title: Using Eu(3+) as an atomic probe to investigate the local environment in LaPO4-GdPO4 monazite end-members.
abstract: In the present study, we have investigated the luminescent properties of Eu(3+) as a dopant in a series of synthetic lanthanide phosphates from the monazite group. Systematic trends in the spectroscopic properties of Eu(3+) depending on the size of the host cation and the dopant to ligand distance have been observed. Our results show that the increasing match between host and dopant radii when going from Eu(3+)-doped LaPO4 toward the smaller GdPO4 monazite decreases both the full width at half maximum of the Eu(3+) excitation peak, as well as the (7)F2/(7)F1 emission band intensity ratio. The decreasing Ln⋯O bond distance within the LnPO4 series causes a systematic bathochromic shift of the Eu(3+) excitation peak, showing a linear dependence of both the host cation size and the Ln⋯O distance. The linear relationship can be used to predict the energy band gap for Eu(3+)-doped monazites for which no Eu(3+) luminescent data is available. Finally, mechanisms for metal-metal energy transfer between host and dopant lanthanides have been explored based on recorded luminescence lifetime data. Luminescence lifetime data for Eu(3+) incorporated in the various monazite hosts clearly indicated that the energy band gap between the guest ion emission transition and the host ion absorption transition can be correlated to the degree of quenching observed in these materials with otherwise identical geometries and chemistries.
authors.affiliation: Helmholtz-Zentrum Dresden - Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden, Germany. Electronic address: n.huittinen@hzdr.de.
authors.forename: Nina
authors.initials: N
authors.lastname: Huittinen
authors.affiliation: Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6), 52425 Jülich, Germany. Electronic address: y.arinicheva@fz-juelich.de.
authors.forename: Yulia
authors.initials: Y
authors.lastname: Arinicheva
authors.affiliation: Helmholtz-Zentrum Dresden - Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden, Germany. Electronic address: moritz.schmidt@hzdr.de.
authors.forename: Moritz
authors.initials: M
authors.lastname: Schmidt
authors.affiliation: Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Nuclear Waste Management and Reactor Safety (IEK-6), 52425 Jülich, Germany. Electronic address: s.neumeier@fz-juelich.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Neumeier
authors.affiliation: Helmholtz-Zentrum Dresden - Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, 01328 Dresden, Germany. Electronic address: t.stumpf@hzdr.de.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Stumpf
keywords: Eu(3+); Incorporation; Luminescence; Monazite; Quenching; TRLFS