A novel low-temperature sintering microwave dielectric ceramic Li4SrCaSi2O8 with low-ϵr and low loss

A novel low-temperature co-fired ceramic Li 4 SrCaSi 2 O 8 with orthogonal crystal system was synthesized at 860–940 °C by the conventional solid-state reaction. The dense ceramic Li 4 SrCaSi 2 O 8 features the excellent microwave dielectric properties : ϵ r  = 8.2, Q  ×  f  = 90,094 GHz and τ f  = −79.6 ppm/°C at 900 °C. Phillips–van Vechten–Levine (P–V–L) theory reveals that Si–O bond contributes 78.53% to the lattice energy for Li 4 SrCaSi 2 O 8 crystal, and it was concluded that the strong ionicity (79.9%) of the Si–O bond may be responsible for the low sintering temperature of the ceramic. By compounding with CaTiO 3 , a near zero τ f (−9.7 ppm/°C) and excellent comprehensive properties were obtained ( ϵ r  = 9.8, Q  ×  f  = 50,145 GHz) for 0.93Li 4 SrCaSi 2 O 8  + 0.07CaTiO 3 ceramic at 900 °C. The chemical compatibility was confirmed by co-fired with silver, proving that Li 4 SrCaSi 2 O 8 ceramic with small density is a promising candidate for LTCC dielectric materials .