Identifying semiconductors by D.C. ionization conductivity

We describe a method for identifying semiconductor radiation detector materials based on the mobility of internally generated electrons and holes. It was designed for the early stages of exploration, when samples are not available as single crystals, but as crystalline powders. Samples are confined under pressure in an electric field and semiconductors are identified by an increase in d.c. conductivity during exposure to a high-intensity source of /sup 60/Co gamma rays. Using this method, we have determined that BiOI, PbIF, BiPbO/sub 2/Cl, BiPbO/sub 2/Br, BiPbO/sub 2/I, Bi/sub 2/GdO/sub 4/Cl, Pb/sub 3/O/sub 2/I/sub 2/, and Pb/sub 5/O/sub 4/I/sub 2/ are semiconductors.