Limits of Solid Solution and Evolution of Crystal Morphology in (La_1–xRE_x)FeO₃ Perovskites by Low Temperature Hydrothermal Crystallization

Abstract

The crystallization of a new series of A-site substituted lanthanum ferrite materials (La 1– x RE x )FeO 3 was explored by the hydrothermal method at 240 °C, for rare earth (RE) = Nd, Sm, Gd, Ho, Er, Yb, and Y, with 0 ≤ x ≤ 1. The effect of elemental substitution on the morphological, structural, and magnetic properties of the materials was studied using high-resolution powder X-ray diffraction, energy dispersive spectroscopy (EDS) on the scanning electron microscope, Raman spectroscopy, and SQUID magnetometry. If the radius of the La 3+ and the substituent ions is similar, such as for Nd 3+ , Sm 3+ , and Gd 3+ , homogeneous solid solutions are formed, with the orthorhombic GdFeO 3 -type structure, and a continuous evolution of Raman spectra with composition and distinct magnetic behavior from the end members. When the radius difference between substituents and La 3+ is large, such as for Ho 3+ , Er 3+ , Yb 3+ , and Y 3+ , then instead of forming solid solutions, crystallization in separate phases is found. However, low levels of element mixing are found and intergrowths of segregated regions give composite particles. In this case, the Raman spectra and magnetic behavior are characteristic of mixtures of phases, while EDS shows distinctive elemental segregation. A-site replacement induces an evolution in the crystallite shape with an increasing amount of substituent ions and this is most evident for RE = Y from cube-shaped crystals seen for LaFeO 3 to multipodal crystals for (La 1– x Y x )FeO 3 , providing evidence for a phase-separation-driven evolution of morphology.

Role of Er doping on isoamyl alcohol sensing performance of LaFeO3 microspheres and its prospects in wheat mildew detection

“…XRD patterns of SEr0, SEr1, SEr5, and SEr10 demonstrate that there is no new phase produced with the content of doped Er increasing, and it is distinct that the highest peak shifts to the right as the doping concentration enhances (Fig. 1), which is consistent with the research of Jia et al 38 As the smaller atomic radius Er 3+ (0.881 Å) shows, the cells of LaFeO 3 tend to shrink and the lattice spacing is reduced, causing the main peak diffraction peak to deviate at a larger angle. 39 With the increase in Er doping (from 0 to 5%), the grain size of the doped phase is smaller than that of the pure phase, whereas, as the doping amount reaches 10%, the grain size of the doping amount will increase slightly (Table S2†), which can be attributed to the lower main peak intensity of SEr10.…”

Structural and Magnetic Properties of Perovskite Functional Nanomaterials La1−xRxFeO3 (R = Co, Al, Nd, Sm) Obtained Using Sol-Gel

“…As the Nd 3+ content increased, the remanent magnetization and saturation magnetization of the samples first increased then decreased. The magnetic moment and ionic radius of rare earth elements ions are the main factors affecting the saturation magnetization of the doping samples [37]. The coercivity of the samples shows an upward trend, and the main factors affecting the coercivity of the samples include magnetic anisotropy, grain size, micro strain, stress, crystal symmetry and spin-orbit coupling effect, magnetic single domain size, and impurities [31].…”

“…Table 12 shows the distribution of magnetic parameters of the sample. This may be because the Sm 3+ ions are magnetic in nature [37], and together with Fe 3+ and O 2− , generate a super-exchange interaction, which affected the net magnetic moment size of the crystals, ultimately affecting the magnetization of the samples. Figure 21 shows the hysteresis loop of the uncalcined La 1−x Sm x FeO 3 (x = 0~0.5) samples.…”