Growth and Oxygen Stoichiometry Control of High-Quality La₂CoO_4+δ Single Crystals (δ = 0.25)

Abstract

La2CoO4+ is a strongly correlated oxide with exciting physical and electronic properties originating from the subtle interplay of lattice, orbital, charge, and spin degrees of freedom. In particular, the oxygen rich La2CoO4.25 is a key compound for studying oxygen and electronic ordering phenomena and their correlation. Single crystal growth of these phases has been plagued by difficulties related to its incongruent melting. In this work, we report on the 2 growth and characterization of high quality, centimeter sized La2CoO4.25 single crystals, suitable for neutron scattering experiments. La2CoO4+ single crystals were grown by the Travelling Solvent Floating Zone (TSFZ) without the addition of a solvent but continuously stabilizing the growth conditions. Post synthesis annealing at 500°C in oxygen flux yielded phase pure La2CoO4.25, which was further characterized by single crystal neutron and X-ray diffraction, as well as by electron microscopy (SEM/EDS), revealing its quality in terms of composition, homogeneity and crystalline quality. For La2CoO4.25 a complex structure with a 2D modulation vector related to oxygen ordering was revealed by single crystal X-ray and neutron powder diffraction studies. In addition, magnetic measurements coupled with preliminary single crystal elastic neutron scattering experiments exhibit antiferromagnetic ordering with a Néel temperature of TN = 36 K with a complex magnetic structure involving a doubling of all orthorhombic axes.

Insights into the first multi-transition-metal containing Ruddlesden–Popper-type cathode for all-solid-state fluoride ion batteries

“…55 La 2 CoO 4.25 was shown to order antiferromagnetically at 36 K with both oxygen and charge ordering via neutron diffraction. 56 In contrast, La 2 CoO 4 undergoes a Néel-type order at 275 K and a structural transition at 135 K to the tetragonal phase. 57 For the substituted La 2 Ni 0.75 Co 0.25 O 4.08 composite, no sharp transitions in susceptibility were expected due to the observations on the two parent compounds.…”

Insights into the First Multi-Transition-Metal Containing Ruddlesden Popper-Type Cathode for all-solid-state Fluoride Ion Batteries

“…La2CoO4.25 was shown to order antiferromagnetically at 36 K with both oxygen and charge ordering via neutron diffraction 51 . In contrast, La2CoO4 undergoes a Néel-type order at 275 K and a structural transition at 135 K to the tetragonal phase 52 .…”

Growth of Fe-Substituted Sr6Co5O15 Hexagonal Perovskite Single Crystals by a Flux Method

“…In the following, we use the flux method to explore the preparation of Sr 6 (Co 1– x Fe x ) 5 O 15 single crystals, owing to its simple operation and ease of preparation of high-quality oxide single crystals. ,− 5 g of Sr 6 (Co 1– x Fe x ) 5 O 15 polycrystalline powder and 35 g of K 2 CO 3 (HUSHI, 99.0%) flux were ground for about 1 h and put into the alumina crucible, which was sealed with the high-temperature ceramic sealant before transferring to the muffle furnace. Raise the temperature from room temperature to 930 °C at the rate of 5 °C/min and maintain it at this temperature for 24 h; then cool it down to 800 °C at the rate of 0.5 °C/h, and finally turn off the power supply and wait for it to cool down to room temperature naturally (refer to Method I).…”