Hard Radiation Detection from the Selenophosphate Pb2P2Se6

The heavy metal selenophosphate, Pb2P2Se6, is a promising new material for cost-effective X-ray/-ray detection. Crystal boules of Pb2P2Se6 up to 25 mm in length and 15 mm in diameter are grown by a vertical Bridgman method. They are cut and processed into size-appropriate wafers for physical, photo-transport property studies, as well as -ray detector testing. The material is a semiconductor with an indirect bandgap of 1.88 eV and has electrical resistivity in the range of 1 x 10(10) cm. Pb2P2Se6 single crystal samples display a significant photoconductivity response to optical, X-ray, and -ray radiation. When tested with a Co-57 -ray source, Pb2P2Se6 crystals show spectroscopic response and several generated pulse height spectra resolving the 122.1 and 136.5 keV Co-57 radiation. The mobility-lifetime product of Pb2P2Se6 is estimated to be approximate to 3.5 x 10(-5) cm(2) V-1 for electron carriers. The Pb2P2Se6 compound melts congruently at 812 degrees C and has robust chemical/physical properties that promise low cost bulk production and detector development.