Interaction of Ce1−xErxO2−y nanoparticles with SiO2-effect of temperature and atmosphere

Morphology, microstructure and phase evolution of homogeneous, nanocrystalline Ce1−xErxO2−x/2 mixed oxide (x=0.3 and 0.5), prepared by microemulsion method, supported on amorphous SiO2 was studied in oxidizing and reducing atmosphere by XRD, TEM, SEM-EDS and N2 adsorption. The system is structurally and chemically stable in the oxidizing atmosphere up to 1000 °C, exhibiting only a small increase of the mean crystallite size of the oxide to ∼4 nm. At 1100 °C formation of Er silicate with unusual structure isomorphic with y-Y2Si2O7 (yttrialite), stabilized by Ce4+ ions was observed. In the reducing atmosphere the Ce1−xErxO2−x/2 reacted with SiO2 already at 900 °C, due to high affinity of the reduced Ce3+ to form a silicate phase. At higher temperature the silicate crystallized into the tetragonal, low temperature A-(Ce1−xErx)2Si2O7 polymorph. Such systems, containing nanocrystalline silicate particles with Er3+ ions placed in well defined sites embedded in silica matrix, may be interesting as highly efficient active components of optical waveguides amplifiers integrated with Si microelectronics. The nanocrystalline Ce–Er–O/SiO2 system prepared by the impregnation of the silica with the aqueous solution of nitrates appeared to be chemically inhomogeneous and less stable in both oxidising and reducing atmosphere. - Graphical abstract: Structure evolution of Ce0.5Er0.5O1.75 in air and in H2. Display Omitted - Highlights: • Homogeneous 3 nm Ce1−xErxO2−y particles were prepared and uniformly dispersed on SiO2. • Er diffusion to SiO2 determines the stability of the mixed oxide in air to ∼1000 °C. • Spreading of Ce1−xErxO2−y onto SiO2 occurs in hydrogen at 900 °C. • Nanocrystalline A-(Ce,Er)2Si2O7 silicate forms in H2 at 1100 °C