Effect of phosphorus on the structural nonhomogeneity and dielectric properties of alkaline earth aluminoborosilicate glasses

Abstract

Alkaline earth borosilicate glass with excellent dielectric properties and matching coefficient of thermal expansion is a promising material for glass core substrates. It is vital to understand the effect of P₂O₅ on the network structure and dielectronic properties of alkaline earth aluminoborosilicate glasses (nP₂O₅-(1-n)[9.4CaO-4.9MgO-11.6Al₂O₃–21.7B₂O₃–52.5SiO₂] mol%, n = 0–0.06) for development of the next generation of dielectric glass substrates for electronics. Interestingly, our data indicate that when P₂​O₅​ < 3 mol%, both the dielectric constant (ε_r) and dielectric loss (tanδ) decrease, whereas both ε_r​ and tanδ increase with P₂​O₅  > 3 mol%. These results suggest that the moderate loading of P₂​O₅​ induces inhomogeneity in the network, ultimately leading to changes in the trends of both the dielectric constant and dielectric loss in the system. The former results in the inhomogeneity of silicate network structure due to the formation of P-O-Al bonds, while the latter results in loose structure due to the appearance of pyrophosphate structure. The sample with 3 mol% P₂O₅ exhibits optimal dielectric properties, ε_r 4.10 and tanδ 1.60 × 10⁻⁴ at 1MHz, CTE 3.4 × 10⁻⁶ K⁻¹ at 300K matching with the silicon wafer, plus excellent VH 567 kgf/mm². The thermal expansion coefficient and microhardness are mainly affected by the oxygen environment in the glass network. Our research provides a theoretical basis for the development of low-dielectric glasses.