Electrical properties of murataite modules with complex and large-volume fluorite-type superstructures

• Well-crystalized complex oxide with 3 × 3 × 3 and 8 × 8 × 8 fluorite-type superstructures are successfully synthesized.
• The electrical properties of murataite modules, 3 × 3 × 3 and 8 × 8 × 8 fluorite-type superstructures, are first presented.
• Discussing for a potential application of these murataite ceramics.

We have synthesized murataite modules with oxygen-deficient fluorite-type superstructures by a solid-state reaction method and investigated their electrical properties. The multiples of the fluorite-type unit-cell were determined using X-ray diffraction (XRD) and transmission electron microscope-selected area electron diffraction (TEM-SAED). They revealed that well-crystalized 3 × 3 × 3 (M3) and 8 × 8 × 8 (M8) fluorite-type superstructures were successfully synthesized with minor impurities. The calculated lattice constants of the M3 and M8 were 1.4589 and 3.9269 nm, respectively. Based on four-probe D.C. method and two-probe A.C impedance spectroscopy measurement, the electrical conductivity was measured as functions of temperature and oxygen partial pressure. The electrical conductivities of murataite modules increased with elevating temperature, which indicated typical semiconducting behavior. Impedance spectra suggested that either electronic or hole conduction must be superior to the ionic conduction in M3 phase. The M3 phase demonstrated good thermal stability under oxidizing and reducing atmosphere at 573–973 K.

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