Tunable Negative Thermal Expansion in Layered Perovskites from Quasi-Two-Dimensional Vibrations

Huang, Liang‐Feng; Lu, Xiaochen; Rondinelli, James M.

doi:10.1103/physrevlett.117.115901

Cited by 33 publications

(37 citation statements)

References 44 publications

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“…For this reason, we repeated a sequential process of including the condensation of identified unstable modes, structural optimization, and phonon calculations up to the point where no unstable mode remained in the structure to find the lowest‐energy polymorphs. As shown in Table 3 and Figure S8 (Supporting Information), the systematic stable‐structure exploration reveals the polar A 2 1 am phase to be the most stable, consistent with our experimental observation and previous first‐principles investigation, and it also uncovers many possible metastable phases. We next calculated the energy surface around the aristotype I 4/ mmm phase using DFT to identify the role of the OOR and OOT modes in stabilizing the ground‐state A 2 1 am phase.…”

Section: Resultssupporting

confidence: 88%

“…The RP phases of general formula A O( AB O 3 ) n (or A n +1 B n O 3 n +1 ) have a layered structure where n AB O 3 perovskite blocks are stacked along the [001] direction, with an extra A O rock salt layer inserted for every n perovskite units (see Figure for n = 2) . Although n = 2 RP Sr 3 Zr 2 O 7 was previously reported to adopt a centrosymmetric Pmmm symmetry, recent theoretical work and first‐principles calculations indicated that Sr 3 Zr 2 O 7 is a potential HIF with A 2 1 am symmetry . We first characterized the room‐temperature crystal structure of Sr 3 Zr 2 O 7 using SXRD and NPD.…”

Section: Resultsmentioning

confidence: 99%

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Ferroelectric Sr₃Zr₂O₇: Competition between Hybrid Improper Ferroelectric and Antiferroelectric Mechanisms

Yoshida

Fujita

Akamatsu

et al. 2018

Adv Funct Materials

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In contrast to polar cation displacements driving oxides into noncentrosymmetric and ferroelectric states, inversion-preserving anion displacements, such as rotations or tilts of oxygen octahedra about cation coordination centers, are exceedingly common. More than one nonpolar rotational mode in layered perovskites can lift inversion symmetry and combine to induce an electric polarization through a hybrid improper ferroelectric (HIF) mechanism. This form of ferroelectricity expands the compositional palette to new ferroelectric oxides because its activity derives from geometric rather than electronic origins. Here, the new Ruddlesden-Popper HIF Sr 3 Zr 2 O 7 , which is the first ternary lead-free zirconate ferroelectric, is reported and room-temperature polarization switching is demonstrated. This compound undergoes a first-order ferroelectric-to-paraelectric transition, involving an unusual change in the "sense" of octahedral rotation while the octahedral tilt remains unchanged. Our experimental and first-principles study shows that the paraelectric polymorph competes with the polar phase and emerges from a trilinear coupling of rotation and tilt modes interacting with an antipolar mode. This form of hybrid improper "antiferroelectricity" is recently predicted theoretically but has remained undetected. This work establishes the importance of understanding anharmonic interactions among lattice degrees of freedom, which is important for the discovery of new ferroelectrics and likely to influence the design of next-generation thermoelectrics.

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Ferroelectric Sr₃Zr₂O₇: Competition between Hybrid Improper Ferroelectric and Antiferroelectric Mechanisms

Yoshida

Fujita

Akamatsu

et al. 2018

Adv Funct Materials

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“…We find that Ca 3 Ge 2 O 7 possesses a similarly compliant eigenvector to Ca 2 GeO 4 when compared to its parent I4/mmm structure. It should be noted that the unrelated ferroelectric Cmc2 1 phase of Ca 3 Ti 2 O 7 has also been predicted to show NTE when under sufficient pressure, 25 but is beyond the scope of the current study. Considering two more layered perovskite families with related uniaxial NTE: the tetragonal I4/m phase of the double perovskite Sr 2 MgWO 6 (NTE along the c axis between 15-300 K 26 ) and the orthorhombic Cmc2 1 phase of LaTaO 4 , belonging to the n = 2 member of the A n B n O 3n+2 family, (NTE along the b axis normal to the layering 373-573 K 27 ), we again find more compliant s H eigenvalues as compared to higher symmetry parent phases of the same structure, Fm3m Sr 2 MgWO 6 and Cmcm LaTaO 4 , respectively.…”

Section: Our Calculationsmentioning

confidence: 98%

The origin of uniaxial negative thermal expansion in layered perovskites

et al. 2017

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Why is it that ABO 3 perovskites generally do not exhibit negative thermal expansion (NTE) over a wide temperature range, whereas layered perovskites of the same chemical family often do? It is generally accepted that there are two key ingredients that determine the extent of NTE: the presence of soft phonon modes that drive contraction (have negative Grüneisen parameters); and anisotropic elastic compliance that predisposes the material to the deformations required for NTE along a specific axis. This difference in thermal expansion properties is surprising since both ABO 3 and layered perovskites often possess these ingredients in equal measure in their high-symmetry phases. Using first principles calculations and symmetry analysis, we show that in layered perovskites there is a significant enhancement of elastic anisotropy due to symmetry breaking that results from the combined effect of layering and condensed rotations of oxygen octahedra. This feature, unique to layered perovskites of certain symmetry, is what allows uniaxial NTE to persist over a large temperature range. This fundamental insight means that symmetry and the elastic tensor can be used as descriptors in high-throughput screening and to direct materials design.

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“…The first two of these correspond to rigid-unit modes (RUMs) 36 —i.e., phonon modes which propagate without deforming BX 6 coordination geometries 37 , 38 . The larger number of RUMs in molecular perovskites is conceptually related to the additional flexibility driven by reduced connectivity in Ruddlesden–Popper phases 39 . By contrast, the presence of multipolar degrees of freedom reflects reorientations of non-spherical molecular A-site cations 34 , 35 , 40 .…”

Section: Introductionmentioning

confidence: 99%

Recipes for improper ferroelectricity in molecular perovskites

2018

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The central goal of crystal engineering is to control material function via rational design of structure. A particularly successful realisation of this paradigm is hybrid improper ferroelectricity in layered perovskite materials, where layering and cooperative octahedral tilts combine to break inversion symmetry. However, in the parent family of inorganic ABX3 perovskites, symmetry prevents hybrid coupling to polar distortions. Here, we use group-theoretical analysis to uncover a profound enhancement of the number of improper ferroelectric coupling schemes available to molecular perovskites. This enhancement arises because molecular substitution diversifies the range of distortions possible. Not only do our insights rationalise the emergence of polarisation in previously studied materials, but we identify the fundamental importance of molecular degrees of freedom that are straightforwardly controlled from a synthetic viewpoint. We envisage that the crystal design principles we develop here will enable targeted synthesis of a large family of new acentric functional materials.

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Tunable Negative Thermal Expansion in Layered Perovskites from Quasi-Two-Dimensional Vibrations

Cited by 33 publications

References 44 publications

Ferroelectric Sr₃Zr₂O₇: Competition between Hybrid Improper Ferroelectric and Antiferroelectric Mechanisms

Ferroelectric Sr₃Zr₂O₇: Competition between Hybrid Improper Ferroelectric and Antiferroelectric Mechanisms

The origin of uniaxial negative thermal expansion in layered perovskites

Recipes for improper ferroelectricity in molecular perovskites

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Tunable Negative Thermal Expansion in Layered Perovskites from Quasi-Two-Dimensional Vibrations

Cited by 33 publications

References 44 publications

Ferroelectric Sr3Zr2O7: Competition between Hybrid Improper Ferroelectric and Antiferroelectric Mechanisms

Ferroelectric Sr3Zr2O7: Competition between Hybrid Improper Ferroelectric and Antiferroelectric Mechanisms

The origin of uniaxial negative thermal expansion in layered perovskites

Recipes for improper ferroelectricity in molecular perovskites

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Product

Resources

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Ferroelectric Sr₃Zr₂O₇: Competition between Hybrid Improper Ferroelectric and Antiferroelectric Mechanisms

Ferroelectric Sr₃Zr₂O₇: Competition between Hybrid Improper Ferroelectric and Antiferroelectric Mechanisms