Gas-tight proton-conducting Nd2 − xCa xZr2O7 − δ (x = 0, 0.05) ceramics

A. V. Shlyakhtina, N. V. Lyskov, E. Yu Konysheva, S. A. Chernyak, I. V. Kolbanev, G. A. Vorobieva, L. G. Shcherbakova

Research output: Journal PublicationArticlepeer-review

5 Citations (Scopus)

Abstract

Gas-tight Nd2 − xCaxZr2O7 − δ (x = 0, 0.05) pyrochlore materials have been prepared via mechanical activation of Nd2O3, ZrO2, and CaO, followed by single-step sintering of green compacts at 1600 °C for 3 or 10 h. Their structure has been studied using Rietveld refinement of X-ray diffraction data; their microstructure has been examined by scanning electron microscopy, and their conductivity has been determined by impedance spectroscopy in dry and wet air. In addition, we have assessed the effect of prolonged hydration on the proton conductivity of the Nd2 − xCaxZr2O7 − δ (x = 0, 0.05) pyrochlores. According to the Rietveld refinement results, Ca cations are incorporated into both Nd- and Zr- sub-lattice in Nd2 − xCaxZr2O7 − δ (x = 0.05) synthesized at 1600 °C, and most of the Ca cations reside on the Zr sites. The 500 °C proton conductivity of Nd2Zr2O7 is 5 × 10−6 S/cm (~ 1 × 10−5 S/cm at 600 °C) and that of Nd2 − xCaxZr2O7 − δ (x = 0.05) is 7 × 10−5 S/cm (~ 2.5 × 10−4 S/cm at 600 °C). Prolonged (5 months) immersion in water at room temperature has been shown to reduce the proton conductivity of Nd2 − xCaxZr2O7 − δ (x = 0, 0.05), which is attributable to partial dissolution of Nd and Ca. CaO and, to a considerably lesser extent, Nd2O3 segregation on polished and thermally etched (1450 °C) sections of the ceramics has been demonstrated. We attribute both effects to the high diffusion mobility of Ca2+ and Nd3+ cations, due to the basicity of their oxides in ambient air and water.

Original languageEnglish
Pages (from-to)1475-1486
Number of pages12
JournalJournal of Solid State Electrochemistry
Volume24
Issue number7
DOIs
Publication statusPublished - 1 Jul 2020

Keywords

  • Anti-site cation disorder
  • Ca doping
  • NdO segregation
  • NdZrO
  • Proton conductivity
  • Pyrochlore

ASJC Scopus subject areas

  • Materials Science (all)
  • Condensed Matter Physics
  • Electrochemistry
  • Electrical and Electronic Engineering

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