Abnormal Eu 3+ → Eu 2+ Reduction in Ca 9− x Mn x Eu(PO 4) 7 Phosphors: Structure and Luminescent Properties.

Autor: Sipina, Elena V., Spassky, Dmitry A., Krutyak, Nataliya R., Morozov, Vladimir A., Zhukovskaya, Evgenia S., Belik, Alexei A., Manylov, Mikhail S., Lazoryak, Bogdan I., Deyneko, Dina V.
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Zdroj: Materials (1996-1944); Feb2023, Vol. 16 Issue 4, p1383, 22p
Abstrakt: β-Ca3(PO4)2-type phosphors Ca9−xMnxEu(PO4)7 have been synthesized by high-temperature solid-phase reactions. The crystal structure of Ca8MnEu(PO4)7 was characterized by synchrotron X-ray diffraction. The phase transitions, magnetic and photoluminescence (PL) properties were studied. The abnormal reduction Eu3+ → Eu2+ in air was observed in Ca9−xMnxEu(PO4)7 according to PL spectra study and confirmed by X-ray photoelectron spectroscopy (XPS). Eu3+ shows partial reduction and coexistence of Eu2+/3+ states. It reflects in combination of a broad band from the Eu2+ 4f65d1 → 4f7 transition and a series of sharp lines attributed to 5D0 → 7FJ transitions of Eu3+. Eu2+/Eu3+ ions are redistributed among two crystal sites, M1 and M3, while Mn2+ fully occupies octahedral site M5 in Ca8MnEu(PO4)7. The main emission band was attributed to the 5D0 → 7F2 electric dipole transition of Eu3+ at 395 nm excitation. The abnormal quenching of Eu3+ emission was observed in Ca9−xMnxEu(PO4)7 phosphors with doping of the host by Mn2+ ions. The phenomena of abnormal reduction and quenching were discussed in detail. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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