Crystal growth of large diameter strontium iodide scintillators using in Situ stoichiometry monitoring

The scintillation radiation detection community is on the cusp of a major breakthrough with the potential deployment of Europium-activated Strontium Iodide (SrI2:Eu) detectors for medical imaging and homeland security applications. Compared to the traditional scintillators (such as NaI), SrI2 provides much better energy resolution and light output. The crystal growth of SrI2:Eu has been impaired for a long time due to cracking problems, which makes it highly unreliable and nonreproducible. This significantly increases the cost of the material which in turn impedes wide-scale deployment and limits its advantages over other scintillators. In this paper, we demonstrate a technique of growing crack-free SrI2:Eu crystals by monitoring the stoichiometry of the melt atmosphere during processing and crystal growth. Using the feedback information from the in situ monitoring technique, the stoichiometry of the melt was corrected and multiple crack-free SrI2:Eu crystals of diameters 1.5 inches were repeatedly grown using Bridgman configuration with no visible inclusions, bubbles or defects whatsoever.