SYNTHESIS OF NANOCRYSTALLINE AND MONODISPERSED PARTICLES OF CERAMICS THROUGH SOFT SOLUTION ROUTES

摘要

Crystalline ZnGa_2O_4 nanoparticles with a single phase of spinel were synthesized from a mixed solution of gallium sulfate and zinc sulfate in the presence of aqueous ammonia under hydrothermal conditions above 180℃in the pH range of 2.5 to 10. By treatment at 240℃for 50h, ZnGa_2O_4 spinel with the composition of ZnO/Ga_2O_3 =1 and a lattice parameter of a=0.83349 nm could be synthesized from the relatively concentrated solutions, e.g., 0.2 mol*dm~(-3) Ga_2(SO_4)_3, and Zn/2Ga =1.95. The diffusion of Zn~(2+) ions seemed to be the key for the synthesis and growth of the spinel for obtaining a stoichiometric composition. Monodispersed spherical CeO_2 particles composed of crystalline nanoparticles with a cubic fluorite structure could be synthesized from relatively concentrated Ce(IV) salt solutions up to 0.5 mol*dm~(-3) by forced hydrolysis above 150℃. Relatively dispersed CeO_2 nanoparticles were formed from the solutions without SO_4~(2-) ions. It was confirmed that the existence of SO_4~(2-) ions in acidified solution was a factor of consequence for the formation of the monodispersed secondary particles.