A FAMILY OF OXIDE-ION CONDUCTORS ON THE BASE OF La₂Mo₂O₉

Single crystals of the pure La₂Mo₂O₉

Oxide ion conductors of LAMOX family with parent compound La₂Mo₂O₉ have the conductivity (at 800^oC) on the order as yttrium and calcium stabilized ZrO₂.

For the first time La₂Mo₂O₉ single crystals were obtained from non-stoichiometric melt in the system La₂O₃-MoO₃ and their polymorphysm, domain structure and temperature dependencies of conductivity and dielectric permittivity were studied in the pure La₂Mo₂O₉ and doped with V, Bi, Na, K, Rb, Cs, Ba, Sb, Mg, Zn, Lu, Tm, Yb, W compounds by calorimetric and electrophysical methods.

A metastable cubic phase b_ms was revealed in pure La₂Mo₂O₉ at fast cooling, which at heating turns into monoclinic a - phase near 450^oC.

The stabilization of b_ms - phase takes place at room temperature under doping with some dopants including Bi, W and V. Depending on doping level it turns into monoclinic a - phase or in high temperature most conductive cubic b - phase near 450-500^oC.

Domain structure of a - phase (low temperature monoclinic)

Sketch of LM phase transformations obtained with single crystals by polarization microscopy

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3. V.I. Voronkova, E.P. Kharitonova, A.E. Krasilnikova, N.N. Kononkova. Phase transition peculiarities in LAMOX single crystals // J. Phys.: Condens. Matter. 2008. V. 20. No. 14. p. 195210-1 – 195210-5.

4. V.I. Voronkova, E.P. Kharitonova, A.E. Krasilnikova. Phase transitions and electrical conductivity of Bi-doped La₂Mo₂O₉ oxide ion conductors // Phys. Status Solidi A. 2009. in press.

5. V.I. Voronkova, E.P. Kharitonova, A.E. Krasilnikova. Phase transition and conductivity peculiarities of oxide-ion conductive La₂Mo₂O₉ compound doped with vanadium // Crystallography Reports. 2009. in press.