Influences of glass content on the microstructure and properties of BaO-CaO-Al2O3-SiO2 glass/alumina composite for LTCC applications

In this paper, a new amorphous Ba-Ca-Al-Si glass was prepared and the composites with different glass/alumina ratios, which ranged from 40 wt. % glass to 60 wt. % glass, have been studied. According to XRD patterns, the main crystalline phases of the composites are Al2O3 and BaAl2Si2O8, and BaAl2Si2O8 is generated by the reaction between glass and alumina. With regard to dielectric and mechanical properties, both the dielectric constant and the bending strength of the samples show positive relationships with glass content, and then the values tend to decline when the glass content exceeds 55 wt. %, which can be explained by the results of sintering shrinkage curves, bulk densities and SEM images. The optimal composition of 55 wt. % glass-45 wt. % alumina was developed, exhibiting good dielectric properties (εr=5.882, tanδ=2.75× 10-3) and high bending strength (σ=169 MPa). Finally, the 55 wt. % glass/alumina composite was chosen for tape casting, showing a well chemical compatibility with silver.