Giant negative thermal expansion exceeding 1000 K in PrMnO<sub>3</sub> via synergy of local structure distortion and orbital disordering.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41233337.
- Also identified by DOI 10.1038/s41467-025-64925-7 and PMC identifier 12615802.
- Licence recorded as CC BY-NC-ND.
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Abstract
Giant negative thermal expansion (NTE), defined by volumetric expansion α<sub>V</sub> <ca. -50 × 10<sup>-6</sup> K<sup>-1</sup> (volume contraction (ΔV/V) < - 0.5% within ~100 K), is rarely observed at high temperatures. Here, we report a giant NTE persisting above 1000 K (ΔV/V = - 1.7 %, 900-1100 K) in stoichiometric PrMnO<sub>3</sub> (PMON) with a peak coefficient α<sub>V</sub> = - 114 × 10<sup>-6 </sup>K<sup>-1</sup> around 1000 K. Contrastingly, oxygen-rich PrMnO<sub>3+x</sub> (PMOA) exhibits only positive thermal expansion. The origin of NTE was uncovered via synchrotron X-ray total scattering, Cs-corrected STEM, and DFT calculations. Intriguingly, PMON uniquely hosts a local symmetry breaking featured by a 3D cross-arranged network of elongated Mn-O bonds, different from the 2D planar configurations in PMOA. By correlating atomic-scale symmetry breaking and thermally activated orbital reconfiguration to macroscopic thermal responses, we establish an unconventional paradigm for engineering giant NTE at elevated temperatures.