Weakening the silicate network through six-coordinated magnesium to achieve a high degree of crystallization of β-CaSiO3 in calcium borosilicate glass ceramics for 5G application

Abstract

β-CaSiO3 with a low dielectric constant and low dielectric loss is one of the decisive components of commercial calcium borosilicate (CBS) low-temperature co-fired ceramic substrate. However, achieving a high degree of crystallization of β-CaSiO3 is difficult in CBS glass ceramics because of the competitive multiphase crystallization during sintering. We have shown that six-coordinated magnesium can be used to weaken the silicate network to achieve a high degree of crystallization of β-CaSiO3 in CBS glass ceramics. The appropriate MgO content to ensure a large amount of MgO6 production gradually destroys the [SiO4] tetrahedral network as the temperature increases, resulting in a β-CaSiO3 content of 76.2 vol%, when the MgO content is 2.71 mol%. The resulting material has the lowest dielectric constant (4.95@15 GHz) and dielectric loss (8 × 10−4@15 GHz), and the best three-point bend strength (77.43 MPa). Our work provides an effective method of changing the crystallization by modifying the glass network in silicate-based glass ceramics with a low dielectric constant.