Low temperature sintering and microwave dielectric properties of Ba3Ti5Nb6O28 with ZnO-B2O3 glass additions for LTCC applications

The effects of ZnB2O4 glass additions on the sintering temperature and microwave dielectric properties of Ba3Ti5Nb6O28 have been investigated using dilatometer, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and a network analyzer. The pure Ba3Ti5Nb6O28 system showed a high sintering temperature (1250 °C) and had the good microwave dielectric properties: Q × f of 10,600 GHz, ɛr of 37.0, τf of −12 ppm/°C. It was found that the addition of ZnB2O4 glass to Ba3Ti5Nb6O28 lowered the sintering temperature from 1250 to 925 °C. The reduced sintering temperature was attributed to the formation of ZnB2O4 liquid phase and B2O3-rich liquid phases. Also the addition of ZnB2O4 glass enhanced the microwave dielectric properties: Q × f of 19,100 GHz, ɛr of 36.6, τf of 5 ppm/°C. From XPS and XRD studies, these phenomena were explained in terms of the reduction of oxygen vacancies and the formation of secondary phases having the good microwave dielectric properties.