left bracket (Li2O) multiplied by (times) (B2O3)2.

A blue color center appears in left bracket (LiO//2) multiplied by (times) (B//2O//3)//2 right bracket //1// minus //x left bracket WO//3 right bracket //x glasses for high WO//3 contents, x greater than equivalent to 0. 4. Details of the preparation for the occurrence of this center such as the WO//3 starting material, the temperature of the melt, the reaction time, and the influence of transition metals are systematically investigated, and the transmittance and its wavelength derivative of typical samples are presented as a function of quantum energy. In particular, a strong enhancement of the blue coloration by greater than equivalent to 200 ppm Co is observed while small amounts of Cu bleach the material. The results suggest that larger complexes H//xW//nO//3//n// minus //m already exist in the starting materials and persist for some time in the melt; cobalt apparently stabilizes these complexes.