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Abstract The hafnate perovskites PbHfO3(antiferroelectric) and SrHfO3(“potential” ferroelectric) are studied as epitaxial thin films on SrTiO3(001) substrates with the added opportunity of observing a morphotropic phase boundary (MPB) in the Pb1−xSrxHfO3system. The resulting (240)‐oriented PbHfO3(Pba2) films exhibited antiferroelectric switching with a saturation polarization ≈53 µC cm−2at 1.6 MV cm−1, weak‐field dielectric constant ≈186 at 298 K, and an antiferroelectric‐to‐paraelectric phase transition at ≈518 K. (002)‐oriented SrHfO3films exhibited neither ferroelectric behavior nor evidence of a polarP4mmphase . Instead, the SrHfO3films exhibited a weak‐field dielectric constant ≈25 at 298 K and no signs of a structural transition to a polar phase as a function of temperature (77–623 K) and electric field (–3 to 3 MV cm−1). While the lack of ferroelectric order in SrHfO3removes the potential for MPB, structural and property evolution of the Pb1−xSrxHfO3(0 ≤x < 1) system is explored. Strontium alloying increased the electric‐breakdown strength (EB) and decreased hysteresis loss, thus enhancing the capacitive energy storage density (Ur) and efficiency (η). The composition, Pb0.5Sr0.5HfO3produced the best combination ofEB = 5.12 ± 0.5 MV cm−1,Ur = 77 ± 5 J cm−3, and η = 97 ± 2%, well out‐performing PbHfO3and other antiferroelectric oxides.
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Harnessing Phase Transitions in Antiferroelectric ZrO 2 Using the Size Effect
Abstract The unique nonlinear dielectric properties of antiferroelectric (AFE) oxides are promising for advancements in solid state supercapacitor, actuator, and memory technologies. AFE behavior in high‐k ZrO2is of particular technological interest, but the origin of antiferroelectricity in ZrO2remains questionable. The theory of reversible electric field‐induced phase transitions between the nonpolar P42/nmc tetragonal phase and the polarPca21orthorhombic phase is experimentally tested with local structural and electromechanical characterization of AFE ZrO2thin films. Piezoresponse force microscopy identifies signature evidence of a field‐induced phase transition. A significant size effect in AFE ZrO2is experimentally observed as film thickness is scaled down from 14.7 to 4.3 nm. The size effect is explained by modifications to the phase transition energy barrier heights ranging from 0.6 to 7.6 meV f.u−1depending on crystallite size and in‐plane compressive strain with decreasing ZrO2film thickness. Using the size effect, it is possible to double the energy storage density in ZrO2from 20 J cm−3to greater than 40 J cm−3, thus highlighting a feasible route for superior performance in AFE fluorite supercapacitors.
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- Award ID(s):
- 1917635
- PAR ID:
- 10371509
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Electronic Materials
- Volume:
- 8
- Issue:
- 1
- ISSN:
- 2199-160X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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