Growth, structure, and temperature dependent emission processes in emerging metal hexachloride scintillators Cs₂HfCl₆...

Area of Science:

• Materials Science
• Nuclear Instrumentation
• Solid State Physics

Background:

• Metal hexachloride crystals, specifically Cs₂HfCl₆ and Cs₂ZrCl₆, are emerging as promising scintillators.
• Their excellent energy resolution makes them attractive for scintillation applications.

Purpose of the Study:

• To investigate the crystal structure and scintillation properties of Cs₂HfCl₆ and Cs₂ZrCl₆.
• To examine these properties over a broad temperature range (9–300 K).

Main Methods:

• X-ray diffraction was used to confirm crystal structure.
• Scintillation light yield and energy resolution were measured using a ¹³⁷Cs gamma source.
• Alpha-to-beta ratios were determined using an ²⁴¹Am alpha source.
• Scintillation decay curves were analyzed to understand recombination processes.

Main Results:

• Both Cs₂HfCl₆ and Cs₂ZrCl₆ exhibit a cubic structure (space group Fm3m) across the studied temperature range.
• Room temperature light yields are 24,800 photons/MeV for Cs₂HfCl₆ and 33,900 photons/MeV for Cs₂ZrCl₆, with energy resolutions of 5.3% and 4.5%, respectively.
• Alpha-to-beta ratios are 0.39 for Cs₂HfCl₆ and 0.35 for Cs₂ZrCl₆.
• A notable enhancement in scintillation yield was observed between 125–150 K due to negative thermal quenching.

Conclusions:

• Cs₂HfCl₆ and Cs₂ZrCl₆ possess favorable scintillation characteristics for detector applications.
• The observed negative thermal quenching is attributed to the thermal activation of trapped carriers.
• A model for the emission center was proposed to explain temperature-dependent emission intensity changes.