Structural and transport properties of neodymium tungstates prepared via mechanochemical activation

Nd5.5WO11.25-delta, (Nd5/6La1/6)(5.5)WO11.(25)(-delta) and Nd-5.5W0.5Mo0.5O11.25-delta mixed oxides have been prepared using mechanochemical activation (MA) of Nd2O3-WO3, Nd2O3-La2O3-WO3, Nd2O3-MoO3-WO3 mixtures in a high-power planetary ball mill. Genesis of these tungstates structural properties was studied by XRD, SEM, TEM with EDX analysis, H-1 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 degrees C. Transport properties of Nd5.5WO11. 25-delta mixed oxide were improved by the partial substitution of Nd with La in (Nd5/6La1/6)(5.)5WO11.25-delta and W with Mo in Nd5.5W0.5Mo0.5O11.25-delta samples. For all samples the electrical conductivity values measured in a humid atmosphere (up to similar to 10(-3) S/cm at 550 degrees C) exceed those measured in a dry atmosphere indicating the proton character of conductivity.