Low‐Temperature Synthesis of CoNb 2 O 6 Microwave Dielectric Ceramics

Low‐fired cobalt niobate (CoNb 2 O 6 ) microwave dielectric ceramics were prepared through a developed sol–gel process using Nb 2 O 5 · n H 2 O as starting source. A metal‐dioxo‐bridged complex precursor was described on the basis of FT ‐ IR spectrum. The crystalline phases of calcined powders were characterized by X‐ray diffraction. Nanosized CoNb 2 O 6 particles with orthorhombic α‐PbO 2 ‐type structure were obtained above 750°C. There was no subsequent phase change upon sintering, and all compounds sintered to at least 94% of theoretical density. At 1000°C/4 h, CoNb 2 O 6 ceramics exhibited ε r ~ 21.9, Q × f ~ 66 140 GH z (at 8.9 GHz) and τ f ~ −39.7 ppm/°C, having a good potential for low‐temperature cofired ceramic applications.