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 800oC) 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 bms was revealed in pure La2Mo2O9 at fast cooling, which at heating turns into monoclinic a - phase near 450oC.

The stabilization of bms - 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 450-500oC.

 

Domain structure of a - phase (low temperature monoclinic)

 

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

 

 

Main publications:
  1. Voronkova V.I., Yanovskii V.K., Kharitonova E.P. Oxygen-conducting crystals of La2Mo2O9; growth and main properties // Crystallography Reports. 2005 V. 50. No. 5. P. 874-876.

  2. A. Selmi, G. Corbel, S. Kojikian, V. Voronkova, E. Kharitonova, Ph. Lacorre. Complex effect of partial substitution of La3+ by Ca2+ on the stability of fast oxide-ion conductor La2Mo2O9 // Eur. J. Inorganic Chem. 2008. V. 2008. No. 11. p. 1813-1821.

  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.

 

 

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