Dynamic tilting in perovskites

Handley, Christopher M.; Ward, Robyn E.; Freeman, Colin L.; Reaney, Ian M.; Sinclair, Derek C.; Harding, John H.

doi:10.1107/s2053273322011949

Cited by 8 publications

(3 citation statements)

References 37 publications

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“…Two low intensity peaks at ≈7 and ≈9° were also observed that are not modeled. These two low intensity peaks could not be identified but may represent finer‐level distortions of the perovskite structure, [34,35] as also probed below. The peak at ≈21° is overestimated by the refinement.…”

Section: Resultsmentioning

confidence: 96%

Switching Lead for Tin in PbHfO₃: Noncubic Structure of SnHfO₃**

Gabilondo,

Newell,

Broughton

et al. 2023

Angew Chem Int Ed

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The removal of lead from commercialized perovskite‐oxide‐based piezoceramics has been a recent major topic in materials research owing to legislation in many countries. In this regard, Sn(II)‐perovskite oxides have garnered keen interest due to their predicted large spontaneous electric polarizations and isoelectronic nature for substitution of Pb(II) cations. However, they have not been considered synthesizable owing to their high metastability. Herein, the perovskite lead hafnate, i.e., PbHfO3 in space group Pbam, is shown to react with SnClF at a low temperature of 300 °C, and resulting in the first complete Sn(II)‐for‐Pb(II) substitution, i.e. SnHfO3. During this topotactic transformation, a high purity and crystallinity is conserved with Pbam symmetry, as confirmed by X‐ray and electron diffraction, elemental analysis, and 119Sn Mössbauer spectroscopy. In situ diffraction shows SnHfO3 also possesses reversible phase transformations and is potentially polar between ≈130–200 °C. This so‐called ‘de‐leadification’ is thus shown to represent a highly useful strategy to fully remove lead from perovskite‐oxide‐based piezoceramics and opening the door to new explorations of polar and antipolar Sn(II)‐oxide materials.

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Section: Resultsmentioning

confidence: 96%

Switching Lead for Tin in PbHfO₃: Noncubic Structure of SnHfO₃**

Gabilondo,

Newell,

Broughton

et al. 2023

Angew Chem Int Ed

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“…So it is natural to ask, could t indicate the bond vibrational energy and thus the change of τ f ? As reported in a recent study on dynamic tilting by Handley et al., 50 the oscillation amplitudes of the oxygen octahedron tilts in CaTiO 3 increase with increasing temperature; in contrast, BaTiO 3 has a far more rigid structure. It could be speculated that when the tolerance factor of perovskites decreases, the oscillation amplitudes of the tilts would increase with temperature to a larger extent, and consequently, τ f would be closer to zero from the vibrational energy perspective or rattling effect mechanism.…”

Section: Resultsmentioning

confidence: 55%

Structure evolution and adjustment of τ_f in (Ba, Sr)HfO₃ and (Sr, Ca)HfO₃ microwave dielectric ceramics

Wang,

Zhu,

et al. 2023

J Am Ceram Soc.

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The crystal structure evaluation of Ba1‐xSrxHfO3 and Sr1‐yCayHfO3 ceramics with varying composition was determined together with its influence on microwave dielectric characteristics. The variation mechanism of temperature coefficient of resonant frequency (τf) was discussed in details, and the strong correlation between τf and bond valence sum (BVS) and tolerance factor (t) was interpreted from the view point of energy. With increasing Sr content, the stable phase of Ba1‐xSrxHfO3 at room temperature changed from Pmm (x≤0.25) to I4/mcm (0.35≤x≤0.40), then to Imma (0.50≤x<0.75) and finally to Pnma (0.75≤x≤1.0). The peak temperature of dielectric constant changed due to the structure transition, resulting in that τf rapidly declined at first, reached near zero, then slowly decreased, and finally rapidly decreased. Sr1‐yCayHfO3 (0≤y≤1.0) belonged to space group Pnma. As the bond lengths and bond angles between B‐atom and O‐atom became more and more changeable (or BVS became smaller), the crystal could store more input heat energy through bond vibrational energy, and consequenly τf became closer to zero with increasing Ca‐content, which was consistent with the physical meaning of the rattling effect on τf. With decreasing t, the dominant mechanisms responsible for tuning τf changed from (i) phase transition and (ii) dilution of ion polarizability to (iii) rattling effect. One could investigate what were the dominant mechanisms tuning τf and hopefully predict its trend with the help of τf‐t graph. These findings provided a new idea for developing solid solution ceramics with excellent temperature stability.This article is protected by copyright. All rights reserved

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“…These two low intensity peaks could not be identified but may represent fine distortions of the perovskite structure. [34,35] The peak at ~21⁰ is overestimated by fine structure. [36] The structure of PHO undergoes reversible phase changes beginning at 150 °C, then to polar phase at 180 °C, then finally to Pm3 ̅ m at 220 °C.…”

Section: III Synthesis and Stability Of Orthorhombic Snhfo3mentioning

confidence: 99%

Switching Lead for Tin in the ‘De-Leadification’ of PbHfO3: Noncubic Structure of SnHfO3

Gabilondo

Newell

Broughton

et al. 2023

Preprint

View full text Add to dashboard Cite

The removal of lead from commercialized perovskite-oxide-based piezoceramics has been a recent major topic in materials research owing to legislation in many countries. In this regard, Sn(II)-perovskite oxides have garnered keen interest due to their predicted large spontaneous electric polarizations and isoelectronic nature for substitution of Pb(II) cations. However, they have not been considered synthesizable owing to their high metastability. Herein, the perovskite lead hafnate, i.e., PbHfO3 in space group Pbam, is shown to react with SnClF at a low temperature of 300 °C, and resulting in the first complete Sn(II)-for-Pb(II) substitution, i.e. SnHfO3. During this topotactic transformation, a high purity and crystallinity is conserved with Pbam symmetry, as confirmed by X-ray and electron diffraction, elemental analysis, and 119Sn Mössbauer spectroscopy. In situ diffraction shows SnHfO3 also possesses reversible phase transformations and is potentially polar between ~130-200 °C. This so-called ‘de-leadification’ is thus shown to represent a highly useful strategy to fully remove lead from perovskite-oxide-based piezoceramics, and opening the door to new explorations of polar and antipolar Sn(II)-oxide materials.

show abstract

Dynamic tilting in perovskites

Cited by 8 publications

References 37 publications

Switching Lead for Tin in PbHfO₃: Noncubic Structure of SnHfO₃**

Switching Lead for Tin in PbHfO₃: Noncubic Structure of SnHfO₃**

Structure evolution and adjustment of τ_f in (Ba, Sr)HfO₃ and (Sr, Ca)HfO₃ microwave dielectric ceramics

Switching Lead for Tin in the ‘De-Leadification’ of PbHfO3: Noncubic Structure of SnHfO3

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Dynamic tilting in perovskites

Cited by 8 publications

References 37 publications

Switching Lead for Tin in PbHfO3: Noncubic Structure of SnHfO3**

Switching Lead for Tin in PbHfO3: Noncubic Structure of SnHfO3**

Structure evolution and adjustment of τf in (Ba, Sr)HfO3 and (Sr, Ca)HfO3 microwave dielectric ceramics

Switching Lead for Tin in the ‘De-Leadification’ of PbHfO3: Noncubic Structure of SnHfO3

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Product

Resources

About

Switching Lead for Tin in PbHfO₃: Noncubic Structure of SnHfO₃**

Switching Lead for Tin in PbHfO₃: Noncubic Structure of SnHfO₃**

Structure evolution and adjustment of τ_f in (Ba, Sr)HfO₃ and (Sr, Ca)HfO₃ microwave dielectric ceramics