Effects of phase and chemical composition of precursor on structural and morphological properties of (Lu0.95Eu0.05)2O3 nanopowders

Europium-doped lutetium oxide nanopowders have been synthesized by the co-precipitation technique using ammonium hydrogen carbonate as a precipitant. Effects of chemical and phase composition of carbonate precursors on the morphology and sinterability of (Lu0.95Eu0.05)2O3 nanopowders have been studied. Two types of precursors have been obtained differing by the molar ratio R=NH4HCO3/Lu3+: a mixture of crystalline Lu0.95Eu0.05(OH)(CO3)·4H2O and unidentified amorphous phases at R=4-7 and crystalline Lu0.95Eu0.05(H2O)x(HCO3)3·nH2O precursor at R=8-20. The two-phase precursor consists of spherulite-like aggregates, while the crystalline one is characterized by plate-like morphology. Calcination of Lu0.95Eu0.05(H2O)x(HCO3)3·nH2O leads to formation of (Lu0.95Eu0.05)2O3 nanopowders that inherit the precursor morphology, while no morphology succession is observed for (Lu0.95Eu0.05)2O3 nanopowders obtained by heat treatment of the two-phase precursor. Calcination of the two-phase mixture leads to breakdown of the spherulites and to formation of equiaxed particles with an average diameter of 40 nm with the standard deviation of particle size distribution of about 15%. The obtained low-agglomerated nanopowders were used in vacuum sintering to produce (Lu0.95Eu0.05)2O3 optical ceramics with in-line transmittance of 41% at 611 nm.