One-step synthesis of Li₂Mg₂Mo₃O₁₂-(Li_1/2Bi_1/2)MoO₄ composite ceramics with a stable temperature coefficient for ULTCC applications

Dielectric materials with near-zero τ_f values are needed to enhance the thermal stability of devices and ensure their stability during temperatures changes. In this study, the introduction of the (Li_1/2Bi_1/2)MoO₄ phase was employed to regulate the τ_f of the Li₂Mg₂Mo₃O₁₂ system. A temperature-stable Li₂Mg₂Mo₃O₁₂-(Li_1/2Bi_1/2)MoO₄ composite ceramics were successfully synthesized using a one-step direct synthesis approach for the first time. The synthesis involved controlling the Li₂CO₃ : MgO : Bi₂O₃ : MoO₃ ratios at 1 : (2 − 1.5x) : x/2 : 3 (x = 0.02 – 0.30). The impacts of different x values on phase composition, sintering properties and microwave dielectric properties were investigated. X-ray diffraction and Roman spectroscopy revealed the coexistence of the two phases without other miscellaneous phases. When x = 0.15, the excellent microwave dielectric properties were obtained with samples sintered at 600 °C for 2 h: ε_r = 11.4, Q×f = 41,592 GHz (f = 11.2 GHz), τ_f = − 8 ppm/°C.