A scintillator composition is described, including a matrix material and an activator. The matrix material includes at least one lanthanide halide compound. The matrix can also include at least one alkali metal, and in some embodiments, at least one alkaline earth metal. The composition also includes a praseodymium activator for the matrix. Radiation detectors that include the scintillators are disclosed. A method for detecting high-energy radiation with a radiation detector is also described.