Efficient Generation of Stable Sm²⁺ in Nanocrystalline BaLiF₃:Sm³⁺ by UV- and X-Irradiation

Abstract

In recent decades, storage phosphors have found widespread applications in the fields of dosimetry and computed radiography due to their impressive properties, including large dynamic ranges and passive storage modalities. Despite this success, further development of highly efficient X-ray- and UV-sensitive luminescent materials is still desirable, in particular for applications in dosimetry. In this article, we report X-ray and UV storage properties of nanocrystalline barium lithium fluoride (BaLiF3) doped with Sm3+. Nanocrystalline BaLiF3:Sm3+ was prepared mechanochemically by ball milling and the resulting product was characterized by powder X-ray diffraction and transmission electron microscopy. The response of the phosphor to X-ray and UV radiation was investigated by measuring room temperature photoluminescence spectra before and after irradiation for a wide range of doses. The lifetime of the Sm2+ emission at 694 nm was determined for both the X-ray and UV irradiated powder samples. The results indicate a potential for Sm3+-activated nanocrystalline BaLiF3 to be used in dosimetry applications.

Yb3+ and Er3+ Codoped BaLiF3 Nanocrystals for X-ray Dosimetry and Imaging by Upconversion Luminescence

“…It is noted here that a similar X-ray dependence of the upconversion luminescence was observed in nanocrystalline SrFCl:Er 3+ , Yb 3+ with reduction rates of 0.08 and 0.01 Gy –1 for the UCL intensity . It appears that in both systems, a certain percentage of Er and Yb ions cannot be reduced by X-irradiation as their trivalent oxidation state may be highly stabilized by next nearest neighbor defects such as oxide ions (O 2– ) in the halide host lattice …”

“…Compared to many other fluoride-based systems, BaLiF 3 is nonhygroscopic, and optically active rare-earth ions can be readily doped into this inverse perovskite host lattice by high-temperature synthesis and mechanochemical methods. Nonactivated BaLiF 3 has also emerged as a promising optical window material due to its wide band gap of 6.8 eV. , As a host material, this system has potential applications in the fields of dosimetry, computed radiography, and quantum cutting, , when activated with rare-earth ions. BaLiF 3 can be readily prepared from equimolar amounts of BaF 2 and LiF by mechanochemical methods including high-energy ball milling. , Recently, BaLiF 3 has been investigated as a potential upconversion host material.…”

Photoluminescence of X-ray-Induced Divalent Tm Ions in BaLiF3:Tm3+ Nanocrystals

“…(a) Photoluminescence spectra of X-ray-induced Eu 2+ in BaLiF 3 :Eu 3+ (blue trace), Sm 2+ in BaLiF 3 :Sm 3+ (red trace, ref ), and Tm 2+ in BaLiF 3 :Tm 3+ (green trace). (b) Dependence of the integrated luminescence of Eu 2+ (4f 6 5d → 8 S 7/2 (4f 7 )) at 422 nm (blue markers), Sm 2+ ( 5 D 0 → 7 F 1 ) at 694 nm (red markers, ref ), and Tm 2+ ( 2 F 5/2 → 2 F 7/2 ) at 1136 nm (green markers), as a function of the X-ray dose. Solid lines represent double exponential fits.…”

“…We have recently reported some photoluminescence properties of Sm 3+ -doped BaLiF 3 prepared by Ball milling and demonstrated its potential as an X-ray and UV storage phosphor . In the BaLiF 3 :Sm 3+ phosphor, the Sm 3+ ions (located at the centrosymmetric Ba 2+ sites) are reduced to stable Sm 2+ by radiation-generated electrons.…”

“…We have recently reported some photoluminescence properties of Sm 3+ -doped BaLiF 3 prepared by Ball milling and demonstrated its potential as an X-ray and UV storage phosphor. 19 In the BaLiF 3 :Sm 3+ phosphor, the Sm 3+ ions (located at the centrosymmetric Ba 2+ sites) are reduced to stable Sm 2+ by radiation-generated electrons. The Sm 2+ luminescence can be efficiently photoexcited by the broad 4f 6 −4f 5 5d absorption band around 470 nm and read out by the relatively narrow and sharp magnetic dipole-allowed 5 D 0 → 7 F 1 Sm 2+ luminescence at 694 nm.…”