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Genesis of Al-doped apatite-type nanocrystalline lanthanum silicates prepared by mechanochemical synthesis: Phase, structural and microstructural study

Tamara Kharlamova 1Svetlana Pavlova 1Vladislav A. Sadykov 1Marina Chaikina 2Tamara Kriger 1Olga Lapina 1Dzhalil Khabibulin 1Arcady Ishchenco 1Vladimir Zaikovskii 1

1. Boreskov Institute of Catalysis (BIC), pr. akad. Lavrentieva, 5, Novosibirsk 630090, Russian Federation
2. Institute for Solid State and Mechanical Chemistry of RAS, Novosibirsk 630090, Russian Federation


Apatite-type lanthanum silicates (ATLS), especially doped ones, have recently attracted a considerable attention due to their high ionic conductivity at intermediate temperatures but their usual synthesis requires too long firing cycles at ~1500°C. To promote ATLS application, the development of low-temperature preparation methods is necessary. Earlier, mechanochemical treatment has been successfully used for a low-temperature synthesis of undoped ATLS.

In this work, the results on the formation of Al-doped ATLS in the course of mechanochemical activation (MA) in a high-power planetary ball mill at room temperature are presented. Phase and structure evolution during 5-35 min MA of a stoichiometric mixture containing La2O3, Al(OH)3 and amorphous SiO2 were investigated using XRD, IR, NMR and TEM methods. At the first MA stage, a strong structure disorder of the initial La2O3 and SiO2 occurs with a formation of an amorphous aluminosilicate phase as a result of interaction of SiO2 and Al(OH)3 and, at the same time, an apatite phase starts to form. At increasing MA time, further interaction of highly disordered La2O3 and amorphous aluminum silicate which cover La2O3 particles suggests the formation of highly crystalline ATLS with a particle size of 10-60 nm. Subsequent MA of formed ATLS leads to distortion of ATLS anion sublattice and to destruction of some share of ATLS resulted in the formation of LaAlO3. The latter fact shows a restriction of Al-substitution on Si-sites into ATLS.


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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium A, by Tamara Kharlamova
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-13 14:14
Revised:   2009-06-07 00:44