Sol&nda
sh;gel gla
ss matrice
s containing lanthanide
s have numerou
s technological application
s and their formation involve
s several chemical facet
s. In the ca
se of cerium, it
s ability to exi
st in two different oxidation
state
s or in mixed valence
state provide
s additional complexitie
s for the
sol&nda
sh;gel proce
ss. The oxidation
state of cerium pre
sent during different facet
s of preparation of
sol&nda
sh;gel gla
sse
s, and al
so a
s a function of the
starting oxidation
state of cerium added, were
studied both by optical
spectro
scopy and X-ray ab
sorption near-edge
structure
s (XANES). The finding
s acquired by each approach were compared. The primary focu
s wa
s on the redox chemi
strie
s a
ssociated with
sample preparation, gelation, and thermal treatment. When Ce
3+ i
s introduced into the
starting
sol
s, the trivalent
state normally prevail
s in the wet and room temperature-dried gel
s. Heating in air at >100°C can generate a light yellow coloration with partial oxidation to the tetravalent
state. Above 200°C and up to
![](/image<font)
s/glyph
s/BQ1.GIF>1000°C, cerium i
s oxidized to it
s tetravalent
state. In contra
st, when tetravalent cerium i
s introduced into the
sol, both the wet and room temperature-dried gel
s lo
se the yellow&nda
sh;brown color of the initial ceric ammonium nitrate
solution. When the
sol&nda
sh;gel i
s heated to 110°C it turn
s yellowi
sh a
s the cerium tend
s to be re-oxidized. The yellow color i
s believed to repre
sent the effect of oxidation and oligomerization of the cerium&nda
sh;
silanol unit
s in the matrix. The lumine
scence propertie
s are al
so affected by the
se change
s, the detail
s of which are reported herein.