1D all-inorganic metal halide Rb2AgX3 (X = Cl, Br): Pb-free scintillator materials for ionising radiation detection

Abstract

Rb-based metal halide materials possess large attenuation coefficients and bright luminescence making them suitable as scintillators for X-ray detection. Here, we present the first report of an optimised anti-solvent synthesis method enabling gram-scale preparation of phase-pure Rb₂AgX₃, (X = Cl, Br) metal halides, which show broadband emission centred at 585 nm and 514 nm, respectively. We have identified solvent selection criteria that are broadly applicable to the synthesis of a wider variety of perovskite materials. This approach offers several advantages: reduced reaction temperatures, shorter reaction times, enhanced purity, and increased yields. Collectively, these improvements contribute to a more sustainable and scalable synthesis route. Rb₂AgX₃, (X = Cl, Br) metal halides report fast radiative recombination with typical decay times of sub-10 ns. Optical and radioluminescence measurements revealed halide-specific emission pathways with Rb₂AgCl₃ displaying superior emission intensities, whereas Rb₂AgBr₃ consistently elicited a stronger X-ray induced response. High pressure XRD studies measured bulk crystal moduli indicating that the Rb₂AgCl₃ crystal structure has a stiffer lattice than the Rb₂AgBr₃ analogue. Compressing pellets of polycrystalline Rb₂AgX₃ over a range of pressures (both at room temperature and 70 °C) confirmed this lattice stiffness trend and allowed for improvements in material densification and optical clarity at thicknesses of >250 µm. The X-ray response of these pellets improved with increasing pressure for the bromide analogue underscoring the importance of microstructural control in enhancing scintillation efficiencies.