Structural and transport properties of mechanochemically synthesized La_(0.9)Ba_(0.1)F_(2.9) and La_(0.9)Ba_(0.05)Ca_(0.05)F_(2.9)

摘要

LaF3 based fast ion conducting materials are well-known potential solid electrolytes for applications in different solid-state ionic devices like fluoride ion batteries. LaF3 of crystallite size in the nanometer range is obtained by mechanical milling the as procured LaF3 for a few hours. The mechanically milled LaF3 shows higher conductivity in comparison to its un-milled forms. The enhanced conductivity value exhibited by the mechanically milled LaF3 is explained with respect to its smaller crystallite size and induced micro-strain during the milling process. The influence of bivalent dopant, BaF2 (fluorite structure) on LaF3 (tysonite structure) has been studied using XRD and impedance spectroscopy techniques. La0.9Ba0.1F2.9 shows higher conductivity in comparison to LaF3 conductivity and the observed result is explained with respect to the differences in the ionic radii and valence state of the dopant Ba2+ and the host La3+ ions. Furthermore, the role of the co-dopant CaF2 on the structural and transport properties of BaF2 doped LaF3 keeping same La and F stoichiometry as in La0.9Ba0.1F2.9 is investigated. The transport results indicate a lower conductivity value in La0.9Ba0.05Ca0.05F2.9 in comparison to La0.9Ba0.1F2.9 conductivity.