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Phase eqilibria in the systems rare earth elements


Presented Frantsevich Institute for Problems of Materials Science NAS of Ukraine.

Chudinovych Olga Vasylivna

Using the methods of physicochemical analysis (XRD, petrography, SEM, X–ray microprobe analysis) phase equilibria were firstly investigated in the ternary systems La2O3–Y2O3–Ln2O3, where Ln = Nd, Sm, Eu, Gd, Yb. The isothermal sections for these systems at 1500 and 1600 °C were developed. Phase equilibria in the boundary binary system La2O3–Yb2O3 were studied for the first time in the temperature range 1100–1600 °C. Phase boundaries were refined fields in the binary system Nd2O3–Y2O3 at 1500–1600 °C.

The isothermal sections for the ternary La2O3–Y2O3–Ln2O3 (Ln = Nd, Sm, Eu, Gd, Yb) systems at 1500 and 1600 °C were developed. The solid solutions based on various polymorphous forms of constituent phases and ordered phase with a structure of the perovskite-type of  LaYO3, LaYbO3 were revealed in the systems. The main regularities of the phase diagrams for the ternary La2O3–Y2O3–Ln2O3 (Ln = Nd, Sm, Eu, Gd) systems at 1500 and 1600 °C are shown. The solid solutions are formed by the mechanism of the isovalent substitution. The stability of ordered phases and solid solutions are determined by the dimensional factor: in the LaYO3, the large size Nd3+ ions replace La3+ ions, the smaller ions of the cerium series Sm3+, Eu3+, Gd3+ substitute both Y3+ and  La3+, whereas all the mentioned rare earth ions maybe replaced by Y3+ ions.

The main regularities of the phase reactions in the solid state have been revealed depending on lanthanide ionic radius. Basing on the established feature of phase diagram constitution of the ternary systems La2O3–Y2O3–Ln2O3 it was found that with decreasing ionic radius of lanthanide the homogeneity range of R-phase decreases. The obtained data are of scientific basis for the development of new materials for structural and functional applications in energy, medicine, ceramics, glass production and others.

Number of publications: 13 papers in international and national professional journals, in English-language journal 1 with impact factor of 0.976 and 20 abstracts at scientific conferences. Total sum of the times cited - 1 (according to the Google Scholar database), h-index - 1.