DEPLETION OF HIGH-ENERGY CARRIERS IN YAG OPTICAL CERAMIC MATERIALS

The scintillation properties of YAG:Ce transparent ceramic material pr epared by a hot-pressing technique have been characterized and compare d with those of a chemically identical specimen of single crystal. Eac h of the scintillation steps (conversion, energy transfer and luminesc ence) has been selectively investigated using appropriate spectroscopi c techniques. The light output from the ceramic specimen was measured at approximate to 1500 photons/MeV, only 10% of that from the single c rystal. This drastic decrease in the ceramic reflects the inefficient transfer of energy from the excited host to the Ce ion. The inefficien cy can be attributed to the presence in the ceramic material of a high population of lattice defects, as demonstrated by the UV absorption s pectra. Thermoluminescence experiments show that these defects can ser ve as sinks for free carriers (electrons and holes), providing sites f or their nonradiative recombination and preventing them from conveying their energy to the emitting centers. (C) 1998 Elsevier Science B.V. All rights reserved.