Temperature‐stable BaAl ₂ Si ₂ O ₈ –CaSnSiO ₅ microwave dielectric ceramics

Abstract In the present study, (1 − x )BaAl ₂ Si ₂ O ₈ − x CaSnSiO ₅ − y wt.% LiF microwave dielectric ceramics were prepared through the traditional solid‐state sintering at 950−1395°C for 5 h. The BaAl ₂ Si ₂ O ₈ phase could coexist with the CaSnSiO ₅ phase at (1 − x )BaAl ₂ Si ₂ O ₈ − x CaSnSiO ₅ (.2 ≤ x ≤ .6) ceramics, and no other secondary phase was observed. The CaSnSiO ₅ , as a τ _f regulator, adjusted the negative τ _f value of BaAl ₂ Si ₂ O ₈ to near zero. Excellent microwave dielectric properties ( ε _r = 8.1, Q × f = 37 560 GHz, and τ _f = −1.5 ppm/°C) were obtained from the 0.6BaAl ₂ Si ₂ O ₈ −0.4CaSnSiO ₅ ceramic. The sintering temperature of 0.6BaAl ₂ Si ₂ O ₈ −0.4CaSnSiO ₅ ceramic decreased from 1375°C to 950°C by introducing 2 wt.% LiF. The 0.6BaAl ₂ Si ₂ O ₈ −0.4CaSnSiO ₅ −2 wt% LiF ceramic exhibited remarkable microwave dielectric properties ( ε _r = 7.6, Q × f = 17 420 GHz, and τ _f = −12.2 ppm/°C) and could be applied to the low‐temperature co‐fired ceramic (LTCC) field.