Ionic Conductivity Enhancement of La₂Mo_2−xW_xO₉ Nanocrystalline Films Deposited on Alumina Substrates by the Sol–Gel Method

Abstract

Dense, crack-free, and uniform La 2 Mo 2Àx W x O 9 (x 5 0, 0.1, and 0.2) nanocrystalline films were successfully synthesized on poly-alumina substrates via a modified sol-gel method, with inorganic salt of La(NO 3 ) 3 . 6H 2 O, (NH 4 ) 6 Mo 7 O 24 . 4H 2 O, and (NH 4 ) 6 H 2 W 12 O 24 as precursors. Pure La 2 Mo 2 O 9 phase was confirmed by X-ray diffractometer when the annealing temperature was 45001C. The average grain size of the La 2 Mo 2Àx W x O 9 films is in the range of 90-400 nm, depending upon the conditions of thermal treatment, and the thickness of films can reach 1 lm by repetitive spin-coating. The electrical conductivity increases with decreasing grain size and reaches 0.074 S/cm at 6001C in the film with a grain size of 90 nm, which is one order of magnitude higher than that in the corresponding bulk materials. W-doping can suppress the phase transition that occurs at 5801C in pure La 2 Mo 2 O 9 and enhance the low-temperature ionic conductivity. Furthermore, the activation energy of conductivity in the nanocrystalline La 2 Mo 2 O 9 films decreases to about 0.6 eV in comparison with 1.0 eV in the bulk ones, which implies that the grain resistance prevails in the total resistance, when grain size reduces to nanometer domain. J. Stevenson-contributing editorThis work has been subsidized by the

Compositional effects on the growth of Mg(M)O films

“…A similar message to the scientific community is given by Plummer et al 2 An example of the increased complexity is the use of the complex metal oxide thin films. These coatings find application as corrosion and wear resistant coatings, 3,4 high-k dielectrics, 5,6 solid state ionic conductors in solid oxide fuel cells, [7][8][9][10] or thin film batteries. [11][12][13] As one of the future challenges for the thin film deposition, Willmott and others see the control required for the composition of complex metal oxides.…”

Conducting solids

“…The authors showed an increase in conductivity with decreasing grain size for the series La 2 Mo 2Àx W x O 9 (0 r x r 0.2). 133 The highest conductivity (0.07 S cm À1 at 600 1C) was obtained for a thin film sample with an average grain size of 90 nm.…”

Synthesis of La2Mo2O9 powders with nanodomains using polyol procedure

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