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

• Published in: Ceramics international Vol. 49; no. 13; pp. 22617 - 22622
• Main Authors: Du, Qianbiao, Wen, Quanzhang, Jiang, Longxiang, Liu, Shucheng, Ma, Linzhao, Li, Hao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2023
• Subjects: Li4SrCaSi2O8; LTCC; Microwave dielectric properties; Phillips–van Vechten–Levine (P–V–L) theory; LTCC; Li4SrCaSi2O8; Phillips–van Vechten–Levine (P–V–L) theory; Microwave dielectric properties
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2023.03.306

A novel low-temperature co-fired ceramic Li4SrCaSi2O8 with orthogonal crystal system was synthesized at 860–940 °C by the conventional solid-state reaction. The dense ceramic Li4SrCaSi2O8 features the excellent microwave dielectric properties: ϵr = 8.2, Q × f = 90,094 GHz and τf = −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 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 τf (−9.7 ppm/°C) and excellent comprehensive properties were obtained (ϵr = 9.8, Q × f = 50,145 GHz) for 0.93Li4SrCaSi2O8 + 0.07CaTiO3 ceramic at 900 °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.