Microwave properties and structure of La-Ti-Si-B-O glass-ceramics for applications in GHz electronics

A dielectric bulk glass-ceramic of the La2O3-TiO2-SiO2-B2O3 system is developed which is able to fulfill the requirements for dielectric loading-based mobile communication technologies. It is shown that the given dielectric requirements can be fulfilled by glass-ceramic materials without being dependent on ceramic processing techniques. The material exhibited permittivity values of 20 < ɛr < 30, quality factor 2000 GHz < Qf < 10,000 GHz and a temperature coefficient of resonance frequency −100 < τf < +180 ppm/K. A zero τf material with a Qf value of 9500 GHz and ɛr = 21.4 could be achieved at a ceramming temperature Tcer = 870 °C. The material is aimed to provide an alternative to existing, commercially used sintered ceramic materials. Further focus is laid on the investigation of the dominant dielectric loss mechanisms in the GHz frequency range and how they are correlated with the microstructure.