On the stabilities of the lower oxides of the rare earths

Spectral properties and self-reduction of Eu3+ to Eu2+ in aluminosilicate oxyfluoride glass

Eu-doped aluminosilicate oxyfluoride glass prepared via a melt-quenching method was investigated using X-ray diffraction, absorption spectroscopy, X-ray fluorescence spectrometry, photoluminescence spectroscopy and fluorescence decay curves. We found that the reduction of Eu3+ to Eu2+ ions occurred in the glass prepared in air. The emission spectra showed that the intensity of 4f65d → 4f7 transition of Eu2+ ions varied with increasing incident beam wavelength. Meanwhile, the fluorescence lifetimes of Eu3+: 5D0 → 7F2 monitored at 617 nm in the glass change with the variation of excitation wavelength. The energy transfer between Eu2+ and Eu3+ and the emission mechanisms of Eu2+ ions in the glass were also discussed.

Europium Anomaly in Plagioclase Feldspar: Experimental Results and Semiquantitative Model

The partition of europium between plagioclase feldspar and magmatic liquid is considered in terms of the distribution coefficients for divalent and trivalent europium. A model equation is derived giving the europium anomaly in plagioclase as a function of temperature and oxygen fugacity. The model explains europium anomalies in plagioclase synthesized under controlled laboratory conditions as well as the variations of the anomaly observed in natural terrestrial and extraterrestrial igneous rocks.