PREPARATION OF HIGH-PURITY ZRSIO4 POWDER USING SOL-GEL PROCESSING AND MECHANICAL-PROPERTIES OF THE SINTERED BODY

Effects of the concentration of ZrOCl2, calcination temperature, heating rate, and the size of secondary particles after hydrolysis on the preparation of high-purity ZrSiO4 fine powders from ZrOCl2.8H2O (0.2M to 1.7M) and equimolar colloidal SiO2 using sol-gel processing have been studied. Mechanical properties of the sintered ZrSiO4 from the high-purity ZrSiO4 powders have been also investigated. Single-phase ZrSiO4 fine powders were synthesized at 1300-degrees-C by forming ZrSiO4 precursors having a Zr-O-Si bond, which was found in all the hydrolysis solutions, and by controlling a secondary particle size after hydrolysis. The conversion rate of ZrSiO4 precursor gels to ZrSiO4 powders from concentrations other than 0.4M ZrOCl2.8H2O increased when the heating rate was high, whereupon the crystallization of unreacted ZrO2 and SiO2 was depressed and the propagation and increase of ZrSiO4 nuclei in the gels were accelerated. The density of the ZrSiO4 sintered bodies, manufactured by firing the ZrSiO4 compacts at 1600-degrees to 1700-degrees-C, was more than 95% of the theoretical density, and the grain size ranged around 2 to 4-mu-m. The mechanical strength was 320 MPa (room temperature to 1400-degrees-C), and the thermal shock resistance was superior to that of mullite and alumina, with fairly high stability at higher temperatures.