Phase formation in ternary systems of sodium, rare-earth (scandium, indium, and ytterbium), and boron oxides
Year: 2025
Type: article
Abstract: The study was aimed at examining phase equilibria in Na2O–R2O3–B2O3 systems (R = In, Sc, Yb). Interactions in these systems were analyzed using the solid-state reaction method. Phase formation in the ternary systems of sodium, rare-earth (scandium, indium, and ytterbium), and boron oxides was studied for the first time in the subsolidus region within the temperature range of 700–750°С. Preliminary triangulation of the analyzed systems was conducted. At 750°С, the isothermal cross sections of Na2O–R2O3–B2O3 (R = In, Sc, Yb) systems are represented by eight, thirteen, and eleven triangles of coexisting phases, respectively. The study confirmed the formation of three known double sodium-scandium borates in the Na2O–Sc2O3–B2O3 system: Na3Sc(BO3)2, Na3Sc2(BO3)3, and NaScB2O5. Also, a double sodium-scandium borate of approximate composition Na3ScB8O15 was found to form, which was indexed as monoclinic (approximate space symmetry group Cc). The unit cell parameters were refined using the Le Bail method: a = 12.625(6); b = 7.725(2); c = 10.409(3), β = 53.19(2)°. The Na2O–Yb2O3–B2O3 system contains three new double borates: Na3Yb(BO3)2, Na3YbB8O15, and borate with a composition close to the stoichiometric ratio Na2O•Yb2O3•B2O3. The formation of the following compounds was first experimentally shown: Na3YbB8O15 isostructural to Na3GdB8O15 and isoformula Na3Yb(BO3)2, which is not isostructural to Na3Y(BO3)2. The triple oxide system with indium was found to be eutectic, i.e., without the formation of double sodium-indium borates.
DOI: 10.21285/achb.974
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: diamond
Award: G227251437
OpenAlex ID: W4410776977