Another significant discovery has been made in the currently very popular and rapidly evolving field of Ruddlesden-Popper Nickelates. Scientists at Argonne National Laboratory have discovered a new polymorph of the RP phase La₃Ni₂O₇. Boules of this polymorph, which were grown under high oxygen pressure with a ScIDre optical floating zone furnace HKZ-150 at 13 to 16 bar, were analyzed using single-crystal X-ray diffraction and transmission electron microscopy. It turned out that the newly discovered polymorph had a novel stacking sequence of alternating n = 1 and n = 3 perovskite slab layers in an ordered RP oxide phase. This deviating stacking affects the electrical transport behaviour of the compound. Transport measurements at ambient pressure revealed metallic character with evidence of a charge density wave transition.

https://pubs.acs.org/doi/10.1021/jacs.3c14052