查找使用阿拉丁产品的科研文献

Enhanced microwave dielectric properties of spinel-garnet ceramics based on MgO-Al2O3-Y2O3 ternary systems: A study on solid solutions and composite synergistic strategies

Jian Li,Jia Liu,Yeqing He,Xiaohan Zhang,Yanxiang Jiang,Yang Wang,Wei Sun,Yuanyuan Zhou,Walther Glaubitt,Futian Liu,Haitao Wu,Fei Wang,Ling Li

High-performance dielectric ceramics are vital for next-generation microwave devices, requiring advanced doping and composite strategies to enhance material properties. The (1- x )MgAl 2 O 4 - x Y 3 Al 5 O 12 composite ceramics were found in the MgO-Al 2 O 3 -Y 2 O 3 pseudoternary phase diagram and synthesized via solid-phase reaction. The two phases coexist to improve grain size distribution and achieve a low eutectic temperature, allowing x  = 0.1–0.7 samples to gain a dense microstructure ( ρ  > 96 %) when sintered at 1650–1670 °C. The semi-coherent interface, coupled with the Mg 2+ /Y 3+ cation transition zone, promotes the formation of a partial solid solution, thereby alleviating interfacial stress at the grain boundaries between MgAl 2 O 4 and Y 3 Al 5 O 12 . Notably, the 0.3MgAl 2 O 4 -0.7Y 3 Al 5 O 12 ceramic exhibits satisfying microwave dielectric properties: ε r  = 10.1 ± 0.24, Q  ×  f  = 195,000 ± 12,000 GHz, and τ f  = −11.9 ppm/°C. In addition to phase composition and microstructure, the enhanced performance can be attributed to the optimized crystal structure. The partial substitution of Y 3+ by Mg 2+ with a smaller radius induced the “rattling” effect and abnormal large permittivity in the [YO 8 ] site. The 27 Al NMR spectra revealed an increase in the Mg-Al inversion degree in the Mg-deficient spinel structure, resulting in the elevated total covalency of the Al-O bond. The structural changes corresponded to a decrease in intrinsic dielectric loss in Mg-Al spinel and an increase in τ f in the Y-Al garnet phase. These findings indicate the (1- x )MgAl 2 O 4 - x Y 3 Al 5 O 12 ceramics have promising applications in the field of HTCC millimeter wave communications.