Systematic Search for New Lanthanum Scintillators

The objective of this work is the discovery of new lanthanum scintillators for ambient-temperature gamma-ray spectroscopy. Increasing the number of known scintillator materials increases the potential for producing crystals with good energy resolution in larger sizes and at lower cost than those currently available. Through solid-state reactions we have synthesized 20 microcrystalline lanthanum samples in undoped form and doped with 1% Ce³⁺. We used X-ray diffraction to verify the crystal phase, pulsed X-ray excitation to measure the luminosity and decay time of the scintillation light, and optical excitation to measure the emission wavelength. In undoped form, many materials exhibit slow charge transfer emission within polyatomic anionic groups and, in one case, fast core-valence emission. In doped form, the lanthanum oxyhalides (LaOCl, LaOBr and LaOI) and one lanthanum phosphate (CsLa(PO₃)₄) showed bright and fast emission characteristic of cerium activation.