Incorporation of Europium into (Ba,Ca)2(CO3)2

Synchrotron-based powder diffraction measurements in combination with inductively coupled plasma optical emission spectrometry, Raman and fluorescence spectroscopy show that (Ba,Ca)2(CO3)2 can incorporate significant amounts (up to 6 ​mol%) of europium. This solid solution is therefore of potential interest for the solidification of nuclear waste streams involving aqueous nitrate solutions of lanthanides. Europium replaces Ba/Ca on lattice sites and is not incorporated as an interstitial defect. Charge compensation is likely due to the presence of OH−-groups as we could exclude a coupled substitution involving Na+. The Eu-containing compound is stable to at least 723 ​K. We show that the one-phase-field of (Bax,Ca(1−x))CO3 solid solutions at ambient conditions is larger (0.36 更多