Abstract
AbstractA series of commercial and prepared CaS:Eu2+ rare earth activated phosphors are investigated following different post‐synthetic treatments. A number of species directly related to the function of the material are characterized using electron paramagnetic resonance (EPR) spectroscopy. Isolated Eu2+ sites are identified and associated with the substitutional doping for Ca2+ in the lattice which are responsible for the 645 nm emission of interest. Another inactive Eu2+ site based within a “EuO” type phase aggregated on the surface of the material is also identified, as well as competitive F+ center defects that are known to reduce emission from the Eu2+ sites. Intrinsic Mn2+ impurities are identified and used as local order probes to determine changes in ordering and symmetry upon cryo‐milling and heating treatments of the samples. X‐ray photoelectron (XPS) and photoluminescence (PL) spectroscopies are also conducted to complement the local structure observations. The reported data is useful in understanding how the nature of the lattice affects ground state electronic structure of functional defective sites, for the development of efficient and selective materials.
Highlights
It is the unique electronic structure of the f-block elements that is responsible for their desirable catalytic, magnetic and photophysical properties. These phosphors can be broadly claswhich are responsible for the 645 nm emission of interest
Eu2+ site based within a “EuO” type phase aggregated on the surface of the desired electronic transition and emission material is identified, as well as competitive F+ center defects that are known to reduce emission from the Eu2+ sites
The aim of this study was to provide a detailed characterization of the important photoluminescent species in CaS:Eu phosphors following a series of synthetic steps, and postsynthetic treatments, including grinding and heating, using variable frequency continuous wave (CW) electron paramagnetic resonance (EPR), XPS, and photoluminescence spectroscopy
Summary
Isolated Eu2+ sites are identified and associated with the substitutional doping for Ca2+ in the lattice. It is the unique electronic structure of the f-block elements that is responsible for their desirable catalytic, magnetic and photophysical properties. These phosphors can be broadly claswhich are responsible for the 645 nm emission of interest. Another inactive sified into two groups, based on the. Band width required; namely, broad band 5d → 4f interelectronic transitions possessing a short radiative lifetime (cf. 1 μs) and sharp emission bands arising from 4f → 4f intraelectronic transitions, that are
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