Crystal structure and unstable valence in a novel intermetallic phase Ce2Ru2Al

Mixed Valence of Ce and Its Consequences on the Magnetic State of Ce9Ru4Ga5: Electronic Structure Studies

“…Remarkably, in both compounds one of the different Ce atoms is coordinated by its Ru neighbors at a distance of ∼ 2.2 Å and ∼ 2.4 Å, respectively, which is much shorter than the sum of the covalent radii of the Ce and Ru atoms. As discussed in detail in a series of our previous papers on the Ce-Ru-X intermetallics (X = Ge, Ga, Al) [15][16][17][18][19][20][21][22], strong Ce-Ru bonding brings about a significant instability of the electronic 4 f shell, and thus intermediate valence behavior may arise. At the same time, the Ce ions with Ce-Ru distances of regular length remain their trivalent character that promotes localized magnetism with possible magnetic ordering at low temperatures.…”

In Situ Control of the Eluted Ni Nanoparticles from Highly Doped Perovskite for Effective Methane Dry Reforming

“…To solve this drawback, previous studies have suggested an augmented space for Ni doping through doping on relatively bigger Ce (IV) (Å = 0.87) [24] in the perovskite lattice, resulting in an ion radius increase for doped Ni species by a large amount (i.e., over 13 wt%) [25,26]. However, Ce generally contains an unstable orbital shell which has a large change in the intermediate valence depending on the environment, so it is thermodynamically unstable [27]. This is one reason why major studies have been conducted on the exsolution of Ni NPs on Sr-doped perovskites in changing reduction temperatures [28].…”