CeO2 nano-precipitation in borosilicate glasses: A redox study using EELS

Precipitation of nanoscale phases in a series of five related alkali-borosilicate glasses is studied by scanning transmission electron microscopy and electron energy loss spectroscopy (EELS). All glasses studied are doped with 4 mol% of CeO2, and contain varying concentrations of other oxides to participate in possible redox interactions, including Fe2O3, Nd2O3, AgO, and Cr2O3. The particular precipitates found vary from droplet shaped amorphous to dendritic shaped single crystals. The oxidation state of Ce and the existence and morphology of Ce precipitates is found to depend on both cooling sequence and the presence of other oxides. One aim of the study is to explore and showcase the applicability of high spatial resolution fine structure EELS for the study of the interrelated phenomena of redox interaction, phase separation, solubility, and nanoscale crystallization.