Microwave dielectric properties of glass-ceramic composites for low temperature co-firable ceramics

Ba–B–Si glass was added to Ba–Nd–Sm–Bi–Ti–O (BRT114) microwave dielectric material for LTCC applications. Conventional one-step processing method for preparing glass-BRT114 composite materials yields low dielectric constant, since the glass was easy to react with BRT114 and forms a low dielectric constant phase, Ba3B6Si2O16. A large proportion of pores appeared. The nature of glass, whether it is sol-gel derived or fused, shows marked influence on the microstructure and microwave dielectric properties of the composites. A two-step process containing precoating the BRT114 powders with a thin layer of glass, followed by conventional samples preparation process, tremendously improved the densification behaviour of the material. The formation of pores and interactions between glass and BRT114 was greatly suppressed such that materials with high dielectric constant (εr=40) were achieved by sintering 9 wt.% glass-containing composite at 950 °C for 2.5 h.