Abstract:
The solid solutions ŅeO$_2$–(Sm,Nd)$_2$O$_3$ have been prepared by the solid-phase synthesis. The microstructure, density, and electrical conductivity of ceramic samples obtained by rolling with an organic binder, followed by sintering in air at a temperature of 1600$^\circ$C have been investigated. The contributions to the total conductivity from the grain volume and grain boundaries in the temperature range of 250–700$^\circ$C have been separated using impedance spectroscopy. The impedance spectroscopy data have revealed a significant effect of grain boundaries on the transport properties of the solid electrolyte with a Sm dopant as compared to the electrolyte with Nd. The optical properties of the polycrystalline electrolytes Ce$_{1-x}$Nd$_x$O$_{2-\delta}$ and Ce$_{0.8}$Sm$_{0.2}$O$_{2-\delta}$ have been studied using Raman spectroscopy. In the spectrum of the ceramic samples, there are two modes: a mode of CeO$_2$ at a frequency of 465 cm$^{-1}$ and an additional mode at a frequency of $\sim$ 550 cm$^{-1}$ due to vibrations associated with oxygen vacancies, the intensity of which depends on the dopant concentration and the energy of the dopant cation–oxygen vacancy bond. The binding energy of oxygen vacancies in the fluorite structure correlates with the behavior of bulk conductivity, and the solid solutions with samarium exhibit the highest bulk conductivity.
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