Synthesis of controlled semiconductors

When studying the color of rutile, a project sponsored by the Geophysics Branch of the O.N.R., W. A. Weyl and T. Forland∗ discovered that the blue-grey color which is characteristic for partly reduced rutile may be obtained in an oxidizing atmosphere if an occasional Ti
⁴⁺
ion is replaced by a cation of a valency higher than four (Sb
⁵
+, Cb
⁵⁺
, W
⁶⁺
).