Photoluminescence, photoacoustic, and scintillation properties of Te⁴⁺-doped Cs₂HfCl₆ crystals

Photoluminescence, photoacoustic, and scintillation properties are reported for 1.0, 3.0, 5.0, and 10 mol% Te⁴⁺-doped Cs₂HfCl₆ crystals grown using the vertical Bridgman–Stockbarger method. The UV − VIS light excited emission spectra showed an emission band peaking at 575 nm which can be ascribed to transitions from the ³T_1u and ³A_1u states to the ¹A_1g state of Te⁴⁺ ions. Excitation spectra monitored at emission wavelength of 575 nm showed bands at 230–250 (charge transfer on a HfCl₆ ²⁻), 275–300 (¹A_{1 g} → ³T_{1 u}), 300–340 (¹A_{1 g} → ³T_{2 u}, ³E_u), and 360–460 nm (¹A_{1 g} → ¹T_{1 u}). The X-ray induced scintillation spectra exhibited a yellow emission band at 575 nm, which is similar to the emission band for excitation by UV–VIS light. Scintillation light yields of the crystals were estimated to be approximately 11,700 (1.0 mol%), 13,100 (3.0 mol%), 9600 (5.0 mol%), and 9000 (10 mol%) photons/MeV, respectively. Scintillation light yield was inversely correlated with the PA intensity.