Evolution of yttria nanoparticle ensembles

The formation of Y2O3 nanoparticles in precipitation from acidic nitrate aqueous solutions, which was done by regulating pH at the expense of their titration with an ammonium hydroxide aqueous solution, was studied. The jellylike precipitates of a (Y2(OH)5NO3 · nH2O, n = 2, 3) precursor lose their volatile components under heating and drying in several stages. Their chemical decomposition terminates at 500–550°C with the formation of the cubic modification of yttria. Yttria particles inherit the platelike morphology of the particles of their precursor. Under further heating, Y2O3 particles lose their nonequilibrium shape due to the decomposition of plates into roundish nanoparticles with the relief of mechanical stresses. The isothermal exposure of nanoparticles formed in this way leads to their stepped agglomeration with a sequential increase in the size of particles by an order of magnitude. The sintering of Y2O3 powders with the formation of ceramics was investigated.