Аннотация:In the present work, extensive studies of ionic conductors with pyrochlore and fluorite structures in the Gd2O3–HfO2 system are carried out. Gd2Hf2O7 and Gd2.1Hf1.9O6.95, Gd2.16Hf1.84O6.92, and Gd2HfO5 solid solutions known as “stuffed” pyrochlores were synthesized by mechanical activation of oxides followed by high temperature annealing at 1500–1600 °C. The main investigation methods were X-ray diffraction with Rietveld refinement, SEM microscopy and impedance spectroscopy in dry and wet air and N2. Proton conductivity was first found in Gd2HfO5 (1 × 10−6 at 600 °C), and solid solutions based on it, doped with lanthanum and calcium with pure fluorite structure. Proton conduction of the best proton-conducting ceramics Gd1.9La0.1HfO5 (3 × 10−6 at 600 °C) was confirmed by measurements in O2/D2O, Ar/D2O atmospheres. At all temperatures, the conductivity σD2O was lower than that of σH2O. Gd1.9Ca0.1HfO4.95 has a higher oxygen ion component of conductivity in dry air than Gd2HfO5, but the proton conductivity is the same. An attempt was made to synthesize the HEO composition (Lu0.2Y0.2Ho0.2Nd0.2La0.2)2HfO5, which turned out to be two-phase, containing ∼70% fluorite and ∼30% pyrochlore. The two-phase HEO (Lu0.2Y0.2Ho0.2Nd0.2La0.2)2HfO5 shows a total conductivity of ∼3 × 10−6 at 600 °C and ∼3 × 10−5 at 750 °C, respectively.
