Zone center phonon frequencies in tetragonal zirconia: lattice dynamical study and new assignment proposition

Two synthesis routes, sol precipitation and sol gelation, using aluminum isopropoxide and lithium nitrate as precursors have been used to prepare lithium aluminate. The sol precipitation method (LISOL) produced a mixture of (gamma)-LiAlO2 and LiAl5O8, and sol gelation (LIGEL) produced pure (gamma)-LiAlO2, both at 750°C. The density and specific surface area of the ceramic powders calcined at 1150°C were 2.72gcm-3 and 6m2g-1, respectively, for the powders obtained by sol precipitation and 2.47gcm-3 and 2m2g-1, respectively, for the powders obtained by sol gelation. The synthesized powders presented thermal stability over 600°C and the sintering process occurred in the temperature range of 600-1400°C. The absorbed heat by the material in this temperature range during DTA/TG experiment showed that the sintering process was more efficient when the powders were previously calcined over 550°C.