Pressure- and temperature-induced transformation processes in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>PbTiO</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:mtext>−</mml:mtext> <mml:msub> <mml:mrow> <mml:mi>Bi</mml:mi> <mml:mi>M</mml:mi> <mml:mi>e</mml:mi> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> </mml:msub> </mml:mrow> </mml:math> ferroelectrics
Bibliographic record
Abstract
The structural response to high pressures as well as to high temperatures of $(1\text{\ensuremath{-}}x){\mathrm{PbTiO}}_{3}\text{\ensuremath{-}}x\mathrm{Bi}({\mathrm{Zn}}_{0.5}{\mathrm{Ti}}_{0.5}){\mathrm{O}}_{3}$ with $x=0.08$, $(1\text{\ensuremath{-}}x){\mathrm{PbTiO}}_{3}\text{\ensuremath{-}}x\mathrm{Bi}({\mathrm{Mg}}_{0.5}{\mathrm{Ti}}_{0.5}){\mathrm{O}}_{3}$ with $x=0.17$, and ${\mathrm{PbTiO}}_{3}$ single crystals was studied by in situ pressure-/temperature-dependent polarized Raman spectroscopy, complemented by synchrotron x-ray diffraction analysis at ambient pressure and different temperatures. The compositional and pressure dependencies of phonon anomalies indicate the existence of local-scale antiferrodistortive structural entities inside the perovskite $({\mathrm{ABO}}_{3})$ polar tetragonal matrix, the fraction of which is enhanced by the substitution of ${\mathrm{Bi}Me\mathrm{O}}_{3}$ for ${\mathrm{PbTiO}}_{3}$. The type of cation (${\mathrm{Zn}}^{2+}$ versus ${\mathrm{Mg}}^{2+}$) replacing ${\mathrm{Ti}}^{4+}$ at the B site affects the coherence within the dominant single-perovskite polar tetragonal matrix and the coupling between the ``defect'' double-perovskite antiferrodistortive entities. As a result, on increasing pressure, the partial substitution of $\mathrm{Bi}({\mathrm{Mg}}_{0.5}{\mathrm{Ti}}_{0.5}){\mathrm{O}}_{3}$ triggers a structural instability at lower pressure values as compared to pure ${\mathrm{PbTiO}}_{3}$, whereas that of $\mathrm{Bi}({\mathrm{Zn}}_{0.5}{\mathrm{Ti}}_{0.5}){\mathrm{O}}_{3}$ preserves the polar tetragonal phase over a wider pressure range. Furthermore, at ambient pressure B-site ${\mathrm{Zn}}^{2+}$ favors the coherence between local ${\mathrm{BO}}_{6}$ tetragonal distortions already above the Curie temperature ${T}_{C}$, causing a larger unit-cell tetragonality below ${T}_{C}$; in contrast, B-site ${\mathrm{Mg}}^{2+}$ reduces the local ${\mathrm{BO}}_{6}$ anisotropy and disturbs the correlation between polar ${\mathrm{AO}}_{12}$ tetragonal distortions below ${T}_{C}$, which results in a considerable reduction of both the unit-cell tetragonality and accumulated volume strain on cooling between ${T}_{C}$ and room temperature.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.054 | 0.007 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".