Crystal chemistry, stability and properties of interlanthanide perovskites: A review

In this review structural features, stability issues and physical properties of the eleven interlanthanide perovskites prepared at atmospheric pressure are surveyed and discussed. Due to the reduced size difference between cations, the structure of these oxides is strongly distorted with respect to the ideal cubic case. Therefore, in structure maps they are located close to the boundary of the perovskitic stability field; an interesting correlation between stability and the Goldschmidt tolerance factor t shows that the perovskitic temperature range narrows with decreasing t. Magnetic and optical properties are strictly related to the presence of 4f electrons, that determine the existence of many discrete energy levels. Acceptor-doped LaYO3 and LaYbO3 are comparable in terms of protonic conductivity to the well known cerates, and thanks to their better chemical stability against CO2, they are a good alternative to the latter in solid oxide fuel cells. The high dielectric constant of some interlanthanide perovskites makes them interesting candidates as gate oxides in MOSFETs.