The relationship between crystal structure and modified microwave dielectric properties of Ca <sub>3</sub> SnSi <sub>2‐</sub> <i> <sub>x</sub> </i> Ge <i> <sub>x</sub> </i> O <sub>9</sub> ceramics
Kang Du, Changzhi Yin, Yan‐Bo Guo, Xiao‐Chuan Wang, Wenzhong Lü, Shiwo Ta, Chun‐Yuan Hu, Wen Lei
Abstract
Abstract Ca 3 SnSi 2‐ x Ge x O 9 (0 ≤ x ≤ 0.8) and (1– y ) Ca 3 SnSi 1.6 Ge 0.4 O 9 – y CaSnSiO 5 – 2 wt% LiF ( y = 0.4 and 0.5) microwave dielectric ceramics were prepared by traditional solid‐state reaction through sintering at 1250°C–1425°C for 5 h and at 875°C for 2 h, respectively. Ge 4+ replaced Si 4+ , and Ca 3 SnSi 2‐ x Ge x O 9 (0 ≤ x ≤ 0.4) solid solutions were obtained. At 0.1 ≤ x ≤ 0.4, the Ge 4+ substitution for Si 4+ decreased the sintering temperature of Ca 3 SnSi 2‐ x Ge x O 9 from 1425 to 1300°C, the SnO 6 octahedral distortions, and the average CaO 7 decahedral distortions, which affected the τ f value. The large average decahedral distortions corresponded with nearer‐zero τ f values at Ca 3 SnSi 2‐ x Ge x O 9 (0.1 ≤ x ≤ 0.4) ceramics. The τ f value and sintering temperature of Ca 3 SnSi 2‐ x Ge x O 9 ( x = 0.4) ceramic were adjusted to near‐zero by CaSnSiO 5 and decreased to 875°C upon the addition of 2 wt% LiF. The (1 – y ) Ca 3 SnSi 1.6 Ge 0.4 O 9 – y CaSnSiO 5 – 2 wt% LiF ( y = 0.5) ceramic sintered at 875°C for 2 h exhibited good microwave dielectric properties: ε r = 10.3, Q × f = 14 300 GHz (at 12.2 GHz), and τ f = ‒5.8 ppm/°C.