Phase Relations In The System Ternary Based On Ceria, Zirconia And Ytterbia At 1500 Degrees C

Based on the results of studying the synthesized samples by X-ray phase analysis, the isothermal section of the ZrO2-CeO2-Yb2O3 system at 1500 degrees C has been constructed. In this temperature new ordering of intermediate phases was not confirmed. It was established that in the system there exist fields of solid solutions based on tetragonal (T) modification ZrO2, cubic (C) modification Yb2O3 and cubic with fluorite-type structure (F) modifications CeO2 (ZrO2), as well as intermediate phase with orhombohedral structure Zr3Yb4O12 (delta) were determined. The maximal solubility of ceria in delta- phase is 12 mol. % be along the section CeO2-(60 mol % ZrO2-40 mol % Yb2O3). The refined lattice parameters of the unit cells for solid solutions of compositions for the systems were determined. In the zirconia-rich corner, the solid solutions based on tetragonal modification of ZrO2 are formed. The solubility of Yb2O3 in the T-ZrO2 is low and amounts to similar to 0.5 mol %, as evidenced by XRD analysis results. The solid solutions based on tetragonal modification of zirconia cannot be quenched from high temperatures due to low stability of T-ZrO2 under cooling with furnace conditions. The diffraction patterns recorded at room temperatures included the peaks of monoclinic phase M-ZrO2. The lattice parameters of the intermediate phase with orhombohedral structure Zr3Yb4O12 (delta) vary from a = 0.9654 nm, c = 0.8935 nm for the composition, containing 59.4 mol % ZrO2-1 mol. % CeO2-39.6 mol % Yb2O3 to a = 0.9742 nm, c = 0.9012 mn for the composition (F + delta), containing 51 mol % ZrO2-15 mol % CeO2-34 mol % Yb2O3 and to a = 0.9759 nm, c = 0.9028 nm for the composition (F + C + delta), containing 48 mol % ZrO2-20 mol % CeO2-32 mol % Yb2O3. The isothermal section of the ZrO2-CeO2-Yb2O3 system at 1500 degrees C contains one three-phase region (F+C+delta), four single-phase regions (F-CeO2(ZrO2), T-ZrO2, delta, C-Yb2O3) and four two-phase regions (C+F, C+delta, F+delta, F+T).