Properties of LZS/nanoAl2O3 glass-ceramic composites

The LZS glass-ceramic (19.58 Li2O·11.10ZrO2·69.32SiO2) have a high coefficient thermal expansion (CTE) which can be a limitation in some applications. The addition of alumina in a LZS glass-ceramic matrix is able to reduce the CTE significantly. This happens because of the alumina affinity with respect to lithium silicates to form β-spodumene (LiAlSi2O6), a crystalline phase having a CTE nearly zero (0.9 × 10−6 °C−1). In this work, (1-5 vol%) Al2O3 nanoparticles (13 nm) were added to a LZS (3.5 μm) glass-ceramic matrix to prepare composites with the main goal of evaluation the influence of Al2O3 on their mechanical, thermal and electrical properties. Each composition was wet homogenized and then dried at 110 °C for 48 h for disaggregation. The composites, sintered at 900 °C for 30 min, with relative densities between 92% and 98%, showed zircon and β-spodumene as main crystalline phases. The incorporation of increasing additions of nanosized alumina progressively decreases the final density. This makes the properties to slightly decrease, also. The Young's modulus significantly decreases from 111 to 78 GPa of hardness due to the exponential variation with porosity, but the changes of toughness and hardness are much lower. The electrical conductivity was maintained within ±10-7 S·cm-1, and the dielectric constant ranged from 5 to 6 for all compositions. Thermal conductivity ranged around 4.2 to 3.5 W/mK.