We report the high pressure synthesis of a layered perovskite Ca2GeO4 which is found to have the Ruddlesden–Popper structure with I41/acd symmetry. Consonant with our recent predictions [Ablitt et al., npj Comput. Mater., 2017, 3, 44], the phase displays pronounced uniaxial negative thermal expansion over a large temperature range. Negative thermal expansion that persists over a large temperature range is very unusual in the perovskite structure, and its occurrence in this instance can be understood to arise due to both soft lattice vibrations associated with a phase competition and the unusually compliant nature of this structure, which effectively couples thermal expansion in the layer plane to lattice contractions perpendicular to the layering direction via a “corkscrew” mechanism.
Negative thermal expansion in high pressure layered perovskite Ca2GeO4
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By Mark | Comments are ClosedAblitt C, Mostofi AA, Bristowe NC and Senn MS (2018) Control of Uniaxial Negative Thermal Expansion in Layered Perovskites by Tuning Layer Thickness. Front. Chem. 6:455. doi: 10.3389/fchem.2018.00455 Uniaxial negative thermal expansion (NTE) is known to occur in low $n$Read more
