Co-precipitation of barium and yttrium fluorides from aqueous solutions at room temperature produced non-equilibrium Ba1−xYxF2+x nanofluoride phase with face-centered cubic crystal lattice of fluorite-type with the composition interval of the homogeneity for x=0.35–0.75. Lattice parameter a of this solid solution nanophase varied as a function of the sample chemical composition in a complex manner with two areas of linear dependency, from x=0.35 to 0.45 and from x=0.50 to 0.75. A plausible explanation of this phenomenon included a change of the type of crystal lattice defects and the manner of their population with the corresponding ions. An increase of the relative amount of yttrium in the HF reaction system led to the formation of hydroxonium salt of decafluorotriyttrium acid, (H3O+)Y3F10−·nH2O, instead of expected YF3 hydrate. No formation of oxyfluoride phases under acidic conditions has been observed.

Reactions of solutions of yttrium oxide in nitric acid with a 1.67 M NH4HCO3 solution were studied by direct and back titration. When the concentration of the reacting solution was within 0.031–0.052 mol/L (as Y2O3), yttrium carbonate Y2(CO3)3 · nH2O (n ≈ 2.5) of fibrous or spherulitic morphology precipitated. When the concentration was decreased to 0.022 mol/L, a new phase of platy morphology appeared. Heating these precipitates to 650–680°C yielded yttrium oxide having coherent scattering domain sizes of 40–80 nm. Y2O3 particles retain the precursor morphology.

С использованием прямого и обратного титрования исследовано взаимодействие растворов оксида иттрия в азотной кислоте с 1.67 М раствором NH4HCO3. При концентрации исходного раствора 0.031–0.052 моль/л (в расчете на Y2O3) в осадок выпадает карбонат иттрия Y2(CO3)3 · nH2O (n 2.5) волокнистой или сферолитной морфологии. При уменьшении концентрации до 0.022 моль/л образуется новая фаза пластинчатой морфологии. Нагревание осадков до 650–680°С приводит к образованию оксида иттрия с размером областей когерентного рассеяния 40–80 нм. Частицы Y2O3 сохраняют морфологию прекурсоров.

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.