Various lithium-ion garnet-like oxides, Li 7+X-Y (La 3−X A X )(Zr 2−Y Nb Y )O 12 , (where A is an alkali earth metal) were prepared by solid-state reaction, and their lithium-ion conductivities and lattice parameters were determined by AC impedance and X-ray diffraction analysis. The La and Zr sites in these materials were simultaneously substituted, and the extent of substitution was varied to optimize both lattice parameter and lithium content associated with the highest possible lithium-ion conductivity. The optimum lattice parameter at a constant lithium content was determined to be between 12.94 and 12.96 Å. Within this range of lattice parameters, higher lithium-ion conductivities were associated with reduced lithium content.
Garnet-like oxides having the formula Li7+X−YLa3−XAXZr2−YNbYO12 (A = Sr or Ca) were synthesized using a solid-state reaction, and their bulk and grain boundary resistivities were assessed by AC impedance measurements. A difference in grain boundary resistivity was identified between Sr and Ca materials, and so the grain boundaries were examined using electron probe microanalysis (EPMA). The difference in the grain boundary resistivities was attributed to the core-shell structure of the Sr-substituted samples. In contrast, the Ca-substituted materials exhibited accumulations of impurities at the grain boundaries.
Random telegraphic noises with a preferential jump height around 0.018G(0) were observed in the conductance traces of the Au-pentacene-Au junctions. The distribution of the plateau lifetime obeyed an exponential distribution, but the decay constants were independent of the height of the adjacent conductance jumps or the measurement temperature. This result, along with the buckyferrocene (Fe(C(60)(CH(3))(5))C(5)H(5)) result, suggests that the conductance fluctuation originates from the current-induced geometrical fluctuation around a single molecule.
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