Wavelength dispersive x-ray fluorescence spectrometry for the analysis of laser active lanthanides (Ln) in NaT1−xLnx(WO4)2 crystals

Four crystals with nominal compositions, NaLa0.95Tm0.05(WO4)2 (1.32 wt% of Tm), NaGd1−xTmx(WO4)2x = 0.05, 0.07 (1.24 and 1.32 wt% of Tm, respectively) and NaY0.9Yb0.1(WO4)2 (2.81 wt% of Yb), were analyzed by wavelength dispersive x-ray fluorescence spectrometry. A procedure for sample preparation was developed using lithium tetraborate as flux to obtain glass disks and to circumvent precipitation problems of lanthanides and tungsten experienced in their dissolution by wet routes. For this purpose three specific calibration standards with pure oxides were prepared for each analyzed element with near to constant W and Na concentrations, so that matrix effects could be properly addressed. The procedure allows measurement of the Tm and Yb concentrations above the determination limits of 0.017 wt% and 0.042 wt% for Tm in the first two crystals, respectively, and of 0.039 wt% of Yb in the last one. Further analyses show an excess with regard to the nominal formula of ≈5 mol% in the total concentration of trivalent ions incorporated to the crystal and some deficiency of Na (≈10 mol%) and W (≈2 mol%) ions. Copyright © 2009 John Wiley & Sons, Ltd.