The sealed vertical Bridgman (VB) method is the main technique used to grow SrI2(Eu) crystals because SrI2(Eu) is very hygroscopic. In this study, we grew SrI2(Eu) single crystals with two-inch diameters and four-inch lengths using the VB method equipped with a removable chamber. The SrI2(Eu) single crystals were produced by the Liquinert process, which requires careful consideration of the crucible material and growth atmosphere. After a review of available materials, carbon crucibles were selected due to their several advantages over traditional quartz ampules: (1) they are suitable for large size crystal growth due to which they do not require any process for sealing of quartz ampule before the growth; (2) ease in controlling the temperature gradient because carbon crucibles can be heated directly via a high frequency induction heating system; and (3) carbon crucibles can assist in removing oxygen and moisture from the melt. The starting material, seed, and hot zone were prepared inside the glovebox in the removable growth chamber, which was used as the growth unit. This unit was installed in the growth system and heated to the melting point of SrI2(Eu) in a high-purity Ar atmosphere. The crucible in the growth chamber was then displaced in the downward direction for crystal growth. Crack-free SrI2(Eu) bulk single crystals with two-inch diameters were produced. The crystals were cut into cylindrical specimens (diameter = length = 2 in.), polished, and sealed in an aluminum case with a quartz glass window for evaluation. Negligible self-absorption was observed because of the large length of the crystal. The light output of the SrI2(Eu) examined in this study was estimated to be 70 000 photons/MeV, and the calculated energy resolution was 3.4% (662 keV, full width at half-maximum) at room temperature.
ASJC Scopus subject areas
- 化学 (全般)