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This document resumes the activity of the Italian CRG beamline at ESRF (LISA project) during year 2022. The latest news from the beamline are presented as well as details on the technical activity, highlight expe-riments and publications.

An experimental investigation of the crystallographic, Raman and transport properties of the Ce1−x(Nd0.74Tm0.26)xO2−x/2 (0.1 ≤ x ≤ 0.6) doped ceria system was performed with the aim of setting out correlations between structural features and ionic conductivity of the material. The chosen composition ensures that the average size of the Nd3+ and Tm3+ doping ions coincides with the one of Sm3+; even so, the studied system presents larger cell parameters and a wider compositional extent of the CeO2-based solid solution than Sm-doped ceria. Moreover, the occurrence of two different activation energies to ionic conduction below and above ~750 K determines the existence of two distinct conduction regimes. The described experimental results agree with the formation below the threshold temperature of 1 V O . . 2 T m C e ' trimers, which promote the incorporation of Nd C e ' isolated defects into the CeO2-based solid solution. In the high temperature range the dissociation of trimers induces the appearance of a lower activation energy; the extrapolation of its value at infinite dilution provides a result in good accordance with the expected binding energy of 1 V O . . RE C e ' dimers, pointing at their stability even in the high temperature conduction regime.

Defect aggregates in doped ceria play a crucial role in blocking the movement of oxygen vacancies and hence in reducing ionic conductivity. Nevertheless, evaluation of their amount and the correlation between domain size and transport properties is still an open issue. Data derived from a high-pressure X-ray diffraction investigation performed on the Ce1–x(Nd0.74Tm0.26)xO2–x/2 system are employed to develop a novel approach aimed at evaluating the defect aggregate content; the results are critically discussed in comparison to the ones previously obtained from Sm- and Lu-doped ceria. Defect clusters are present even at the lowest considered x value, and their content increases with increasing x and decreasing rare earth ion (RE3+) size; their amount, distribution, and spatial correlation can be interpreted as a complex interplay between the defects’ binding energy, nucleation rate, and growth rate. The synoptic analysis of data derived from all of the considered systems also suggests that the detection limit of the defects by X-ray diffraction is correlated to the defect size rather than to their amount, and that the vacancies’ flow through the lattice is hindered by defects irrespective of their size and association degree., A novel approach to the treatment of high-pressure X-ray diffraction data is applied to several rare earth-doped ceria systems with the aim of providing an evaluation of the amount of defect aggregates and of the composition of the CeO2-based solid solution. By this method, it is possible to effectively correlate the structural properties and ionic conductivity of the studied material.

The structural, microstructural, Raman and ionic conductivity properties of (Gd,Sm)-doped ceria were studied and compared to the ones of similar ceria systems with the aim of deepening the comprehension of the correlations between defect chemistry and movement of oxygen vacancies in such materials, which are ideal candidates as electrolytes in solid oxide cells. The system was chosen as it combines the advantages of using the most effective doping ions for ceria, namely Sm

Rare earth-doped ceria thin films are currently thoroughly studied to be used in miniaturized solid oxide cells, memristive devices and gas sensors. The employment in such different application fields derives from the most remarkable property of this material, namely ionic conductivity, occurring through the mobility of oxygen ions above a certain threshold temperature. This feature is in turn limited by the association of defects, which hinders the movement of ions through the lattice. In addition to these issues, ionic conductivity in thin films is dominated by the presence of the film/substrate interface, where a strain can arise as a consequence of lattice mismatch. A tensile strain, in particular, when not released through the occurrence of dislocations, enhances ionic conduction through the reduction of activation energy. Within this complex framework, high pressure X-ray diffraction investigations performed on the bulk material are of great help in estimating the bulk modulus of the material, and hence its compressibility, namely its tolerance toward the application of a compressive/tensile stress. In this review, an overview is given about the correlation between structure and transport properties in rare earth-doped ceria films, and the role of high pressure X-ray diffraction studies in the selection of the most proper compositions for the design of thin films.