POWDER SYNTHESIS, CHARACTERIZATION AND SINTERING BEHAVIOR OF LITHIUM TITANATE

摘要

A comparative study of the sintering behavior of the lithium titanate (Li_2 TiO_3) powders formed by combustion of the nitrate (lithium and titanium)-glycine gel (powder-A) and reaction of the mixture of lithium carbonate with titania (powder-B) was carried out. The calcination temperature to form chemically pure and nano-crystalline powders as obtained by DTA- TG and XRD was found to be 600°C for powder -A and 750°C for powder-B. The dry ground powders contained coarse agglomerates and were wet ground under an optimized dispersion condition (pH ~9, solid content 20wt.%). The agglomerate size of the ground slurries were ~0.6μm for powder -A and ~2.6um for powder-B. A study of the shrinkage behavior by dilatometry exhibited better sinter-ability for powder -A. A detailed study of the pore size distribution in the green compacts by mercury intrusion porosimetry revealed that the compacts from powder-A exhibit finer size distribution (average size ~0.1 μm) than the compacts from powder-B ((average size ~0.4μm) even though their green compact densities were in the range of 50 to 55%T.D. After sintering at a temperature of 1100°C for 2hrs, compacts of powder-A and powder-B exhibited a sintered density of 92 and 78% T.D. respectively. The difference in sintering behavior of the two powders was correlated to the difference in the pore size distribution in the green compact and its evolution during heating.