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Abstract In this review, modern insights into the synthesis and fundamental optical properties as well as applications of divalent lanthanides as spectral energy converters are discussed, which have especially evolved within the last two decades. An emphasis is put on the state-of-the-art knowledge about the luminescence of other divalent lanthanides than the most commonly applied representative Eu2+ and what special features in their luminescence arises due to the different number of 4f n electrons. In particular, the luminescence of Sm2+, Tm2+, Yb2+ and the less stable ions Nd2+ and Dy2+ will be regarded. A broad overview over the synthetic approaches to inorganic compounds based on divalent lanthanide ions will be conveyed as well and shall demonstrate the fascinating developments in the field of inorganic solid-state chemistry of the lanthanides. Besides their fundamental optical properties, also applications of the presented divalent lanthanide activators are discussed. Sm2+ is a well-known temperature and pressure sensor due to its interconvertible 4f‐4f and 5d-4f transitions. Moreover, nanocrystalline BaFCl:Sm2+ has an appreciable potential as novel X-ray storage phosphor. Tm2+ is interesting for upconversion in photovoltaic and lasing applications, whereas Yb2+ in halides may be a promising alternative to Eu2+ for scintillation materials and phosphors for light-emitting diodes (LEDs). Nd2+ and Dy2+ are currently emerging as novel near infrared (NIR)-absorbing and emitting activators that might become interesting as lasing ions. The spectroscopy of these unusual lanthanide ions provides many non-trivial features due to the excited two-open shell 4fn-15d1 configuration overlapping with the excited 4f n levels. Finally, a perspective for future developments will be given. [ABSTRACT FROM AUTHOR]

The Tm-doped MgAl 2 O 4 single crystals were synthesized by using Xe arc lamps-equipped floating zone furnace. The synthesized crystals exhibited luminescence due to the 4f-4f transitions of Tm3+ in photoluminescence (PL), scintillation, and thermally stimulated luminescence (TSL). In all of PL, scintillation, and TSL, the 0.5% Tm-doped crystal showed the highest luminescence intensity. In TSL dose response functions, the 0.5% Tm-doped crystal showed sensitivity from X-ray irradiation with 0.1 mGy. In addition, we measured linear energy transfer (LET) dependence on TSL glow curve of the crystal and X-ray imaging test taken by TSL. We revealed the spatial resolution of the crystal was 100 μm. • We have characterized the photoluminescence, scintillation, and dosimetric properties of Tm-doped MgAl 2 O 4 single crystals. • All the crystals showed luminescence properties due to Tm3+ ion. • We revealed possibility of Tm-doped MgAl 2 O 4 crystal for personal dosimetry, 2D dosimetry, and heavy ion beam measurement. [ABSTRACT FROM AUTHOR]

Hafnium-based materials are attractive for a scintillator owing to their high density and effective atomic number. In this study, single crystals of Ce-doped calcium hafnate perovskite (Ce:CaHfO 3) were synthesized from a Ca-rich composition, and photoluminescence (PL) and scintillation properties were investigated. The X-ray diffraction patterns revealed that the synthesized single crystals were a single phase of CaHfO 3. The Ce:CaHfO 3 exhibited blue luminescence at 430 nm and fast decay due to the 5d–4f transition of Ce3+ in both PL and scintillation. From the measurement of pulse height spectra under 137Cs irradiation, the highest light yield of 7800 photons/MeV was observed in the 3% Ce:CaHfO 3. • Single crystals of Ce-doped calcium hafnate perovskite (Ce:CaHfO 3) were successfully synthesized from a Ca-rich composition. • Ce:CaHfO 3 exhibited blue luminescence and fast decay due to the 5d–4f transition of Ce3+ in both PL and scintillation. • The light yield of 7800 photons/MeV was observed in the 3% Ce:CaHfO 3 under 137Cs gamma-ray irradiation. [ABSTRACT FROM AUTHOR]

Single crystals of Ce-doped Cs 3 LaCl 6 and Cs 3 LaBr 6 show promising scintillation properties in gamma-ray detection. Their thermal response in the range from 40 K to 500 K is discussed in this work. The steady state photoluminescence spectra, photoluminescence decay time, and X-ray excited radioluminescence of Ce-doped and undoped Cs 3 LaCl 6 and Cs 3 LaBr 6 were studied. The photoluminescence and radioluminescence emission intensity of the Ce-doped crystals decreases less than 25% from 40 K to 500 K. The photoluminescence decay time of Ce 3+ increases with increasing temperature. [ABSTRACT FROM AUTHOR]