Revealing the role of B-site cations in the antiferroelectricity of NaNbO3-based perovskites

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The promising prospects of antiferroelectric perovskite oxides in the realm of energy storage applications hinge on the unique field-induced phase transitions. Once the transition is triggered by the application of an electric field, characteristic double polarization loops appear. However, NaNbO3-based materials that exhibit a reversible phase transition are still rare, which hinders the practical applications of lead-free antiferroelectrics. Here, the impact of materials chemistry on the competition between antiferroelectric and ferroelectric states is demonstrated in a series of NaNbO3-based solid solutions with varying perovskite B-site cations, while the A-site is fixed as strontium. The crystal structure is analyzed on the basis of Rietveld refinement of high-energy X-ray diffraction data. The phase transition behavior as well as the antiferroelectric and ferroelectric properties are probed by a series of electrical measurements. The antiferroelectric phase is universally observed for all investigated materials in the virgin state. The SrTiO3-substituted system shows an irreversible phase transition similar to that of pure NaNbO3. In contrast, double polarization hysteresis loops are observed in the SrHfO3-, SrZrO3-, and SrSnO3-substituted systems. It is confirmed that compounds that can reduce the tolerance factor of the system contribute to the stabilization of the antiferroelectric order, while those that can reduce the electronegativity difference lead to more pronounced double loops. The competition between antiferroelectricity and ferroelectricity is linked to the competition between covalent and ionic bonding in perovskites.