Synthesis, sinterability, conductivity and reducibility of K+ and W6Â + double doped La2Mo2O9

La2−xKxMoWO9−δ (x = 0, 0.01, 0.03, 0.05, 0.07) was synthesized via a solid state reaction method. The results of X-ray diffraction studies show that after calcination at 800°°C the precursor powder primarily forms a mixture of β-La2Mo2O9 and La6W2O15 phases. Single β-La2Mo2O9 phase is obtained after calcination at 950°C, and the solid solubility limit of K+ doping is x < 0.07. The particle size distribution of samples indicates that when x = 0.03 the powder has the largest average particle size and agglomeration exists. The sintering behavior measured by a dilatometer reveals the decrease of sintering temperature with increasing K+ content. Electrochemical impedance spectroscopy in air and 5% H2/Ar mixed gas demonstrates the conductivity of La1.97K0.03MoWO9−δ is twice higher than that of La2MoWO9 at 800°C. The reducibility is also enhanced by K+ and W6 + double doping.