Growth and Luminescent Properties of Cs2HfCl6 Scintillators Doped With Alkaline Earth Metals

Nondoped Cs ₂ HfCl ₆ (CHC) and alkaline earth metal-doped CHC (AE:CHC) crystals were grown by the vertical Bridgman-Stockbarger method. The spectra of the AE:CHC under X-ray excitation were similar to those for the AE-free crystal; thus, AE doping did not change emission wavelength of CHC. We determined the light outputs and energy resolutions of nondoped CHC and AE:CHC by measuring pulse-height spectra under 662-keV gamma-ray excitation of a ¹³⁷ Cs source. Both light output and energy resolution were deteriorated with AE doping. For example, nondoped CHC had a light output of _~ 44 000 photons/MeV and energy resolution of ~5.2%; on the other hand, Sr 0.5 at.%-doped CHC had a light output of only _~ 28 000 photons/MeV and energy resolution of _~ 10%. Scintillation decay also did not change. The nonproportional response values of light output versus gamma-ray energy did not improve in AE:CHC either. Therefore, doped AEs can be responsible for creation of defect trap levels which would hamper the carrier transport in CHC structure.