Particle size modulation for effectively optimizing the dielectric and mechanical properties of La2O3–B2O3 based glass-ceramic/ceramic LTCC substrates

Abstract

Lanthanum borate-based glass-ceramic has recently received considerable attention in the field of high-frequency communications as a sintering aid, due to the low sintering temperature and the precipitation of crystalline phases with excellent dielectric and mechanical properties. Importantly, the densification and crystallization behaviors of glass-ceramic are not only determined by its composition, but also affected by various processing parameters, such as the initial particle size, which is rarely explored for optimizing the dielectric and mechanical properties of lanthanum borate-based glass-ceramic/ceramic composites. Herein, La2O3–B2O3–CaO–P2O5–SiO2 (LBCPS) glass-ceramics with a series of initial particle sizes are achieved by ball milling method through controlling the milling time. Employing LBCPS glass-ceramics with different particle sizes as the sintering aid, various LBCPS/Al2O3 composites are fabricated, and the dielectric and mechanical properties of which are further investigated. Notably, the LBCPS/Al2O3 composite with a moderate glass-ceramic particle size of 2.7 μm exhibits the excellent comprehensive performance with a low dielectric loss of 8.6 × 10−4 at 9.8 GHz and a high flexural strength of 199 MPa. Moreover, the influencing mechanisms of the glass-ceramic particle size on the crystallization, microstructure, and densification of the LBCPS/Al2O3 composite have also been systematically explored and proposed. This research work provides an intriguing strategy for optimizing the dielectric and mechanical properties of the glass-ceramic/ceramic as the high-performance low-temperature co-fired ceramic (LTCC) substrate.