Creating Single-Crystalline β-CaSiO3 for High-Performance Dielectric Packaging Substrate

beta-CaSiO3 based glass-ceramics are among the most reliable materials for electronic packaging. However, developing a CaSiO3 glass-ceramic substrate with both high strength (>230 MPa) and low dielectric constant (<5) remains challenging due to its polycrystalline nature. The present work has succeeded in synthesizing single-crystalline beta-CaSiO3 for a high-performance glass-ceramic substrate. This is accomplished by introducing Al3+ into the CaO-B2O3-SiO2 glass system, and by optimizing the sintering condition. Al3+ doping facilitates a heterogeneous network structure that energetically favors the precipitation of polycrystalline particles, including nanosized beta-CaSiO3 crystals and sub-nanosized alpha-CaSiO3 crystals. As the sintering temperature increases, the nano alpha-CaSiO3 crystals (2-10 nm) are gradually absorbed by the beta-CaSiO3 crystals. Through atomic rearrangement, alpha-CaSiO3 crystals transform into micrometer-sized single crystal beta-CaSiO3 (1-2 <mu>m) with layered structure. The low temperature co-fired beta-CaSiO3 glass-ceramics exhibit exceptional properties, including a low dielectric constant of 4.04, a low dielectric loss of 3.15 x 10(-3) at 15 GHz, and a high flexural strength of 256 MPa. This work provides a new strategy for fabricating high-performance single-crystalline glass-ceramics for electronic packaging and other applications.