关键词: 稀土卤化物, K₂LaBr₅∶Pr, 坩埚下降法, 光致发光, 衰减时间

Abstract: K₂LaBr₅ polycrystalline materials with different doping concentrations of Pr³⁺ were synthesized by high-temperature solid-state method, and the K₂LaBr₅∶Pr single crystals were grown by vertical Bridgman technique, and cylindrical transparent crystals with ø12 mm×5 mm were obtained by a series of processing. The crystal belongs to the orthogonality system and the cell parameters has been determined as a=1.336 0 nm, b=0.992 7 nm, c=0.846 2 nm, Z=4, the crystal density is 3.908 g/cm³, the melting point is 607 ℃. The crystals were characterized by powder X-ray diffraction, X-ray excitation emission spectrum, photoluminescence spectrum, transmittance and so on. Under the excitation of ultraviolet light and X-ray, the K₂LaBr₅∶Pr crystal exhibits blue light (³P₁→³H₄), green light (³P₀→³H₄,³P₁→³H₅), orange light (³P₁→³H₆,³P₁→³F₂), red light (³P₀→³F₂,³P₁→³F₃), deep red light (³P₁→³F₄), purple light (³P₀→³F₄) and other visible wavelengths of light output in the wavelength range of 480 nm to 750 nm, which indicates that the crystal has excellent luminescent properties. Under X-ray excitation, a broadband 4f 5d-4f² emission transition is also observed in the range of 360 nm to 440 nm. The scintillation decay time of K₂LaBr₅∶Pr crystal is about 10 μs, which is measured by the steady-state transient fluorescence spectrophotometer, and the transmittance of the crystal in the visible range is 88% measured by the ultraviolet-visible spectrophotometer.

Key words: rare earth halide, K₂LaBr₅∶Pr, Bridgman technique, photoluminescence, decay time