σ ₁) and enhanced the relative covalency of the Si/Al(1)-O bond, synergistically improving Q×f values. Importantly, Ge 4+ substitution preserved the ultra-low ε r and near-zero τ f values by maintaining the polarization characteristics and crystal structural sta...