Quantitative determination of site occupancy of multi-rare-earth elements doped into Ca2SnO4 phosphor by electron channeling microanalysis

X-ray fluorescence analysis based on electron channeling effects in transmission electron microscopy (TEM) was performed on Ca2SnO4 phosphor materials doped with Eu3+/Y3+ at various concentrations, which showed red photoluminescence associated with the 5D0–7F2 electric dipole transition of Eu3+ ions. The method provided direct information on which host element site dopant elements occupy, the results of which were compared with those of X-ray diffraction (XRD)–Rietveld analysis. The obtained results indicated that while it is not favorable for a part of Eu3+ to occupy the smaller Sn4+ site, this is still energetically better than creating Ca vacancies or any other of the possible charge balance mechanisms. The local lattice distortions associated with dopant impurities with different ionic radii were also examined by TEM–electron energy-loss spectroscopy (TEM–EELS). The change in PL intensity as a function of dopant concentration is discussed based on the experimental results, although the general concept of concentration quenching applies.

The composition of Ca1.8Eu0.2Y0.2Sn0.8O4 determined by electron channeling microanalysis is graphically shown, where the rare-earth dopants, Eu and Y preferentially occupy the Ca and Sn sites, respectively, to maintain the local charge neutrality.Figure optionsDownload as PowerPoint slide