Mn–Si synergistically co-doping adjusting microstructures and microwave-millimeter-wave dielectric properties of Y3Al5O12 garnet ceramics: Lattice occupancy and ligand distortion perspective

Y 3-x Mn x Al 5-x Si x O 12 (x = 0.1–0.5) ceramics were fabricated through the high-temperature reaction method. The effects of Mn 2+ -Si 4+ co-doping on lattice occupancy, ligand distortion and microwave dielectric properties of Y 3 Al 5 O 12 garnet were inquired. Mn 2+ ions successively occupy the lattice sites of Y 3+ dodecahedron and Al 3+ octahedron along with the increase of distortion degree of [AlO 6 ] octahedron. In Y 3-x Mn x Al 5-x Si x O 12 , ε r predominantly correlates with ionic polarizability , average bond ionicity (△ f i ) and Mn 2+ ionic lattice occupation. The Q ×  f is primarily influenced by factors like relative density, lattice energy (U) and atomic packing fraction. Meanwhile, τ f is associated with the distortion of octahedra, bond energy (E), and the bond valence between Y/Mn and O. Ultimately, the microwave and millimeter-wave dielectric properties of the Y 2.8 Mn 0.2 Al 4.8 Si 0.2 O 12 ceramics excel with values of ε r  = 10.89, Q ×  f  = 56,135 GHz@11 GHz (Q ×  f  = 88200 GHz@25 GHz), and τ f  = -39.35 ppm/°C.