Stability of the Structural and Transport Characteristics of (ZrO 2 ) 0.99-x (Sc 2 O 3 ) x (R 2 O 3 ) 0.01 (R-Yb, Y, Tb, Gd) Electrolytic Membranes to High-Temperature Exposure.

The effect of long-term high-temperature annealing on the phase composition, local crystal structure, and oxygen-ion conductivity of SOFC membranes based on zirconium dioxide solid solutions was studied. Crystals with the composition of (ZrO 2 ) 0.99-x (Sc 2 O 3 ) x (R 2 O 3 ) 0.01 (where x = 0.08-0.1; R-Yb, Y, Tb, Gd) were obtained by the method of directed melt crystallization in a cold crucible. The crystals were annealed in air at a temperature of 1000 °C for 400 h. The phase analysis of the crystals before and after annealing was studied by X-ray diffractometry and Raman spectroscopy. The study of the ionic conductivity of the crystals was carried out by the method of impedance spectroscopy in the temperature range 400-900 °C. It has been shown that when various rare earth cations (Yb, Y, Tb, and Gd) are used, the maximum conductivity is observed for the compositions (ZrO 2 ) 0.91 (Sc 2 O 3 ) 0.08 (Yb 2 O 3 ) 0.01 , (ZrO 2 ) 0.89 (Sc 2 O 3 ) 0.1 (Y 2 O 3 ) 0.01 , (ZrO 2 ) 0.90 (Sc 2 O 3 ) 0.09 (Tb 2 O 3 ) 0.01 , and (ZrO 2 ) 0.89 (Sc 2 O 3 ) 0.1 (Gd 2 O 3 ) 0.01 . At the same time, these crystals have a highly symmetrical pseudocubic structure, which is retained even after crystal annealing. At comparable concentrations of Sc 2 O 3 , the conductivity of crystals decreases with an increase in the ionic radius of the rare earth cation. The high-temperature degradation of the conductivity is also discussed depending on the type of rare earth oxide and the concentration of scandium oxide.