X-RAY AND ULTRAVIOLET LUMINESCENCE OF Li3Ta1-xNbxO4 PREPARED BY FLUX SYNTHESIS AND CHARACTERIZATION OF A NEW HIGH EFFICIENCY X-RAY PHOSPHOR

摘要

The phase development and luminescence properties, under both X-ray and uv excitation, of the lithium orthotantalate-lithium orthoniobate system, Li3Ta1-xNbxO4 for x=0 to 1, were examined. Using a flux synthesis technique, it was found that the levels of Nb doping in monoclinic Li3TaO4 and of Ta doping in cubic Li3NbO4 are higher than previously reported. Under 30 kVp Mo X-ray excitation, Li3Ta1-xNb4O4 is an efficient blue-emitting phosphor with broadband emission, peaking in the range of 390 to 435 nm. For x=0 to 0.1, the overall luminescence efficiency is comparable to, or better than, a commercial calcium tungstate, CaWO4, Hi-Plus material. The composition Li3Ta0.995Nb 0.005O4 demonstrates an overall luminescence efficiency that makes this phosphor 45% brighter than CaWO4 Hi-Plus. Under uv excitation, broadband blue emission is also observed. For all the Li3Ta1-xNbxO4 (x>0) solid solutions, the emission peak maximums agree well with those seen under X-ray excitation and are the result of Nb5+ emission. 13 refs.