TOP-SEEDED SOLUTION GROWTH OF LUTETIUM PHOSPHATE FROM POTASSIUM PYROPHOSPHATE FLUX

NEW DETECTOR MATERIALS ARE REQUIRED FOR THE DESIGN OF NEW AND IMPROVED POSITRON EMISSION TOMOGRAPHY INSTRUMENTS THAT WOULD OFFER HIGHER RESOLUTION AND BETTER SENSITIVITY IN NON-INVASIVE MEDICAL APPLICATIONS. CURRENTLY, BISMUTH GERMANIUM OXIDE IS ONE OF THE MOST POPULAR SCINTILLATOR MATERIALS BEACUSE OF ITS RELATIVELY GOOD PROPERTIES AND LOW COST. RECENTLY, CERIUM-DOPED LUTETIUM ORTHOPHOSPHATE (LOP) WAS SHOWN TO HAVE EXCEPTIONAL PROMISE AS A SCINTILLATOR MATERIAL BECAUSE OF A LIGHT OUTPUT TWICE THAT OF BISMUTH GERMANIUM OXIDE AND A DECAY TIME AN ORDER OF MAGNITUDE SHORTER. CERIUM-DOPED LOP CRYSTALS ARE CURRENTLY PRODUCED BY SLOWLY COOLING A MOLTEN SOLUTION WHICH HAS AN APPRECIABLE SOLUBILITY FOR THE SCINTILLATOR MATERIAL. CRYSTALS PRODUCED BY THIS METHOD ARE LARGE ENOUGH FOR DETERMINING FUNDAMENTAL PROPERTIES BUT TOO SMALL TO EFFICIENTLY FABRICATE DETECTOR CRYSTALS. A TOP-SEEDED SOLUTION GROWTH METHOD IS PLANNED IN PHASE I FOR PRODUCING CERIUM-DOPED LOP CRYSTALS COMMERCIALLY. THE FLUX USED TO GROW LOP CRYSTALS BY SLOW COOLING IS BASED ON LEAD PYROPHOSPHATE. WHILE THIS MATERIAL COULD BE USED TO GROW CRYSTALS BY THE TOP-SEEDED METHOD, CRUCIBLE CLEANING IS COMPLICATED BY THE NECESSITY TO DISSOLVE THE FLUX WITH STRONG ACIDS. FURTHERMORE, LEAD COMPOUNDS HAVE UNDESIRABLE TOXICOLOGICAL AND ENVIRONMENTAL PROPERTIES. USE OF POTASSIUM PYROPHOSPHATE IS PLANNED AS THE SOLVENT FOR GROWTH OF LOP BY THE TOP-SEEDED SOLUTION TECHNIQUE. THIS COMPOUND IS VERY SOLUBLE IN WATER AND HAS A REDUCED TOXICOLOGICAL AND ENVIRONMENTAL SENSITIVITY. DEVELOPMENT OF SOLUBILITY DATA FOR MOLTEN SOLUTIONS OF LOP AND POTASSIUM PYROPHOSPHATE SHOULD LEAD TO THE DEMONSTRATION OF FEASIBILITY FOR THE TOP-SEEDED SOLUTION GROWTH OF THIS NEW SCINTILLATOR CRYSTAL FROM A POTASSIUM PYROPHOSPHATE FLUX.