A scintillator composition is disclosed, containing a solid solution of at least two cerium halides. A radiation detector for detecting high-energy radiation is also described herein. The detector includes the scintillator composition mentioned above, along with a photodetector optically coupled to the scintillator. A method for detecting high-energy radiation with a scintillation detector is also described, wherein the scintillation crystal is based on a mixture of cerium halides.