Influences of ZrO₂ on microstructures and properties of Li₂O–Al₂O₃–SiO₂ glass–ceramics for LTCC applications

In this work, Li₂O–Al₂O₃–SiO₂ (LAS) glass–ceramics for LTCC applications were prepared by the melt quench technique, and the influences of ZrO₂ content on the microstructure, thermal, mechanical and electrical properties were investigated. XRD showed that the major crystalline phase was Li₂OAl₂O₃7.5SiO₂ and the minor crystalline phases were ZrO₂ and CaMgSi₂O₆. The formation of ZrO₂ crystal phase with higher coefficient of thermal expansion (CTE) led to the increase of CTE value of LAS glass–ceramics, which was favorable for matching with silicon (3.1 × 10⁻⁶/°C). Moreover, it was found that the mechanical property enhanced markedly when the high thermal expansion phases generated in the glass–ceramic system with low CTE. The results indicated that the addition of ZrO₂ was beneficial to promote the mechanical, thermal and dielectric properties. 3 wt% ZrO₂-added LAS glass–ceramic sintered at 800 °C exhibited excellent properties: a high bulk density of 2.567 g/cm³, a high linear shrinkage of 20.08 %, a low CTE value (2.68 × 10⁻⁶/°C), a high flexural strength of 157 MPa, a low dielectric constant of 7.1, a low dielectric loss (tan δ) of 1.884 × 10⁻³ at 1 MHz, and a high resistivity (ρ > 10¹⁰ Ω cm).