Pr3+‐doped LuPO4 emits UV radiation between 225 and 280 nm, where DNA shows strong absorption bands. Therefore, a systematic study of the luminescence of Pr3+ doped LuPO4 is performed: Different doping concentrations, particles sizes, and excitation schemes (vacuum UV at 160 nm and X‐rays 50 kV, 2 mA, tungsten target) are compared. The emission spectra in the UV range depends on the excitation energy and the particle size. Microcrystalline particles (6 µm) comprising 1% Pr3+ display the highest emission intensity at 234 nm upon vacuum UV as well as X‐ray excitation. Sub‐microscale particles (20–50 nm) of LuPO4:Pr3+ (1%) show the same UV emission under X‐ray excitation as the larger particles but do not emit under vacuum UV excitation. Colloidal nanoscale particles (5 nm) do not show emission in the UV‐C range. Based on the high‐density and strong X‐ray absorption of LuPO4, the implementation of Pr3+ doped LuPO4 particles of suitable size (20–50 nm) could improve the well‐established radiation therapy. Owing to the strong absorption and low penetration depth of UV‐C radiation in biological tissue, Pr3+‐doped LuPO4 particles located directly in cancerous tumors could allow for additional treatment with cell‐damaging UV‐C radiation.

The synthesis, crystal structure, photoluminescence (PL) and cathodoluminescence (CL) spectra of Ba 1−x Ca x Al 2 O 4 doped with 3 mol% Eu 2+ between x = 0 and x = 1 are described. The molar fractions of the alkaline earth elements were varied in steps of 0.1. The materials have been synthesized by all solid state reactions at 1300°C in mixed gas (H 2 /N 2). The identification of the crystal phases in the samples was based on analyses of the X-ray diffraction patterns. The Ba 1−x Ca x Al 2 O 4 system contains one dominant monoclinic phase, one dominant hexagonal phase and two different cubic phases that were present in low concentrations. The main characteristic of the PL spectra was that the intensity of the Eu 2+ photoluminescence decreased upon adding a second alkaline earth ion in the aluminate lattice. The hexagonal and monoclinic phases in the Ba 1−x Ca x Al 2 O 4 samples showed an unexpected behaviour, namely increasing their unit cell volumes upon decreasing the mole fraction of Ba 2+. For the hexagonal phase this behaviour has been explained qualitatively in terms of enhanced spontaneous polarization of the uncompensated anti-ferroelectric state.

3+.

Herein we describe the synthesis, crystal structures, photoluminescence (PL) and cathodoluminescence (CL) spectra of phosphors in the Sr0.97-xBaxEu0.03Al2O4 system between x = 0 and x = 0.97. The syntheses of these phosphors were carried out by solid state reactions at 1350°C in mixed gas (H2/N2). The molar fractions of the alkaline earth elements were varied in steps of 0.1. The Sr1-xBaxAl2O4 series manifested solid solutions of a monoclinic phase (at the Sr-rich side) and a hexagonal phase (at the Ba-rich side). At the Ba-rich side of Srx-1BaxAl2O4:Eu2+ we found evidence in the PL spectra that the hexagonal phase differed as the xBa fraction changed: it changed at room temperature from the ferroelectric P63 structure at xBa=1 to the paraelectric P6322 phase at xBa≈0.9 and at xBa≈0.8 it went back to P63. Unlike the PL spectra, the CL spectra of the hexagonal phase of Sr0.97-xBaxEu0.03Al2O4 at x ≥ 0.5 indicated only the paraelectric P6322 phase at room temperature.

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2+. -Sr 1-xSc2O4:xEu 2+ (x = 0-0.05) and SrSc2O4:Eu 2+ ,Dy 3+ are prepared by calcination of stoichiometric amounts of SrCO 3, Sc2O3, Eu2O3, and Dy2O3 (Mo boat, 1400 C, 12 h). Sr1-xSc2O4:xEu 2+ shows a broad emission with the maximum at 687 nm (deep red region) without any Eu-related emission. The highest photoluminescence (PL) intensity is obtained for x = 0.005 above which the intensity decreases again due to luminescence quenching. Temperature-dependent PL measurements reveal a T 1/2 value of 357 K. Additionally, persistent luminescence is observed in both SrSc2O4:Eu 2+ and SrSc 2O4:Eu 2+ ,Dy 3+ upon 525 nm excitation. -(MUELLER, M.; VOLHARD, M.-F.; JUESTEL*, T.; RSC Adv. 6 (2016) 10, 8483-8488, http://dx.