Recent advances in perovskites: Processing and properties

Abstract

The perovskite structure is one of the most wonderful to exist in nature. It obeys to a quite simple chemical formula, ABX3, in which A and B are metallic cations and X, an anion, usually oxygen. The anion packing is rather compact and leaves interstices for large A and small B cations. The A cation can be mono, di or trivalent, whereas B can be a di, tri, tetra, penta or hexavalent cation. This gives an extraordinary possibility of different combinations and partial or total substitutions, resulting in an incredible large number of compounds. Their physical and chemical properties strongly depend on the nature and oxidation states of cations, on the anionic and cationic stoichiometry, on the crystalline structure and elaboration techniques, etc. In this work, we review the different and most usual crystalline representations of perovskites, from high (cubic) to low (triclinic) symmetries, some well-known preparation methods, insisting for instance, in quite novel and original techniques such as the mechanosynthesis processing. Physical properties are reviewed, emphasizing the electrical (proton, ionic or mixed conductors) and catalytic properties of Mn- and Co-based perovskites; a thorough view on the ferroelectric properties is presented, including piezoelectricity, thermistors or pyroelectric characteristics, just to mention some of them; relaxors, microwave and optical features are also discussed, to end up with magnetism, superconductivity and multiferroisme. Some materials discussed herein have already accomplished their way but others have promising horizons in both fundamental and applied research. To our knowledge, no much work exists to relate the crystalline nature of the different perovskite-type compounds with their properties and synthesis procedures, in particular with the most recent and newest processes such as the mechanosynthesis approach. Although this is not intended to be a full review of all existing perovskite materials, this report offers a good compilation of the main compounds, their structure and microstructure, processing and relationships between these features