Low‐temperature sintering and thermal stability of Li2GeO3‐based microwave dielectric ceramics with low permittivity

• Published in: Journal of the American Ceramic Society 2018-10, Vol.101 (10), p.4608-4614
• Main Authors: Yin, Changzhi, Xiang, Huaicheng, Li, Chunchun, Porwal, Harshit, Fang, Liang
• Format: Article
• Language: English
• Subjects: Boron oxides; Ceramics; Crystallization; Density; Dielectric properties; Li2GeO3; Low temperature; LTCC; microwave dielectric properties; Permittivity; Q factors; Sintering; Temperature dependence; Thermal stability; Titanium dioxide
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.15723

A low‐permittivity dielectric ceramic Li2GeO3 was prepared by the solid‐state reaction route. Single‐phase Li2GeO3 crystallized in an orthorhombic structure. Dense ceramics with high relative density and homogeneous microstructure were obtained as sintered at 1000‐1100°C. The optimum microwave dielectric properties were achieved in the sample sintered at 1080°C with a high relative density ~ 96%, a relative permittivity εr ~ 6.36, a quality factor Q × f ~ 29 000 GHz (at 14.5 GHz), and a temperature coefficient of resonance frequency τf ~ −72 ppm/°C. The sintering temperature of Li2GeO3 was successfully lowered via the appropriate addition of B2O3. Only 2 wt.% B2O3 addition contributed to a 21.2% decrease in sintering temperature to 850°C without deteriorating the dielectric properties. The temperature dependence of the resonance frequency was successfully suppressed by the addition of TiO2 to form Li2TiO3 with a positive τf value. These results demonstrate potential applications of Li2GeO3 in low‐temperature cofiring ceramics technology.