Conductivity of composite materials based on Me2(WO4)3 and WO3 (Me = Sc, In)

• Published in: Russian journal of electrochemistry 2014, Vol.50 (1), p.58-69
• Main Authors: Neiman, A. Ya, Karapetyan, A. V., Pestereva, N. N.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Electrochemistry; Physical Chemistry
• ISSN: 1023-1935; 1608-3342
• DOI: 10.1134/S1023193512110122

Composites {Me 2 (WO 4 ) 3 − x WO 3 } (Me = Sc, In) ( x = 0.5–99%) are synthesized and characterized by XRD and electron microscopy methods and also by the density and specific surface measurements. Temperature dependences of the total conductivity of composites are measured. The contributions of σ tot and σ el are assessed by the and EMF methods. The concentration dependences of conductivity and activation energy are plotted based on the σ tot and σ ion data. It is shown that (a) in the interval x = 0–30 vol % WO 3 (0–70 mol %), the conductivity is independent of composition and the ionic component prevails; (b) in the interval x = 60–94.5 vol % (90–99 mol %), the electron conductivity prevails and increases with the increase in x ; (c) in the x interval of 30–60 vol % WO 3 (70–90 mol %), the conductivity is mixed, i.e., electron( n -type)-ionic; the latter region represents the transition interval from ionic to electron conductivity as x increases. These data are compared with the results obtained earlier for MeWO 4 -WO 3 composites (Me = Ca, Sr, Ba). As regards the structural topology, the {Me 2 (WO 4 ) 3 − x WO 3 } composites pertain to the randomly distributed type. It is shown that in contrast to {Me II WO 4 · x WO 3 } composites, the composites under study do not form the nonautonomous interface phase with the high ionic conductivity. The possible reasons for the observed differences in the topology and the conduction type of composites based on MeWO 4 and Me 2 (WO 4 ) 3 are analyzed.