Synthesis of Ba 4 R 3 F 17 (R stands for rare-earth elements) powders and transparent compacts on their base
Single-phase samples of Ba4R3F17 · nH2O (R = La, Ce, Pr, Nd, Eu, Gd, Y, Er, or Yb; n = 2.5−3.2) were prepared by coprecipitation from nitrate solutions using hydrofluoric acid. The phases crystallize in a fluorite-type
face-centered cubic lattice. The dried precipitates are transparent. Scanning electron and atomic-force microscopy and X-ray
diffraction line broadening show a hierarchic structure in the samples: primary nanoparticles join into agglomerates with
characteristic sizes of about 150–200 nm, these agglomerates being self-packed into parallel layers with a thickness on the
order of 500 nm.