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Grain-size-induced ferroelectricity in NaNbO3

Koruza, Jurij and Groszewicz, Pedro B. and Breitzke, H. and Buntkowsky, G. and Rojac, Tadej and Malič, Barbara (2017):
Grain-size-induced ferroelectricity in NaNbO3.
In: Acta Materialia, Elsevier, pp. 77-85, (126), [Article]

Abstract

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 mm. 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° domainwalls 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.

Item Type: Article
Erschienen: 2017
Creators: Koruza, Jurij and Groszewicz, Pedro B. and Breitzke, H. and Buntkowsky, G. and Rojac, Tadej and Malič, Barbara
Title: Grain-size-induced ferroelectricity in NaNbO3
Language: English
Abstract:

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 mm. 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° domainwalls 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.

Journal or Publication Title: Acta Materialia
Number: 126
Publisher: Elsevier
Uncontrolled Keywords: Ferroics Phase transitions NMR Ferroelectrics Antiferroelectrics
Divisions: 11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Nonmetallic-Inorganic Materials
11 Department of Materials and Earth Sciences
Date Deposited: 03 Jan 2017 07:13
Identification Number: doi:10.1016/j.actamat.2016.12.049
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