Scheelite-structured Ag0.5RE0.5MoO4 microwave dielectric ceramics: Crystal structure design, chemical bond characteristics, and DRA application for 5G/6G communications

Two tetragonal scheelite Ag 0.5 RE 0.5 MoO 4 (RE = Nd, Y) ceramics with space group I 4 1 / a were synthesized via the solid-state reaction method. Ag + and RE 3+ co-occupy the dodecahedral A-site, while Mo 6+ occupies the tetrahedral B-site. Ag 0.5 Nd 0.5 MoO 4 sintered at 825 ℃ shows a higher Q × f of 92,000 GHz, with ε r = 12.14 and τ f = -62.85 ppm/℃. Ag 0.5 Y 0.5 MoO 4 sintered at 850 °C exhibits ε r = 12.96, Q × f = 56,000 GHz, and τ f = -46.22 ppm/℃. The structure-property relationship was systematically investigated using bond valence, ionic polarizability, Raman spectroscopy, and P-V-L chemical bond theory. The larger deviation Δ ε r in Ag 0.5 Y 0.5 MoO 4 originates from the stronger overall cation rattling effect and the insufficient average ionic bonding caused by its more negative weighted average deviation factor < d > . Q × f is strongly dependent on lattice vibration damping, conductive activation energy, lattice energy, and stability of rare-earth ions. Positive τ αm values mainly govern the sign and magnitude of τ f , and the intense rattling effect of Y 3+ drives τ f closer to zero. Finally, a cylindrical dielectric resonator antenna (CDRA) was designed and simulated using Ag 0.5 Nd 0.5 MoO 4 ceramic, demonstrating its potential for high-frequency communication applications.