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, ABX 3 , 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 multiferroïsme.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.

Development of a Control Method for Conduction and Magnetism in Molecular Crystals

“…It has been concluded that atmosphere itself does not matter in irradiation effects on α; the important factor is whether sufficient energy is provided or not by light and/or heat. They were characterized by elemental analysis (Table 2), high resolution solid-state 13 C NMR (powder) (Figure 8), 100 IR absorption (KBr) spectra, 104,105 UVvis diffuse reflectance spectra (KBr), 104,105 MALDI-TOF MS (Figure 9), 100 N 1s and Ag 3d XPS (Figure 10), 103 Ag MNN Auger spectra (Figure 11), Ag L 3 X-ray absorption near edge structure (XANES) (Figure 12), 99,101 Ag extended X-ray absorption fine structure (EXAFS) (Figure 13), 101 electrical resistivity (Figure 14), magnetic susceptibility (Figure 15), 80,81,105 and X-ray diffraction (XRD) powder patterns ( Figure 16). The Ag + ions are generally known to respond to UV, but their actual photochemistry sensitively depends on coexistent chemical species.…”

Organometal Trihalide Perovskites with Intriguing Ferroelectric and Piezoelectric Properties

“…Piezoelectricity was discovered by Pierre and Jacques Curie in 1880 while studying the effect of pressure on the generation of electrical charges by some natural crystals . Piezoelectric materials can undergo a phase transition where the centrosymmetric cubic structure transfers to the first low‐symmetry structure exhibiting a spontaneous polarization, occurring at a certain temperature which is defined as the Curie temperature ( T c ) . A characteristic example of a structure which exhibits a spontaneous polarization with a certain Curie temperature is the perovskite‐type structure of ABX 3 .…”

Synthesis and Characterization of Ba0.5Sr0.5NixCo0.8‐xFe0.2O3‐δ (x=0 and 0.2) Perovskites as Electro‐catalysts for Methanol Oxidation in Alkaline Media

“…The physical and chemical properties and the catalytic activities of these perovskites are greatly affected by the nature, oxidation states and the stochiometry of the elements of A and B . Their compositions, with different combinations of charged cations in the A and B sites (A cation can be mono, di or trivalent, whereas B can be a di, tri, tetra, penta or hexavalent cation) , can be varied over a wide range by partial or total substitutions with a great range of metal cations, the resulting formula is in form ( are substituted cations) . Conventionally in the literature, Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3‐δ perovskites oxides containing barium (Ba), strontium (Sr), Cobalt (Co) and iron (Fe) are labeled by BSCF symbol.…”

“…The perovskite family of materials constitutes an important class of semiconductors [9,10] exhibiting properties suitable for numerous applications, such as electrode materials for solid oxide fuel cells (SOFCs), oxygenpermeating membranes, thermoelectric devices [11], sensors, fuel cells [12] and catalysis in oxidation and reduction processes [13,14]. Recently, oxides with perovskite structure have been extensively studied as catalysts in methanol oxidation reaction in acid and alkaline media, due to [ their variety of properties, such as excellent proton transport property, thermal and chemical stability, mechanical, electrical and catalytic properties [11][12][13][14][15] Generally, the crystallographic structural of perovskite-type oxides with the general formula ABO 3 (A: an alkaline earth or a lanthanide metal and B: a transition metal) is presented by a flexible and corner-connected BO 6 octahedral network where B cations are coordinated by 6 oxygen anions, while A cations are coordinated by 12 oxygen anions [12,16]. The physical and chemical properties and the catalytic activities of these perovskites are greatly affected by the nature, oxidation states and the stochiometry of the elements of A and B [17,18] [20,21].…”