Electrical Conductivity of Mullite Ceramics

Abstract

The electrical conductivity of a lab‐produced homogeneous mullite ceramic sintered at 1625°C for 10 h with low porosity was measured by impedance spectroscopy in the 0.01 Hz to 1MHz frequency range at temperatures between 300°C and 1400°C in air. The electrical conductivity of the mullite ceramic is low at 300°C (≈0.5 × 10−9 Scm−1), typical for a ceramic insulator. Up to ≈ 800°C, the conductivity only slightly increases (≈0.5 × 10−6 Scm−1 at 800°C) corresponding to a relatively low activation energy (0.68eV) of the process. Above ≈ 800°C, the temperature‐dependent increase in the electrical conductivity is higher (≈10−5 Scm−1 at 1400°C), which goes along with a higher activation energy (1.14 eV). The electrical conductivity of the mullite ceramic and its temperature‐dependence are compared with prior studies. The conductivity of polycrystalline mullite is found to lie in‐between those of the strong insulator α‐alumina and the excellent ion conductor Y‐doped zirconia. The electrical conductivity of the mullite ceramic in the low‐temperature field (< ≈800°C) is approximately one order of magnitude higher than that of the mullite single crystals. This difference is essentially attributed to electronic grain‐boundary conductivity in the polycrystalline ceramic material. The electronic grain‐boundary conductivity may be triggered by defects at grain boundaries. At high temperatures, above ≈ 800°C, and up to 1400°C gradually increasing ionic oxygen conductivity dominates.

Investigation on magnetic and electric properties of morphologically different perovskite LaFeO3 nanostructures

“…4a, the complex Cole-Cole (or Nyquist) plot [-Im(Z) vs. Re(Z)] consists of a well resolved semicircle whose center is located below the real axes, i.e., a non Debye behavior, and a spike at low frequencies for a selected ceramic of LaFeO 3 nanopetals at room temperature. The spike is an evidence of the electrode polarization effect during our measurements [38]. Besides, these behaviors were found for all LaFeO 3 ceramics with different morphologies.…”

Microstructure and properties of the mullite‒ZrO₂(Y₂O₃)‒Si₃N₄-composite ceramics sintered in different ways

“…ВВЕДЕНИЕ И звестно [1], что муллитосодержащая керамика широко применяется в высокотемпературных процессах, в которых необходимо сохранение ее высоких термомеханических свойств. Ряд специфических свойств этой керамики -устойчивость к температурным перепадам, агрессивным химическим средам, в некоторых случаях электрическим характеристикам -улучшают модифицированием состава керамики, чаще всего ZrO 2 (или ZrSiO 4 ), оксидaми магния, лантана [2,3].…”

A comparative electrical study of nano-crystalline mullite with low dielectric loss due to incorporation of tungsten and molybdenum ion: their uses in electronic industries

“…This is in spite of the suggested onset of hopping of oxygen atoms bridging the tetrahedral double chains in mullite toward the oxygen vacancies at high temperature. Possible explanations are complex structural rearrangements going along with the oxygen hopping in mullite due to metal ion contain [46,48]. Higher electrical conductivities may be achieved by controlled grain-boundary conductivity.…”