Synthesis and luminescence of Cs2HfCl6 micro- and Cs2HfF6 nanoparticles

Abstract

Hafnium-based halide crystals are attractive wide-bandgap phosphor materials for scintillation applications due to their high density, low hygroscopicity and bright radioluminescence. Here, we describe synthetic approaches towards the formation of Cs₂HfCl₆ (CHC) microparticles and Cs₂HfF₆ (CHF) nanocrystals. The structure of the obtained materials was characterised by means of powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface chemistry was studied by attenuated total reflection infrared spectroscopy (ATR-IR) and dynamic light scattering (DLS) while thermal properties were determined with thermogravimetric analysis (TGA). The optical properties of the products were elucidated through absorption (UV-vis) and photoluminescence (PL/PLE) spectra. Intrinsically luminescent CHC can be synthesised as a micropowder through an emulsion synthesis. The synthesis of pure and Eu- or Mn-doped CHF nanopowders in organic solvents at 160 °C and atmospheric pressure is also disclosed. These materials might pave the way towards the versatile additive manufacturing of lead-free and dopant-free, particle-based scintillator materials.