Optical and Scintillation Properties of Hf⁴⁺ Codoped SrI₂:Eu²⁺ Single Crystals

Single crystals of Eu
²⁺
-activated SrI
₂
, one of the most leading-edge scintillators for gamma-ray spectroscopy applications, have a low radioactive background, excellent energy resolution of 2.6%–3% at 662 keV, and high light yield of 80 000–120 000 photons/MeV. In this article, tetravalent ions codoping, namely, Hf
⁴⁺
codoping, was used to enhance its scintillation performance.
$\emptyset 12$
mm diameter SrI
₂
:Eu
²⁺
single crystals codoped with 0, 0.05, 0.1, and 0.2 at% Hf
⁴⁺
were successfully grown by the multiampoule Bridgman method. All grown crystals are highly transparent, crack-free, and inclusion-free. The effects of Hf
⁴⁺
codoping concentration on the optical and scintillation properties were studied. The gamma-ray energy resolutions of SrI
₂
:Eu single crystals can be improved from 3.4% to 3.1% at 662 keV, and from 6.6% to 6.0% at 122 keV upon 0.05 at% Hf
⁴⁺
codoping.