Oxide ceramic materials, perovskite crystal structure

Fig. 8.3 Perovskite crystal structure of oxide ceramic materials used to fabricate composite membranes. A very large fraction of the metals in the periodic table can be substituted into the A and B lattice sites. A-sites contain larger cations such as alkaline earth and rare earths, including Ca, Sr and La, whereas the B-sites contain smaller transition metal cations such as H, Nb, V, Fe, Cr, Cu and Co. A near infinite variety of materials can be synthesized...

Toda K, Kameo Y, Kurita S, Sato M (1996) Crystal structure determination and ionic conductivity of layered perovskite compounds NaLnTiO (Ln = Rare Earth). J Alloys Compd 234 19-25 Tomchenko AA, Harmer GP, Marquis BT, AUen JW (2003) Semiconducting metal oxide sensor array for the selective detection of combustion gases. Sens Actuators B 93 126-134 Tongpool R, Leach C, Freer R (2000) Temperature and microstructural dependence of the sensitivity of heterocontacts between zinc oxide and copper oxide in reducing environments. 1 Mater Sci Lett 19 119-121 Traqueia LSM, Marques FMB, Kharton VV (2006) Oxygen ion conduction in oxide materials selected examples and basic mechanisms. Bol Soc Esp Ceram 45(3) 115-121... 

Various strategies were developed in the past for the synthesis of perovskite-structured oxides (Table 3.1). Of these, the choice of a particular method depends on the type of application expected. For catalytic applications, specific surfece area and crystal structure play crucial roles. Hence, the synthesis of these materials for catalytic applications always focused on obtaining crystalline materials with high values of specific surface area. The oldest method for the synthesis of perovskite-structured mixed metal oxides is the ceramic method. In this method, thoroughly mixed precursors (oxides, hydroxides, or carbonates) of the metals are calcined at elevated temperatures (>800 °C) for several hours. The surfece area of thus synthesized perovskites was, however, found to be less than 5m /g [5,30]. The high temperature used in solid-state reactions, for perovskite crystallization, results in the sintering of particles, which in turn leads to a large... 

H. Tagawa, J. Mizusaki, H. Nambu, C. Nakao, H. Takai, H. Minamiue, Crystal structure, phase relations and oxygen nonstoichiometry in perovskite type oxide Lai xSrxMn03. In Steele B.C.H. (ed.) Ceramic Oxygen Ion Conductors and Their Technological Applications, Brit. Ceram. Proceedings 56, pp. 113-123. Institute of Materials, London (1996)... 

The most commonly used and extensively studied cathode material in ceramic fuel cell is based on LaMn03 which is basically a perovskite oxide (ABO3) with p-type conductivity. In order to achieve a high electronic conductivity it is doped heavily by acceptor which leads to an enhanced hole concentration and the resultant conductivity is due to hopping of an electron hole between Mn " and Mn. It is doped at A-site or both at A- and B-sites with other cations. Normally cations with larger ionic radii (such as Ca ", Sr " ) are preferred to substitute at A-site and cations with smaller ionic radii (Co, Fe, Ni, Mn, Cr) preferred to occupy B-site. The crystal structure is a function of the composition which is solely dependent on A- and B-site dopant and on oxygen nonstoichiometry which is influenced by temperature and oxygen partial... 

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