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

• 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.

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.

Structure evolution of Ce0.5Er0.5O1.75 in air and in H2.Figure optionsDownload as PowerPoint slide