| Popis: |
The phase formation of compounds in the ternary BaOCaOY 2 O 3 system at 1300 and 1450 °C was studied by X-ray diffraction. The formation of BaCa 2 Y 6 O 12 is reported for the first time at these low temperatures and its existence region is determined. Isomorphous BaCa 2 Ln 6 O 12 compounds were found to exist for the smaller lanthanide ions (Ln Sc, In, Dy, Ho, Er, Tm, Yb, Lu). The luminescence of europium- and terbium-activated BaCa 2 Y 6 O 12 was investigated. It is deduced that the activator ions are incorporated on two different sites in the host lattice. The efficiencies, both for cathode-ray excitation and UV excitation, are low. The europium-doped compound was also characterized using 151 Eu Mossbauer spectroscopy; the results indicate the absence of Eu 2+ ions in the lattice and support the presence of Eu 3+ ions on two different crystallographic sites. |
