Crystal Shape Tailoring in Perovskite Structure Rare-Earth Ferrites REFeO₃ (RE = La, Pr, Sm, Dy, Er, and Y) and Shape-Dependent Magnetic Properties of YFeO₃

Abstract

Controllable growth of perovskite oxide with tailored shapes is challenging but promising for shape-dependent physical and chemical property studies and probable applications. In this article, we report a general method for tailoring the crystal shape of perovskite structure rare-earth ferrite (REFeO3) crystals in hydrothermal conditions. By adjusting the ratio of KOH to urea, various shapes of REFeO3 crystals can be prepared, such as LaFeO3 truncated cubes, PrFeO3 perpendicular cross prisms, SmFeO3 crossed bars with trustum, DyFeO3 double pyramids on cubes, ErFeO3 distorted octahedrons, and YFeO3 long bars and thick hexagonal elongated plates. Detailed shape tailoring conditions for each phase of the crystals have been discussed clearly. The structure-dependent shape growing mechanism for each REFeO3 is generally discussed by consideration of the variance of reduced unit cell parameters in reference to the ideal cubic ABO3 perovskite structure. DyFeO3 was taken as an example to elucidate the crystal shape formation mechanism based on the Bravais–Friedel–Donnay–Harker theory. The magnetic property of the YFeO3 crystal shows shape dependence: elongated bars have the highest saturated magnetization, while the lowest coercive field, while the tailored polyhedrons are vice versa. This paper not only builds a general technique for tailoring the crystal shape to various shapes of REFeO3 crystals but also provides many crystals for further study and application of anisotropy either in physical or in chemical properties.

Structure-Controllable Synthesis of Multiferroic YFeO3 Nanopowders and Their Optical and Magnetic Properties

“…As a typical one of the second generation multiferroic materials, YFeO 3 , with its low Curie temperature (~−256 °C) and high Neel temperature (~370 °C), can couple both ferroelectric and anti-ferromagnetic orderings [1,2,3,4,5,6]. It is known that orthorhombic YFeO 3 possesses significant magnetic properties, while the hexagonal YFeO 3 owns better photocatalytic properties and a smaller optical band gap (1.96 eV) [7].…”

Hydrothermal microwave‐assisted synthesis of LaFeO3 catalyst for N2O decomposition

“…The difference in the particle size is clearly seen: the LFO‐MW sample obtained via a microwave‐assisted synthesis mainly consists of particles of 5‐10 µm, while the LFO‐T sample synthesized at conventional conditions contains larger particles of up to 40 µm. Some particles obtained at thermal conditions have truncated facets, which can be produced during conventional hydrothermal synthesis using urea only 77,86 . L. Yuan et al 86 proposed that facet tailoring in LaFeO 3 can be dependent on a capping effect of NH 4 + ions on the FeO 6 octahedron, which means the distortion of FeO 6 in the crystal structure.…”

“…Some particles obtained at thermal conditions have truncated facets, which can be produced during conventional hydrothermal synthesis using urea only 77,86 . L. Yuan et al 86 proposed that facet tailoring in LaFeO 3 can be dependent on a capping effect of NH 4 + ions on the FeO 6 octahedron, which means the distortion of FeO 6 in the crystal structure. However, after the hydrothermal microwave‐assisted synthesis, truncation of faces is not observed, even with a change in the urea concentration and a change of the synthesis parameters (time and temperature of the process).…”

Morphology, Structure Evolution and Site‐Selective Occupancy of Eu3+ in Ca10(PO4)6(OH)2 Nanorods Synthesized via Subcritical Hydrothermal Method

“…The facet‐dependent growth of hydroxyapatite nanocrystals depends on the relative growing speed along <001> direction. Crystal shape could be affected by the mineralizer type and concentration,, solvent polarity, pressure etc, which determine the crystallization rate by reactant ionic attachment on the surface after nucleation. Generally, {100} facets (5.9 * 10 −6 U 0 ) of hydroxyapatite show much higher surface energy than that of {001} facets (3.9 * 10 −5 U 0 ), which means a higher crystal growth rate along <001> direction.…”