Enhanced quality factor of zinc lanthanum borates-based dielectrics via the control of ZnO/B₂O₃ ratio

A dielectric system having an exceptionally high-quality factor of 1350 at 16.8 GHz is reported as a strong candidate for glass-based low-temperature cofireable materials. The dielectrics are based on unusual (16-27) ZnO·16La₂O₃·(57-68)B₂O ₃ glass mixed with a fixed 50 wt% Al₂O₃ filler. The ratio of ZnO/B₂O₃ was found to be critical in controlling the nature of glass and, consequently, performance of the dielectric mixture. For example, 27ZnO·16La₂O₃· 57B₂O₃ glass sample having the highest Zn content resulted in the lowest softening temperature of 647°C and the least porosity of ∼6%. The enhanced densification and extensive crystallization of low loss phases, i.e., LaAl_2.03(B₄O₁₀)O_0.54 and ZnAl₂O₄, are assumed to be responsible for better dielectric performance that resulted from the increase of Zn content in glass.