Determination of the Crystallographic Orientation of SrI_2 Crystals

Abstract

Single crystals of strontium iodide (SrI2), an important material for nuclear detector applications, are grown commercially in cylindrical ampoules using the Bridgman self-seeding method. As a result, the axial orientation of Bridgman boules varies from run to run. Most crystal growth methods benefit from the use of oriented seeds, which can be helpful in maximizing growth rates and crystal quality. However, it is very difficult to orient SrI_2 crystals because they are deliquescent and their surfaces damage easily during cutting and polishing. In this study, unpolished facets formed on an edge-defined film-fed growth (EFG) boule were used to generate the first Laue patterns. The principal boule used in this study had a square cross section and was grown using a seed cut from along the growth axis of a Bridgman boule. X-ray analysis showed that the EFG boule grown from this seed grew along the b-axis and the side facets were the (100) and (001) faces. This work made possible the fabrication of oriented SrI2 seeds for use in future EFG and Czochralski growth experiments and allowed for the determination of the optic axes using polarized light.