Strontium titanate, doped

The nature of the majority defects depends on the temperature and the partial pressure of oxygen. An example is given in Figure 11.4 in the case of strontium titanate doped with niobium. In reducing atmosphere (Po2 oxygen... 

Historically, materials based on doped barium titanate were used to achieve dielectric constants as high as 2,000 to 10,000. The high dielectric constants result from ionic polarization and the stress enhancement of k associated with the fine-grain size of the material. The specific dielectric properties are obtained through compositional modifications, ie, the inclusion of various additives at different doping levels. For example, additions of strontium titanate to barium titanate shift the Curie point, the temperature at which the ferroelectric to paraelectric phase transition occurs and the maximum dielectric constant is typically observed, to lower temperature as shown in Figure 1 (2). 

Strontium titanate [12060-59-2] SrTiO, becomes an n-ty e semiconductor when additional electrons are created on the Ti lattice sites by donor doping or when oxygen is removed from the material through heat treatment in a reducing atmosphere. The mobiUty of the electrons in the conduction band is about 6 crc] j(V-s). On the other hand, when ZnO is reduced, 2inc interstitials are formed and these act as donors, each yielding a free electron. 

Deliberate doping of strontium titanate by transition metal acceptors, including Mn, Fe, and Ni which concentrate at the grain boudaries, is known to enhance the GB capacitative effect and is an essential component for commercial materials. Calculations... 

Gunhold, A., Goemann, K., Beuermann, L. et al. (2003) Nanostructures on lanthanum-doped strontium titanate surfaces. Anal Bioanal Chem, 375 (7), 924-928. 

Moos, R. and Hardtl, K. H. (1997), Defect Chemistry of Donor Doped and Undoped Strontium Titanate Ceramics between 1000°C and 1400°C, Journal of the American Ceramic Society, 80,2549. 

Jeon, J.-H. and Kang, S.-J. L., Effect of sintering atmosphere on interface migration of niobium-doped strontium titanate during infiltration of oxide melts, J. Am. Ceram. Soc., 77, 1688-90, 1994. 

De Souza RA, Fleig J, Maier J, Kienzle O, Zhang Z, Sigle W, Riihle M (2003) Electrical and structural characterization of a low-angle tilt grain boundary in iron-doped strontium titanate. J Am Ceram Soc 86 922-928... 

Marina OA, Canfield NL, Stevenson JW (2002) Thermal, electrical, and electrocatalytical properties of lanthanum-doped strontium titanate. Solid State Ionics 149 21... 

Moos R, Hardtl KH (1997) Defect chemistry of donor-doped and undoped strontium titanate ceramics between 1000° and 1400 °C. J Am Ceram Soc 80 2549-2562... 

Balachandran U, Eror NG (1982) Electrical conductivity in lanthanum-doped strontium titanate. J Electrochem Soc 129 1021-1026... 

Zhao H, Gao F, Li X, Zhang C, Zhao Y (2009) Electrical properties of yttrium doped strontium titanate with A-site deficiency as potential anode materials for solid oxide fuel cells. Solid State Ionics 180 193... 

Figure 30.2 Band diagram of nitrogen-doped strontium titanate for hydrogen evolution. (Reproduced with permission from Ref. [34]. Copyright 2014 Elsevier.)...

As all metal oxides contain impurities, the defect mechanisms of pure oxides may subsequently be similar to that of doped oxides. For example, pure strontium titanate, SrXi03, has a similar defect chemistry to acceptor-doped SrTi03, because the impurities are usually metals that occur in lower oxidation states such as Fe +, Al +, Mg +, Na +, etc., and their concentrations, typically around 10 to 10 ppm, are sufficient to dominate the defect chemistry, especially at higher p02. 

Mg doped barium strontium titanate (BSTO) ceramics sintered from sol-gel-derived powders. /. Electroceram., 21 (1-4), 439-443. 

Nontransparent electrodes for example, lanthanum nickelate - La2Ni04, lanthanum-doped strontium titanate - Lai (Sr , Ti03... 

Hui, S. Petrie, Q. A. (2001). Electrical Properties of Yttrium-Doped Strontium Titanate under Reducing Conditions. Journal of Electrochemical Society. Vol. 149,... 

Perovskites have also been widely investigated as potential SOFC anode materials. Among these materials, chromites and titanates are promising [21, 22], Interesting results have been obtained with lanthanum strontium titanates [23] and especially cerium-doped lanthanum strontium titanate [24] however, it is now thought that the cerium-doped anodes are in fact two phases consisting of a ceria-perovskite assemblage [24],... 

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