Low‐temperature sintering and thermal stability of Li 2 GeO 3 ‐based microwave dielectric ceramics with low permittivity

A low‐permittivity dielectric ceramic Li 2 GeO 3 was prepared by the solid‐state reaction route. Single‐phase Li 2 GeO 3 crystallized in an orthorhombic structure. Dense ceramics with high relative density and homogeneous microstructure were obtained as sintered at 1000‐1100°C. The optimum microwave dielectric properties were achieved in the sample sintered at 1080°C with a high relative density ~ 96%, a relative permittivity ε r ~ 6.36, a quality factor Q × f ~ 29 000 GH z (at 14.5 GH z), and a temperature coefficient of resonance frequency τ f  ~ −72 ppm/ ° C. The sintering temperature of Li 2 GeO 3 was successfully lowered via the appropriate addition of B 2 O 3 . Only 2 wt.% B 2 O 3 addition contributed to a 21.2% decrease in sintering temperature to 850°C without deteriorating the dielectric properties. The temperature dependence of the resonance frequency was successfully suppressed by the addition of TiO 2 to form Li 2 TiO 3 with a positive τ f  value. These results demonstrate potential applications of Li 2 GeO 3 in low‐temperature cofiring ceramics technology.