Light yield and thermal quenching of Ce³⁺ and Pr³⁺ co-doped LaBr₃:Sm²⁺ near-infrared scintillators

LaBr₃:Ce³⁺ is a compound with excellent scintillation properties, but its ultraviolet emission does not match well with the detection efficiency curves of silicon based photodetectors. In this work, Sm²⁺ is studied as an activator for LaBr₃ as its near-infrared emission can be detected with close to 100% efficiency by such photodetectors. LaBr₃:Sm²⁺ single crystals were grown with and without co-doping of Ce³⁺ or Pr³⁺. The samples were studied by means of X-ray excited and photoluminescence spectroscopy at temperatures between 10 K and 300 K. Their spectroscopic properties are compared to LaBr₃:Ce³⁺ and LaBr₃:Eu²⁺. The effect of using Ce³⁺ or Pr³⁺ as scintillation sensitiser for Sm²⁺ is assessed. It is found that energy transfer from host to Sm²⁺ greatly improves upon Ce³⁺ co-doping, but the quenching temperature of the Sm²⁺ emission decreases. The quenching mechanism of both the Ce³⁺ and Sm²⁺ emission in LaBr₃ is elaborated on. Furthermore, the effect of charge compensating defects on the light yield and spectroscopic properties is discussed.