LZS/Al2O3 Glass-Ceramic Composites Sintered by Fast Firing

Abstract

In this work, nanometric Al 2 O 3 (1-5 vol.%) particles (13 nm, 100 m 2 /g) were added to a 19.58Li 2 O•11.10ZrO 2 •69.32SiO 2 (mol%) (3.5 µm, 2.5 m 2 /g) parent glass-ceramic matrix to prepare composites with the purpose of studying the influence of Al 2 O 3 on their structure, microstructure, mechanical, thermal and electrical properties when sintered by fast firing. The parent glass-ceramic was prepared by melting and fast cooling (in water) to obtain a glass frit. The resulting glass frit was milled according to a two-step procedure consisting on a dry milling stage followed by a long wet milling step down. Each composition was wet homogenized and then dried at 110 ºC for 48 h for disaggregation. The obtained powders were uniaxially pressed (100 MPa) and compacts sintered by fast firing (175 ºC/min) between 800 and 900 ºC for 30 min. The composites, with relative densities ranging from 89% to 93%, showed zircon and β-spodumene as main crystalline phases. The hardness and Young's modulus varied from 4.5 to 6.5 GPa, and from 65 to 102 GPa, respectively. The formation of β-spodumene in the obtained composites leads to reduce the CTEs, whose values ranged from 13 to 7 x 10 -6 ºC -1 .