Improved microwave dielectric properties of Mg₄Nb ₂O₉ ceramics with CaO-B₂O₃-SiO ₂ glass additions

The effects of CaO-B₂O₃-SiO₂ (CBS) glass addition on the sintering temperature and dielectric properties of Mg ₄Nb₂O₉ ceramics have been investigated using X-ray diffraction, Scanning electron microscopy and Differential thermal analysis. The CBS glass can change to liquid phase at about 750 C and a small amount of CBS glass addition to Mg₄Nb₂O₉ ceramics can greatly decrease the sintering temperature to about 1,125 C. It is revealed that the reduced sintering temperature is attributed to the formation of liquid phase. The major phases of the sample are Mg₄Nb ₂O₉ and MgNb₂O₆. The relationship between τ _f values and the content of glass additions have the reverse change trends. The Mg₄Nb₂O₉ ceramics with 2wt% glass addition sintered 1,125 C exhibit good microwave dielectric properties: dielectric constant (ε _r ) of 13 and Q·f value of 69,000 GHz.