Structural and transport properties of neodymium tungstates prepared via mechanochemical activation

Abstract

Abstract Nd 5.5 WO 11.25- δ , (Nd 5/6 La 1/6 ) 5.5 WO 11.25- δ and Nd 5.5 W 0.5 Mo 0.5 O 11.25- δ mixed oxides have been prepared using mechanochemical activation (MA) of Nd 2 O 3 -WO 3 , Nd 2 O 3 -La 2 O 3 -WO 3 , Nd 2 O 3 -MoO 3 -WO 3 mixtures in a high-power planetary ball mill. Genesis of these tungstates structural properties was studied by XRD, SEM, TEM with EDX analysis, 1 H NMR, IR and Raman spectroscopy. X-ray diffraction has revealed that MA results in formation of a pure fluorite structure already after milling. High-density ceramic pellets have been obtained after sintering at 1350\u202f°C. Transport properties of Nd 5.5 WO 11.25- δ mixed oxide were improved by the partial substitution of Nd with La in (Nd 5/6 La 1/6 ) 5.5 WO 11.25- δ and W with Mo in Nd 5.5 W 0.5 Mo 0.5 O 11.25- δ samples. For all samples the electrical conductivity values measured in a humid atmosphere (up to ~ 10 −3 S/cm at 550\u202f°C) exceed those measured in a dry atmosphere indicating the proton character of conductivity.