Bonding characteristics, electrical and microwave/terahertz dielectric properties of novel tetragonal scheelite structure NaSrLnMo ₃ O ₁₂ (Ln = Ce, Pr, Eu, Y, Yb) ceramics for antenna application

The design of microstructures is essential for tailoring the microwave dielectric properties of ceramics, yet the structure-property relationship in tetragonal scheelite-structured ceramics remains insufficiently understood. In this study, first-principles calculations combined with experiments were used to systematically investigate the interrelations among sintering behavior, crystal structure, electrical characteristics, bond characteristics, and dielectric performance of NaSrLnMo₃O₁₂ (Ln = Ce, Pr, Eu, Y, Yb) ceramics. All compositions crystallized into a tetragonal scheelite structure (space group <em>I</em>4₁/<em>a</em>) and exhibited favorable dielectric properties with optimal sintering temperatures of 775 ~ 925 °C, <em>ε_r</em> = 9.8 ~ 10.34, <em>Q×f</em> = 30,487 ~ 69,445 GHz, and<em> τ_f </em>= −20.55 ~ −44.24 ppm/°C. Enhancement of <em>ε_r</em> originated mainly from the increased ionicity of Na/Sr/Ln-O bonds, while the improvement of <em>Q×f</em> was attributed to higher lattice energy of Mo-O bonds, elevated bond valence, and reduced ionic/electronegativity disorder. The negative shift of <em>τ_f</em> was primarily linked to the increased <em>α_L</em> of Na/Sr/Ln-O bonds. Furthermore, electrical characteristics and relaxation mechanisms were examined, and dielectric response in the terahertz range was confirmed. Finally, NaSrCeMo₃O₁₂ was employed to design and fabricate two antenna devices, verifying its potential for high-frequency communication. This work provides a systematic understanding of the role of Ln elements in optimizing the dielectric properties of tetragonal scheelite ceramics and clarifies the microscopic mechanisms underlying their performance.