Luminescence and X‐ray phosphor properties of samarium and lanthanum‐doped cubic barium chloride

Abstract

Lanthanum and samarium‐doped barium chloride samples with composition of the form Ba1‐x‐yLaxSmyCl2+x+y with x = 0.125 and 0 < y < 0.01 have been prepared in transparent ceramic form. X‐ray diffraction confirms that the material adopts the high temperature cubic (fluorite) phase of barium chloride. The photoluminescence spectrum shows a combination of broad band 5d and narrow 4f transitions. The broad band can be decomposed into strong and weak components which we attribute to Sm2+ ions with and without an adjacent interstitial Cl‐ ion respectively. The temperature dependence of the strongest broad band indicates that the lowest 5d level is 800 cm‐1 above the 5D0 level. The X‐ray induced fluorescence spectrum shows an additional blue emission band for Sm concentrations y < 0.01 centred at around 420 nm which is ascribed to excitonic processes involving H centres. This emission band coincides with a photoluminescence excitation band for Sm2+ in this material, and so it is likely that the X‐ray induced luminescence from Sm2+ arises via an energy transfer process. Scintillation arising from the blue band can be observed, but is characterised by a long tail extending over hundreds of microseconds. The relative efficiency of the material as an X‐ray phosphor compared to commercial terbium‐doped gadolinium oxysulphide is around 11%. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth and characterization of neodymium and ytterbium doped barium chloride dihydrate single crystals

“…1(c) may be due to the formation of halide centres called H-centres [13]. The rare earth ions will substitute for barium ions and more additional chlorine ions from the RECl 3 (RE=Nd,Yb) may occupy the interstitial sites of the lattice.…”

Sm2+ fluorescence and absorption in cubic BaCl2: Strong thermal crossover of fluorescence between 4f6 and 4f55d1 configurations

“…The lifetimes of the 4f 5 5d 1 states show a complex behaviour with different relaxation rates ranging over many orders of magnitude, and it appears that our preliminary estimates [15] did not account for long decay time relaxation, probably because the repetition rate used in the excitation process was too fast. Revised measurements will be reported elsewhere together with a detailed account of the scintillation and X-ray phosphor performance of LSCBC, but for the present purpose it suffices to state that the 4f 6 ( 5 D 0 ) state shows a simple exponential decay with a lifetime of 13 ms at 12 K, and we use that value here as an estimate of the radiative lifetime.…”

“…In a preliminary report [15], we have shown that LSCBC:Sm 2 þ has a red-emission scintillation efficiency of around 5% of the commercial X-ray phosphor terbium-doped gadolinium oxysulphide. The prime motivation for the present work is to understand the spectroscopy of the LSCBC:Sm system in order to optimise the X-ray phosphor performance.…”

Luminescence and spectroscopic properties of Sm2+ and Er3+ doped SrI2

“…Also the Sm 2 þ 5d-4f emission is dipole and spin-allowed, but experimental data on its decay time are scarce. The reported values range from 400 ns to 3 ms [8][9][10]. In compounds where the Sm 2 þ 4f 6 [ 5 D 0 ] level is below the lowest Sm 2 þ 4f 5 5d level, narrow Sm 2 þ 4f-4f emission bands with millisecond decay time are usually observed, see e.g.…”