Effects of MgO on properties of Li2O–Al2O3–SiO2 glass–ceramics for LTCC applications

Abstract

Li2O–Al2O3–SiO2 (LAS) glass–ceramics for low temperature co-fired ceramics (LTCC) application were prepared by melting method, and the effects of MgO on the sinterability, microstructure, dielectric property, thermal expansion coefficient (CTE) and mechanical character of this glass–ceramics have been studied. The X-ray diffraction images represent that the main phase is β-spodumene solid solutions. And some ZrO2 and CaMgSi2O6 phases in LAS glass–ceramics are detected. The LAS glass–ceramics without additive (MgO) sintered at 800° had the dielectric properties: dielectric constant (er) of 5.3, dielectric loss (tanδ) of 2.97 × 10−3 at 1 MHz, CTE value of 1.06 × 10−6 K−1, bulk density of 2.17 g/cm3, and flexural strength of 73 MPa. 5.5 wt% MgO-added LAS glass–ceramic achieves densification at 800° exhibited excellent properties: low dielectric constant and loss (er = 7.1, tanδ = 2.02 × 10−3 at 1 MHz), low CTE (2.89 × 10−6 K−1), bulk density = 2.65 g/cm3 as well as high flexural strength (145 MPa). The results indicate that the addition of MgO is helpful to improve the dielectric and mechanical properties. The formation of CaMgSi2O6 crystal phase with higher CTE leads to the increase of CTE value of LAS glass–ceramics due to the increasing MgO content, and the increase of CTE is favourable for matching with silicon (3.1 × 10−6 K−1). The prepared LAS glass–ceramics have the potential for LTCC application.