EPR spectra of Gd(3+) as probe of small-polarons hopping regime

In the past few years, CeO2-based materials have been intensively studied as catalysts and electronic promoters for heterogeneous reactions or oxide ion conducting materials for electrochemical devices. All those applications presume preparation of fine powders adapted for making bulk ceramics, coatings, films and composites. In our case the solid electrolyte is a key component for solid-state electrochemical devices, such as SOFC having an increasing importance in stationary fuel cell application. The doped cerium electrolytes have elevated ion conductivity in respect to the conventional YSZ and may operate at lower temperatures (< 900K). Synthesis using wet chemistry, often called the “chemical route”, can provide good homogeneity of the raw materials due to the reagents mixing occurs at the molecular level. The resulting oxide powders have a high specific surface area and, consequently, a high beneficial reactivity. To obtain that powders an acrylamide polymerisation supported techniques was used fo the synthesis of Ce1-xGdxO(4-x)/2 nanopowders. Different Ce1-xGdxO(4-x)/2 (x = 0.1; 0.2) nanopowders were analysed by EPR spectroscopy to select the doping level, which minimise the probability electronic conductivity occurrence. Thus, it was shown that the conductivity of the samples is directly related with oxygen content in the nanopowder. The conductivity of the samples, calculated on the base of the EPR spectra and its trend vs. temperature was studied in details. On the base of the obtained results were selected optimal composition of the nanopowders, which were pressed and sintered at high temperature for preparation a high density ceramic materials (rel  96%). An electrochemical properties of the materials thus obtained were studied.