Phase Evolution and Properties of Li<sub>2</sub>O-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub>-Based Glass-Ceramic for LTCC Applications

Abstract

In this paper, the influences of sintering conditions on the phase transformation, microstructure, bulk density, bending strength, coefficient of thermal expansion, and dielectric properties of Li2O-Al2O3-SiO2 glass-ceramic were investigated. Conventional melt-quenching method was used to synthesize this glass-ceramic. Scanning electron microscopy, X-ray diffractometer and differential thermal analysis were employed to study this material. The XRD data show that Li2OAl2O37.5SiO2 is the main crystalline phase of this glass-ceramic. ZrO2 and CaMgSi2O6 are the two other phases in this glass-ceramic. The increasing sintering temperature and soaking time affect the phase composition obviously, which lead to the obvious variations of microstructure, mechanical, dielectric and thermal properties of this glass-ceramic. Sintering temperature and time play a key role in the sintering of Li2O-Al2O3-SiO2 glass-ceramic. The sample sintered at 800 °C for 30 min showed good microstructure, low sintering temperature of 800 °C, high density of ~2.6 g/cm3, excellent dielectric properties (εr: ~6.9, tan δ: ~2*10-3), good bending strength of 143 MPa and adjustable CTE from 1.1 to 2.7 *10-6 K-1 close that of silicon. These results mean that the obtained LAS glass-ceramic can be used in the application of LTCC substrate, especially, the manufacture of the substrate of silicon.