Low temperature sintering of LiF-doped CoTiNb2O8 microwave dielectric ceramics

Rutile-structured CoTiNb 2 O 8 ceramics were synthesized via traditional solid-state route. The effects of LiF addition on their sintering behavior, phase composition, microstructure and microwave dielectric properties were investigated systematically in this study. The sintering temperature was successfully lowered to 950 °C by a small amount (1 wt%) of sintering aid. XRD and EDS results indicated that chemical reaction between LiF and host ceramic took place during sintering process. And CoTiNb 2 O 8 with Li 0.8 Co 0.2 Nb 0.96 O 3 second phase coexisted in the entire composition range. The addition of LiF to the CoTiNb 2 O 8 ceramics induced a limited degradation in microwave dielectric properties. The ε r and Q  ×  f values of the low-fired CoTiNb 2 O 8 ceramics ranged from 39.4 to 53.9 and 17,580 GHz to 20,147 GHz, respectively. While the τ f decreased in negative values with increasing LiF content. When sintered at 950 °C, the CoTiNb 2 O 8 ceramic doped with 1 wt% LiF had excellent microwave dielectric properties: ε r  = 53.9, Q  ×  f  = 20,147 GHz, and τ f  = 77.2 ppm/°C, making them promising for LTCC applications.