The Influence of Light Anion Impurities Upon SrI2(Eu) Scintillator Crystals

To better identify the influence of light anion impurities on the scintillation performance, small boules of SrI
₂
(Eu) were grown by the vertical Bridgman-Stockbarger method, each co-doped with 0.2% of one of the following: C
⁰
, CO3
^2-
, N
^3-
, O
^2-
, OH
^-
, PO4
^3-
, S
^2-
, SO4
^2-
, Cl
^-
and Br
^-
. Residual impurity concentrations were measured, and the scintillation performance of resulting detectors was characterized. Oxygen was tolerated up to 0.2% on a molar basis. Sulfur proved to be highly detrimental to both crystallinity and scintillation performance. Nitrogen produced additional emission near 480 nm. This study suggests that SrI
₂
(Eu) readily incorporates anion impurities, which may substitute for iodine, but these may also be removed before and during growth by volatilization. Purity metrics for starting materials should include sulfur and carbon, as well as oxygen and H
₂
O.