Color Centers in a Cerium-Containing Silicate Glass

X-ray irradiation of glass with the weight percent composition 75% SiO2, 25% Na2O produces color centers which absorb visible light. Cerium in the glass prevents the formation of these centers. The nature of the centers and the mechanism by which cerium prevents their formation are studied by measuring the optical absorption changes caused by irradiation of glasses containing small concentrations of Ce3+ and Ce4+. The conclusions are: In cerium-free glass, trapped holes cause optical absorption bands with maxima near 4400 and 6200 Å. By capturing holes, Ce3+ inhibits the formation of these two bands. The probability that a hole escapes capture by Ce3+ is exp (—v3c3), where c3 is the Ce3+ concentration and v3=(9±2) × 104 Å3. Trapped electrons cause an optical absorption band that has a maximum in the uv and that extends to 6000 Å in the visible. Ce4+ inhibits the formation of this band by capturing electrons.