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

A novel low-temperature co-fired ceramic Li4SrCaSi2O8 with orthogonal crystal system was synthesized at 860-940 degrees C by the conventional solid-state reaction. The dense ceramic Li4SrCaSi2O8 features the excellent microwave dielectric properties: Cr = 8.2, Q x f = 90,094 GHz and rf =-79.6 ppm/degrees C at 900 degrees C. Phillips-van Vechten-Levine (P-V-L) theory reveals that Si-O bond contributes 78.53% to the lattice energy for Li4SrCaSi2O8 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 CaTiO3 , a near zero rf (-9.7 ppm/degrees C) and excellent comprehensive properties were obtained (Cr = 9.8, Q x f = 50,145 GHz) for 0.93Li4SrCaSi2O8 + 0.07CaTiO3 ceramic at 900 degrees C. The chemical compatibility was confirmed by co-fired with silver, proving that Li4SrCaSi2O8 ceramic with small density is a promising candidate for LTCC dielectric materials.