Cathodoluminescence and Photoluminescence of YPO₄:Pr³⁺, Y₂SiO₅:Pr³⁺, YBO₃:Pr³⁺, and YPO₄:Bi³⁺

Abstract

Herein we describe the synthesis, characterization, and cathodoluminescence of the UV emitting phosphors YPO 4 :Pr 3+ , Y 2 SiO 5 :Pr 3+ , YBO 3 :Pr 3+ , and YPO 4 :Bi 3+ . These photoluminescent UV phosphors exhibited strong luminescence in the UV part of the electromagnetic spectrum when excited by electron bombardment. Spectra have been recorded between 210 and 650 nm at electron beam energies of 5, 10 and 15 keV. The energy efficiencies of YPO 4 :Pr 3+ , Y 2 SiO 5 :Pr 3+ , YBO 3 :Pr 3+ and YPO 4 :Bi 3+ in the UV range were 9.2%, 2.7%, 5.1%, and 7.2%, respectively at 15 keV. UV photoluminescence measurements were conducted using 160 nm excitation generated by combining a VUV monochromator with a deuterium lamp. The UV emitting phosphor Y 2 SiO 5 :Pr 3+ has attracted attention both because of its potential application as a UV tunable laser and also as a scintillator arising from its short decay time (of about 40 ns).1-4 Moreover, it is one of the first UV emitting materials, which manifests up-conversion of blue radiation into the UV-C range. 5Interest rose in UV-A and UV-B emitting luminescent materials after the introduction of low-pressure Hg discharge lamps that were developed as sun tan lamps in the middle of the 20 th century. 6 The early UV emitting phosphors were activated by Tl + , Pb 2+ , or Bi 3+ , while later Ce 3+ activated phosphors such as LaPO 4 :Ce and YPO 4 :Ce came into play due to their better stability and environmental compliance as they contained no hazardous elements.The development of phosphors emitting in the UV-C range was stimulated by the advent of efficient dielectric barrier Xe discharge lamps some decades ago. [7][8][9] At that time, some UV- have since become less interesting due to the toxic character of these materials. One of the most efficient UV-C emitting materials, which also has a rather high thermal quenching temperature, is YPO 4 :Bi .10 However a serious drawback with this material is the limited stability of Bi 3+ cations toward oxidation or reduction. This necessitated a search for efficient and long-term stable Pr 3+ activated materials, since it is thought that Pr 3+ can withstand the harsh conditions of VUV radiation and the electron bombardment inside an excimer discharge tube. The most efficient materials amongst the many, which have been published so far are YPO 4 :Pr, LaPO 4 :Pr, Y 2 SiO 5 :Pr, YBO 3 :Pr, Ca 9 Y(PO 4 ) 7 :Pr, LuBO 3 :Pr, Lu 2 SiO 5 :Pr and LuPO 4 :Pr. The later Lutetium containing compounds are also regarded as scintillators because of their high density.Xe excimer discharge lamps containing a UV-C phosphor for germicidal action and photochemical purposes have been developed by several groups 11-13 and lamp products containing YPO 4 :Nd, YPO 4 :Pr, YPO 4 :Bi, and LaPO 4 :Pr were introduced several years ago. Even though these lamps can achieve wall plug efficiency close to that of low-and medium-pressure Hg discharge lamps, their commercial success is rather moderate so far. The main reason for this observation is their lower long-term stabi...

Deep Ultraviolet Emitting Scintillators for Biomedical Applications: The Hard Way of Downsizing LuPO4:Pr3+

“…Furthermore, two narrow emission bands can be observed at 488 nm (2.54 eV) and 492 nm (2.52 eV). These two very narrow emission peaks are in line with data from literature and are attributed to the 3 P 0 → 3 H 4 transition which originates from the lowest 4f5d crystal field component …”

“…Samples with a higher Pr 3+ concentration display one narrow and intense peak at 618 nm. This effect was observed in a previous work by Broxtermann et al They attributed this band to the 3 P 0 → 3 H 6 transition …”

“…As the concentration increases, the luminescence is quenched . The two peaks at 614 and 618 nm are attributed to the 3 P 0 → 3 H 6 transition, reaching their highest intensity at 3% Pr 3+ …”

“…The X‐ray tube was equipped with a tungsten target and was placed perpendicular to the specimen. All samples were normalized to a YPO 4 :Bi 3+ standard from Philips, one of the most efficient UV‐C‐emitting materials …”

Characterization of Micro‐ and Nanoscale LuPO4:Pr3+,Nd3+ with Strong UV‐C Emission to Reduce X‐Ray Doses in Radiation Therapy

“…When the nanoscale crystals were excited by X‐rays, the emission spectra of all samples showed the same four characteristic peaks of Pr 3+ ‐doped LuPO 4 as observed for the microscale particles as depicted in Figure a. For a better comparison with previous literature, the emission spectra of the samples were normalized to the emission maximum of YPO 4 :Bi 3+ from Philips . The resulting integrals are presented in Figure b.…”