Incipient ferroelectricity in methylammonium lead halide perovskites
Bibliographic record
Abstract
Lead halide perovskites are promising materials for optoelectronic applications. Ferroelectricity is often considered as a phenomenon that improves their properties. However, the very existence of ferroelectricity in these materials is still debatable. Here we investigate the dielectric and ferroelectric properties of the single crystals of organic-inorganic hybrid CH3NH3PbX3 (X = I, Br or Cl) and all-inorganic CsPbBr3 perovskites, which are among the most technologically useful materials. We find that MAPbX3 perovskites are incipient ferroelectrics of the order-disorder type and provide experimental evidence. We show that in contrast to SrTiO3 and other known displacive-type incipient ferroelectrics, where the ferroelectric phase is suppressed by low-temperature quantum fluctuations, in the hybrid halide perovskites the order-disorder ferroelectric transition is not attained upon cooling because the first-order octahedral tilting transition to the antiferrodistortive orthorhombic phase occurs at a temperature higher than the expected ferroelectric Curie temperature. The tilting of corner-sharing PbX6 octahedra prevents the ferroelectric ordering of MA dipoles. This insight expands our understanding of the fundamental properties of halide perovskites and suggests strategies for designing ferroelectric organic-inorganic materials. It is widely debated if ferroelectricity exists in lead halide perovskites. Here, the dielectric and ferroelectric properties of CH3NH3PbX3 and CsPbBr3 perovskite single crystals are studied, showing evidence that MAPbX3 perovskites are incipient ferroelectrics of order-disorder type.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".