Ceria-zirconia oxides is thermodynamically favorable in a wide range of solid solution compositions, which means that ceria-zirconia is metastable with respect to phase separation. Ceria-zirconia is widely used as a component in current three-way catalytic converters. The ceria-based component of the converter has several functions, including promoting the dispersion of the noble metals in the catalyst, but also storing and releasing oxygen. The incorporation of zirconium in modern converters, forming ceria-zirconia, improves the performance of the catalyst by enhancing the resistance of the material to sintering, and simultaneously increasing the ability of the oxide to accommodate oxygen vacancies in its structure.
Synthetic element synthesis, so the concept of natural isotope abundance has no meaning. Therefore, for synthetic elements the total nucleon count (protons plus neutrons) of the most stable isotope, i.e. the isotope with the longest half-life—is listed in brackets as the atomic mass. The first element discovered through synthesis was technetium—its discovery being definitely confirmed in 1936. This discovery filled a gap in the periodic table, and the fact that no stable isotopes of technetium exist explains its natural absence on Earth (and the gap). With the longest-lived isotope of technetium, Tc-98, having a 4.2-million-year half-life, no technetium remains from the formation