Transport properties of SrMoO₄/MoO₃ composites

Abstract

The work is devoted to the study of transport properties at the SrMoO₄/MoO₃ interface and examination of composite phases based on these compounds. The mass transfer in the (‒)MoO₃/SrMoO₄/MoO₃(+) cell is studied in the spontaneous mode (with no polarization) and electric field-induced mode. In the spontaneous mode, MoO₃ is drawn onto the inner surface of SrMoO₄ ceramic briquette. Under a polarization, molybdenyl ion {MoO₂}²⁺ is one of the charge carriers, which is evidenced by the Tubandt method. Thus, both spontaneously and under an external polarization, MoO₃ is transferred onto the inner surface of SrMoO₄ ceramics. It is found that the ionic transfer prevails for SrMoO₄: the average transport numbers by the emf method are close to unity, the oxygen activity in the gas phase (in the range 0.21…10^–5 atm) has no effect on the conductivity. The composites {SrMoO₄–xMoO₃} (where x = 1, 5, 10, 15, 20 mol %) are fabricated; the presence of two phases is evidenced by the X-ray diffraction analysis. The temperature dependence of the total conductivity is determined. In the range of small MoO₃ additions to SrMoO₄, the conductivity steeply increases revealing the similarity to the {MeWO₄–xWO₃ (Me–Ca, Sr, Ba)} composites.