Low-temperature sintering and microwave dielectric properties of ZnGa2–xO4–1.5x ceramics with added B2O3

In this work, ZnGa 2– x O 4–1.5 x (0.0 ≤  x  ≤ 0.15) ceramics were synthesized by a solid-state reaction method. ZnGa 2 O 4 ceramic that is sintered at 1300 °C/3 h exhibits good microwave dielectric properties with ε r of 11.06, Q  ×  f of 74,730 GHz, and τ f of − 69.7 ppm/°C. However, it cannot be fully densified at temperatures lower than 960 °C, even when a large amount of B 2 O 3 is added, which seriously inhibits its application in the LTCC (low temperature cofired ceramic) field. Therefore, adding B 2 O 3 to Ga 2 O 3 -deficient ZnGa 2 O 4 ceramics is proposed to decrease the sintering temperature to below 960 °C. Owing to the dual effect of the B 2 O 3 -rich and ZnO-B 2 O 3 related liquid phases, ceramics with added B 2 O 3 (≥ 20 mol%) were found to sinter well at 950 °C, and good microwave dielectric properties were also achieved. In particular, 25 mol% B 2 O 3 added to ZnGa 1.95 O 3.925 ceramic sintered at 950 °C showed promising microwave dielectric properties for 5 G/6 G technologies without reaction with a silver electrode: ε r  = 9.19, Q  ×  f  = 37,337 GHz, and τ f  = − 58.3 ppm/°C.