Low‐Temperature Sintering Behavior and Microwave Dielectric Properties of Li 2 Co(WO 4 ) 2 Ceramics Toward Ultra‐Low‐Temperature Co‐Fired Ceramic Applications

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Ultra‐low‐temperature co‐fired ceramic (ULTCC) technology is attractive for miniaturized radio frequency front‐end modules. Li 2 Co(WO 4 ) 2 ceramics are promising candidates owing to their relatively low sintering temperature and favorable dielectric properties. In this study, high‐purity Li 2 Co(WO 4 ) 2 ceramics were synthesized via a conventional solid‐state reaction route using Li 2 CO 3 , CoO, and WO 3 as raw materials. The thermal behavior of the precursor powders was evaluated by thermogravimetry–differential scanning calorimetry and derivative thermogravimetry, while phase formation, microstructure, densification, and microwave dielectric properties were investigated for ceramics sintered at 625°C–700°C. Thermal analysis indicated that calcination at 600°C largely suppressed the major mass‐loss processes, while X‐ray diffraction confirmed the formation of phase‐pure Li 2 Co(WO 4 ) 2 ceramics after sintering. The sample sintered at 675°C achieved the highest bulk density of 6.467 g·cm − 3 , corresponding to a relative density of approximately 93.55% and an estimated total porosity of approximately 6.45%. Correspondingly, the best overall microwave dielectric properties were obtained at 675°C: ε r = 12.488, Q × f = 10,979.1 GHz, and τ f = −71.95 ppm/°C. Comparison with literature‐reported values suggests that Q × f is particularly sensitive to processing conditions and microstructural defects. These findings provide guidance for controlling densification and dielectric loss in tungstate‐based ULTCC ceramics.