Grain-size-induced ferroelectricity in NaNbO3

Jurij Koruza*, Pedro Groszewicz, Hergen Breitzke, Gerd Buntkowsky, Tadej Rojac, Barbara Malič

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The influence of a material's length scale on its functional properties has been reported for many ferroics, where a decrease in the dielectric, ferroelectric, and piezoelectric properties is frequently observed when the size is reduced below the micrometer range. Here we demonstrate that in NaNbO3, in contrast to general expectations, a long-range ferroelectric order is induced when decreasing the size. A series of sintered, polycrystalline, NaNbO3 samples with different grain sizes was prepared and analyzed using differential scanning calorimetry, dielectric measurements, and 23Na 3QMAS nuclear magnetic resonance (NMR). A size-induced phase transition into the ferroelectric polymorph was observed when the grain size decreased below 0.27 μm. The different polymorphs were distinguished based on the local symmetry of the Na(1) sodium site. NMR was also used to determine the relative amounts of the polymorphs in the samples. The observed size-induced phase transition is attributed to the existence of intragranular stresses, induced by the decreased compensation of the ferroelastic energy during the formation of non-180° domain walls when decreasing the grain size and the large anisotropy of the thermal expansion. The results demonstrate the unique possibility of stabilizing ferroelectricity by reducing the grain size, which was not observed in other ferroic systems.

Original languageEnglish
Pages (from-to)77-85
Number of pages9
JournalActa Materialia
Publication statusPublished - 1 Mar 2017


  • Antiferroelectrics
  • Ferroelectrics
  • Ferroics
  • NMR
  • Phase transitions

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys


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