Optimizing the synthesis route of trilayer nickelate: La4Ni3O10 in polycrystalline form

In the recent years, layered Nickelates are extensively studied in search of exotic quantum phases – low dimensional magnetism, charge density wave (CDW) and high temperature superconductivity (HTSC). La4Ni3O10 is one of the layered Nickelate in Ruddlesden-Popper series which shows a metal to insulator to metal (MIM) transition, characteristic of CDW formation. Often these kinds of MIM transitions are extremely sensitive to synthesis conditions. In this article, we have reported an optimized synthesis method for La4Ni3O10 which shows the MIM transition. Conventional solid state synthesis method proved to be ineffective for the synthesis of polycrystalline La4Ni3O10. Single phase polycrystalline samples of La4Ni3O10 were obtained from the citric acid method by a series of post annealing at higher temperatures. The stability of the synthesized La4Ni3O10 was studied up to highest temperature of 1250 oC. Powder X-ray diffraction, Energy Dispersive Spectroscopy and Raman measurements of the annealed samples were carried out to establish phase stability. The phase pure La4Ni3O10 shows MIM transition below 140 K. The study shows how the annealing temperature affects the formation of single phase La4Ni3O10, synthesized through citric acid method.