Crystal growth and scintillation properties of Tm:K2NaLuF6

Chemically stable and transparent K2NaLuF6 single crystals doped with Tm3+ ions were grown by the micro-pulling down method (μ-PD). X-ray diffraction measurements showed that the as-grown crystals possess cubic structure with Fm3m space group. The radio- and photo-luminescence spectra of the grown crystals were measured in the vacuum ultraviolet (VUV) and ultraviolet (UV) regions. Tm:K2NaLuF6 showed high emission intensity at 188 nm in the radio- and photo-luminescence spectra (λexc = 159 nm). The decay time and light yield of Tm:K2NaLuF6 were also investigated by 241Am 5.5 MeV α-ray irradiation. The main component of the decay time was a 4-8 μs and this emission was considered as 5d-4f emission from 4fn − 15d high-spin state (parity allowed and spin forbidden transition). In addition to this, the light yield of Tm-doped K2NaLuF6 single crystals systematically increased with increasing Tm concentration.