Perovskite families

Eng HW, Barnes PW, Auer BM, Woodword PM (2003) Investigation of the electronic structure of d° transition metal oxides belonging to the perovskite family. J Solid State Chem 175 94-109... 

O. Gourdon, V. Petricek and M. Evain, A new structure type in the hexagonal perovskite family structure determination of the modulated misfit compound SiyigTiSj, Acta Crystallogr., B56, 409-418 (2000). 

The perovskite-type structure offers to materials science some of the most versatile and important building modules. Many members of the perovskite family and their derivative stmctures play a fundamental role in several technical applications because they display diverse properties in such fields as electromagnetism, optics, catalysis, composite and porous materials. 

To some extent the multiplicity of phases that belong to the perovskite family can be rationalised by assuming that perovskites are simple ionic compoimds, where A is usually a large cation, B is usually a medium-sized cation and X is an anion. 

Subsequently we present the main experimental results about size effects of different physical properties of nanoferroelectrics with perovskite structure [16]. Latter ferroelectrics constitute large group of the materials with structure ABO3. The majority of them have wide band gap so that pure samples (i.e. those without specially added impurities) are almost ideal insulators. Note that the predominant part of modern technological applications of ferroelectrics belong to the substances of perovskite family. 

The perovskite family is one of the most important representative among a large variety of inorganic compoimds. The majority of chemical elements from the periodic table can form ABX3 compounds with the perovskite structure (Goodenough and Longo, 1970 Goodenough, 1971 Fesenko, 1972 Reller, 1993 Woodward,... 

The perovskite family is a typical representative of complex oxides. Many of the perovskites exhibit interesting physics that includes ferro- and piezoelectricity, high electronic and ionic conductivities, diverse magnetism, colossal... 

The perovskite families are characterized by the great flexibility of their crystal structures so as to accommodate wide cation substitutions or anion vacancies, and... 

Such membranes rely upon the ability of the oxide material to selectively transport defects which themselves undergo catalytic reactions at the free membrane surfaces. We focus on the versatile perovskite family of metal oxides which exhibits both ionic and electronic conductivity (pure ion conductors or solid electrolytes are dealt with elsewhere in this book). 

It is far beyond the scope of this chapter to review the electronic structures and properties of all metal oxides, or even all of the important metal oxide stmc-ture types. Instead, this section covers some featnres of one stmctural family, perovskite, in some detail. In doing so, it is hoped that the important concepts will be illnstrated in snch a way that they can be widely appUed. Of course, the choice of the perovskite stmctnre as an illnstrative example is not a random choice. The perovskite family of componnds is very extensive, encompassing most of the periodic table. Fnrthermore, perovskites exhibit nearly every type of interesting electronic or magnetic behavior seen in oxides (ferromagnetism, ferroelectricity, piezoelectricity, nonlinear optical behavior, metaUic condnctivity, snpercondnct-ivity, colossal magnetoresistance, ionic conductivity, photoluminescence, etc.). One important property that is not readily found among perovskites, transparent conductivity, is the focus of Section 6.7. 

Despite large research efforts devoted to interconnects during the last decade, there is still no component that satisfies all the above requirements. At present, the most signifieant interconnection material is doped LaCrOj which belongs to the perovskite family ABO3. Two major problems are still to be solved (i) thermal expansion mismatch with zirconia (ii) poor sinterability in oxidizing conditions. 

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