ABSTRACT
In the present study, the sol-gel method has been simplified for the synthesis of high-tech mixed-oxide silicate powders by the modification of existihg method. Water was used as the common solvent for the starting materials for the synthesis of multi-component silicate gel powders. This method is therefore termed as "aqueous sol-gel method".
i
Tetraethoxysilane was used as the starting material for the silica component. Metal formates or oxalates were used as the starting materials for the corresponding metal oxide components, preparation of gels of the following silicate systems have been performed:- (i) Zr02~Si02 , (ii) mullite(2Si02 .3A1203 ), (iii) cordierite (2MgO.2A120 3 .5Si02) and
(iv) cordierite-zirconia composite. Gels were dried and ground to powder, and calcined at different temperatures in the range 600° to 1300°C. The dried &nd calcined powders were characterised by thermogravimetric analysis, differential thermal analysis, X-ray powder diffrabtion, infrared spectra, scanning electron microscope and BET surface area analysis.
Another simple, cost effective and versatile chemical route has been developed for the preparation of any desired mixed-oxide systems at a fairly low temperature. The process involves rapid evaporation of polyvinyl alcohol(PVA)-added mixed metal nitrate solution followed by calcination of the evaporated mass. This method is termed as "PVA-solution method". A series of mixed-oxide systems including calcia- and yttria-stabilised zirconia, and lanthanum modified lead
xi
zirconate tita'nate were prepared and studied systematically with the help of standard physical techniques.
KEY WORDS: CERAMIC POWDERS, CHEMICAL SYNTHESIS, MIXED-OXIDE, HIGH-TECH, AQUEOUS SOL-GEL, PVA-SOLUTION, MULLITE, CORDIERITE, STABILISED ZIRCONIA, PLZT.
