Interaction of Lanthanum, Lutetium, and Ytterbium Oxides at 1600°C

• Published in: Powder metallurgy and metal ceramics 2021-09, Vol.60 (5-6), p.337-345
• Main Authors: Chudinovych, O.V., Bykov, O.I., Samelyuk, A.V.
• Format: Article
• Language: English
• Subjects: Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Composition; Diffraction; Glass; Heat treatment; Homogeneity; Lanthanides; Lanthanum; Lanthanum oxides; Lattice parameters; Lutetium; Lutetium oxide; Materials Science; Metallic Materials; Natural Materials; Oxides; Perovskite; Perovskites; Phase diagrams; Phase equilibria; Physicochemical Materials Research; Room temperature; Shape factor; Solid solutions; Solubility; X ray powder diffraction; X-rays; Ytterbium
• ISSN: 1068-1302; 1573-9066
• DOI: 10.1007/s11106-021-00248-8

Phase equilibria in the La 2 O 3 –Lu 2 O 3 –Yb 2 O 3 system were studied by X-ray diffraction and electron microscopy for the first time at 1600°C over the entire composition range. Solid solutions based on various crystalline modifications of the starting components and ordered perovskite-type phases were found to form in the system. The starting materials were La 2 O 3 , Lu 2 O 3 , and Yb 2 O 3 (99.99%). The samples were prepared with a concentration step of 1–5 mol.%. Weighed oxides were dissolved in HNO 3 (1 : 1) and then the solutions were evaporated and decomposed at 800°C for 2 h. The samples were heat treated in three stages: at 1100°C (for 163 h), at 1500°C (for 70 h), and at 1600°C (for 10 h) in air. The samples were subjected to X-ray powder diffraction employing a DRON-3 diffractometer at room temperature (Cu-K α radiation, Ni filter). The scan angle was 0.05–0.1° in the range 2θ = 15–90°. The isothermal section of the La 2 O 3 –Lu 2 O 3 –Yb 2 O 3 phase diagram at 1600°C shows three single-phase (A-La 2 O 3 , R, C-Lu 2 O 3 (Yb 2 O 3 )) and two two-phase (C + R, A + R) regions. The system forms continuous areas of solid solutions based on the cubic modification of C-Lu 2 O 3 (Yb 2 O 3 ) and the ordered perovskite-type phase (R phase). The solubility limits were determined and composition dependences for lattice parameters of the phases formed in the system were plotted. The boundary solubility of lutetium oxide in the R phase is 5 mol.% in the Lu 2 O 3 –(50 mol.% La 2 O 3 –50 mol.% Yb 2 O 3 ) section. The homogeneity range of the C-Lu 2 O 3 solid solutions extends from 93 to 100 mol.% Lu 2 O 3 in the Lu 2 O 3 –(50 mol.% La 2 O 3 –50 mol.% Yb 2 O 3 ) section. The solid solutions form through isovalent substitution, and the stability of ordered phases and solid solutions is determined by the shape factor of lanthanides.