Lanthanum-Containing Proton-Conducting Electrolytes with Perovskite Structures

Complex oxides with pronounced proton transfer occupy a special place in modern solid-state ionics and high-temperature electrochemistry, being of great interest from both fundamental and applied viewpoints. Doped barium cerate-zirconates (BaCeO3–BaZrO3) are positioned as the most conductive oxides, and therefore they are widely used in various solid oxide devices. However, the presence of a highly basic alkaline earth cation leads to an insufficient chemical stability of cerate-zirconates in real working conditions. In this regard, designing new proton-conducting oxides with improved chemical stability is an actual issue. Some lanthanum-containing perovskites, LaBO3 (where B is a trivalent element), can be considered as stable analogs since they contain no alkaline and alkaline earth elements in their basic structures. This review aims at a critical analysis of the properties of these compounds and the prospects for their application as electrolyte membranes for solid oxide fuel cells, pumps, and sensors. The paper provides basic information about LaBO3-based compounds, highlights their advantages in comparison with other representatives of proton conductors, and indicates disadvantages acting as limiting factors for the application of lanthanum-containing protonic electrolytes with a perovskite structure in electrochemical devices.