Lanthanum Titanates

Perovskite structures of rare earth titanate oxides are of considerable interest in recent years [63,64], Among different rare earth metals, lanthanum was the most investigated. In order to accommodate the excess oxygen, the replacement of divalent cations such as Ca or Sr in general perovskite materials by a tri-valent cation such as La resulted in excess electrons and slabs of a distorted perovskite structure. With the highly donor-doped (110) perovskite, the separation of electrons and holes is more facile than other semiconductor materials because of a narrower depletion layer and a more drastic band bending. In this way the activity of the photocatalytic processes were improved. As obviously, to suppress the recombination of the generated electrons and holes is an important condition [63,64]. 

Doping of La2Ti207 with alkaline-earth (Ca, Sr, or Ba) species followed by the deposition of Ag [71] or NiO/Ni [10,72] led to photocatalysts active for CO2 reduction with water as reducing agent [71]. However, the activity reached a 

I 2La2Ti30io modified with V [77], Zn [78], Nb (and protonated derivatives) [79], Fe , W , Ni [80], or sensitized with CdS [81] showed improved photocatalytic activity in hydrogen evolution compared with pristine material. 

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Reduction of sulfur dioxide by methane is the basis of an Allied process for converting by-product sulfur dioxide to sulfur (232). The reaction is carried out in the gas phase over a catalyst. Reduction of sulfur dioxide to sulfur by carbon in the form of coal has been developed as the Resox process (233). The reduction, which is conducted at 550—800°C, appears to be promoted by the simultaneous reaction of the coal with steam. The reduction of sulfur dioxide by carbon monoxide tends to give carbonyl sulfide [463-58-1] rather than sulfur over cobalt molybdate, but special catalysts, eg, lanthanum titanate, have the abiUty to direct the reaction toward producing sulfur (234). 

Reduction with carbon monoxide at high temperatures can form either carbonyl sulfide or sulfur depending on the catalyst used. With cobalt molybdate, COS is the primary product. On the other hand, lanthanum titanate catalyzes the reaction to form sulfur. 

Rare earth containing catalysts are useful in stationary pollution control devices as for example lanthanum titanate catalysis in the reduction of sulphur dioxide with carbon monoxide to yield carbon dioxide and elemental sulphur. The disposal of elemental sulphur is far less hazardous than that of effluent from an SO2 scrubber. 

Lanthanum Oxide. La203, m.p. approx. 2200 C sp. gr. 6.51 thermal expansion (25-1000°C) 12 X 1(H. A rare earth sometimes used in special optical glasses. Lanthanum Titanates. Two compounds have been reported LaTi203 and La2Ti209 the former has a perovskite (q.v.) structure and can be synthesized by heating a mixture of La203 and Ti203 at 1200°C in a vacuum. 

Inaguma, Y. Liquan, C. Itoh, M. Nakamura, T. Uchida, T. Ikuta, H. Wakdiara, M. (1993) High Ionic Conductivity in Lithium Lanthanum Titanate. Solid State Communications, Vol. 86, No. 10, 0une 1993), pp. 689-693, ISSN 0038-1098... 

Inaguma Y et al (1993) High ionic conductivity in lithium lanthanum titanate. Solid State Commun 86(10) 689-693... 

Yang, Z., Huang, X., Yang, G., Xie, Q., Li, B., Zhou, J., and Li, L. (2009) Preparation and photonic bandgap properties of lead lanthanum titanate inverse opal photonic crystals./. Alloys Compd, 468, 295-298. 

The presence of lithium on the large interstitial site in lithium lanthanum titanate perovskites gives rise to exceptional ionic mobility. The lithium conductivity in this system can be as high as 10 S cm at room temperature, i.e. several orders of magnitude higher than many other fast lithium ion conductors. However, it must be noted that this is the value of conductivity within a crystallite and the presence of grain... 

The perovskite structure can be adjusted by the introduction of different cations to either dope the system, by using aliovalent cations, or simply by introducing cations of different sizes or polarisabilities in order to adjust the structure. In the lithium lanthanum titanate system a large number of cations can be introduced onto the A site in order to replace lanthanum or lithium l and this survey has found that the combination of lithium and lanthanum is exceptional. The similarities in the chemistry of the lanthanides are commonly exploited in structural chemistry by the substitution of one lanthanide cation with another of slightly different size. In the case of lithium lanthanum titanates this approach has a spectacular impact on the transport properties. 

Stramare S, Thangadurai V, Weppner W (2003) Lithium lanthanum titanates a review. Chem Mater 15 3974-3990... 

The aims of the addition of inert ceramic filler to the electrospun polymer fiber matrix to form polymer/ceramic composite fiber membrane for separator in LIB were on one hand to prevent dimensional changes by thermal deformation at high temperature because of the frame structure of the heat-resistant ceramic powder and on the other hand to increase the ionic conductivity of the membrane due to the intrinsic ionic conductivity of the ceramics. Various ceramic fillers had been incorporated into the electrospun polymer membranes to make composite separators, including aluminum oxide (AI2O3) [61], fumed silica (SiOa) [29,48,62], titanium dioxide (Ti02) [50, 63-65], lithium lanthanum titanate oxide (LLTO) [51], and lithium aluminum titanium phosphate (LATP) [52],... 

Liang Y, Ji L, Guo B, Lin Z, Yao Y, Li Y, Alcoutlabi M, Qiu Y, Zhang X (2011) Preparation and electrochemical characterization of iomc-conductmg litfaium lanthanum titanate oxide/polyacrylonitrile submicron composite fiber-based lithium-ion battery separators. J Power Sources 196(1) 436-441. doi 10.1016/j.jpowsour.2010.06.088... 

Liang, Y, Ji, L., Guo, B., Lin, Z., Yao, Y, Li, Y, Alcoutlabi, M., Qiu, Y, and Zhang, X., Preparation and Electrochemical Characterization of Ionic-Conducting Lithium Lanthanum Titanate Oxide/Polyaciylonitrile Submicron Composite Fiber-Based Lithium-Ion Battery Separators , Journal of Power Sources, 1%, 436-441,2011. 

Lithium lanthanum titanates, also called LLTO, are sensitive to pH of the aqueous... 

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