Christian SALLÉ, Alexandre MAÎTRE, Jean-François BAUMARD, and Yoël RABINOVITCH¹

Laboratoire Science des Procédés Céramiques et de Traitements de Surface, Universitéde Limoges, UMR CNRS n°6638, 123 Avenue Albert Thomas, 87060 Limoges Cedex, France
¹Compagnie Industrielle des Lasers, Bâtiment Ester, BP 76923, 87069 Limoges Cedex, France

(Received March 15, 2007; Accepted June 8, 2007)

The effect of silica addition on the sintering of yttrium aluminium garnet doped by neodymium (Nd:YAG) was investigated on the basis of microstructural and thermal characterizations as well as of chemical analysis. The samples were sintered under secondary vacuum at temperatures ranging from 1473 to 1973 K. The role of silica, added as a sintering aid, appears significant between 1673 and 1873 K when high silica contents have been introduced in reactive mixtures. The positive effect of the silica phase on densification is linked to the appearance of secondary phases issued from reactions with the YAG matrix phase. In particular, two main secondary phases have been detected. One is a silica-rich phase which prevails at lower temperatures while the second possesses a more complex composition. When the sintering temperature increases, the composition of the latter phase evolves in the ternary SiO₂–Y₂O₃–Al₂O₃ system near the eutectic compositions, the melting point of which could lie in the vicinity of 1673 K. It is then suggested that sintering occurs via a liquid phase.

Key words: YAG, reactive and pressureless sintering, silica, fusible secondary phase