Impedance and electron diffraction studies on single crystals of BINIVOX |
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Authors: | P Kurek P Pongratz G Fafilek |
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Institution: | (1) Institute of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw, Poland;(2) Institute of Applied and Technical Physics, Vienna University of Technology, Wiedner Haupstr. 8-10, 1040 Vienna, Austria;(3) Institute of Technical Electrochemistry, Vienna University of Technology, Getreidemarkt 9, 1060 Vienna, Austria |
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Abstract: | Single crystals of the nominal composition Bi2V0.9Ni0.1O5.35 were prepared. They were studied by TGA/DTA, impedance spectroscopy and electron diffraction. The impedance of the crystals
with Pt electrodes was measured in two directions: parallel and perpendicular to the layers of the intergrowth structure in
the frequency range 10−2−107 Hz at temperatures between 300 and 940 K. Arrhenius type plots for both directions show two linear regions with different
activation energies. In the low temperature region the conductivity in the direction parallel to the layers was by a factor
of about 1000 larger than in the perpendicular direction. In the high temperature region the ratio of conductivities was about
100. A time dependence of the conductivity in the perpendicular direction was observed during heating and cooling in limited
temperature ranges. The electron diffraction experiments gave evidence that the superlattice spots present in the diffraction
patterns at low temperature, disappear reversibly at temperatures higher than 650 K. The transition temperatures observed
in the DTA and in the electron diffraction experiments correspond to the temperature of changes of the activation energy.
An order-disorder transition of oxygen ions is considered to be responsible for this phenomenon.
Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998. |
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