Synthesis of low expansion ceramics in lithia-alumina-silica system with zirconia additive using the powder precursor in the form of hydroxyhydrogel

Powder precursors lithium aluminosilicate (LAS) of low expansion characteristics were synthesized by following the wet interaction technique in the hydroxyhydrogel form using lithium carbonate (Li2CO3), hydrated aluminium nitrate [Al(NO3)(3)(.)9H(2)O], fume silica (SiO2) and zirconium oxychloride (ZrOCl(2)(.)8H(2)O). Dilatometry, X-ray diffraction (XRD), IR analysis, Scanning Electron Microscopy (SEM) and Image analysis were done to study sintering, characteristics phase transformation and microstructure on the sintered specimens. ZrO2 was found to promote the formation of beta-eucryptite, and grain size of the sintered specimens could be related to the amount of ZrO2 present in the starting powder precursor. The thermal expansion characteristics were also found to be strongly influenced by ZrO2 content in the specimens. (c) 2005 Elsevier Ltd and Techna Group S.r.l