Synthesis and magnetic properties of MNb₂O₆(M = Fe, Co, Ni) nanoparticles

Abstract

Considerable efforts have been exerted on the controllable synthesis of columbite niobate ceramics due to their fascinating properties and applications. Especially, it is still a great challenge to fabricate nanostructures of the niobate series. In this research, FeNb 2 O 6 , CoNb 2 O 6 and NiNb 2 O 6 nanoparticles have been successfully prepared via a facile hydrothermal route followed by heat treatment. X-ray powder diffraction patterns show that all the products have the typical orthorhombic columbite structure. The electron microscopy analyses reveal that the obtained nanoparticles have diameters of 50-100 nm. The magnetic property results demonstrate that the magnetically ordered state is hard to observe down to 1.8 K for the FeNb 2 O 6 sample, while the magnetic transition temperatures of T N ¼ 3 K and T N ¼ 6 K can be obtained for CoNb 2 O 6 and NiNb 2 O 6 samples, respectively. A weak ferromagnetic moment can be detected below 5 K for both CoNb 2 O 6 and NiNb 2 O 6 samples. Furthermore, the NiNb 2 O 6 sample even exhibits a metamagnetic transition at 1.8 K due to the spin flipping of the ferromagnetic chains.

Crystal growth and magnetic characterization of a tetragonal polymorph of NiNb2O6

“…Additionally, a significant amount of work has gone into engineering and synthesizing ANb 2 O 6 nanopowders for applications to microwave resonators due to the wide range of magnetic transitions experienced by this family. [8,9,10,11] …”

Oxidative Dehydrogenation of n‐Octane over Niobium‐Doped NiAl2O4: An Example of Beneficial Coking in Catalysis over Spinel

“…The formation of the NiNb 2 O 6 phase (ICDD PDF#00‐032‐0694) was detected when higher concentrations of Nb precursors were used for the syntheses of SP‐0.06 Nb and SP‐0.10 Nb (Figure a). This phase belongs to the columbite family and is known to be inert under oxidative dehydrogenation reaction conditions . Also, there are a few small peaks at 2 θ ≈38°, 43°, and 54°, which belong to the columbite phase .…”

“…This phase belongs to the columbite family and is known to be inert under oxidative dehydrogenation reaction conditions . Also, there are a few small peaks at 2 θ ≈38°, 43°, and 54°, which belong to the columbite phase . In addition, the high intensity of the peaks in the XRD diffractograms suggest a high degree of crystallinity for these catalysts, which is driven by the high‐temperature treatment during the synthesis.…”

“…These catalysts showed hexagonal morphology as shown in Figure a. Both NiAl 2 O 4 and NiNb 2 O 6 have this morphology, and hence they cannot be separately identified . To investigate the distribution of all three elements in these catalysts, energy dispersive X‐ray spectrometry (EDX) mapping analysis was performed in DFSTEM (dark‐field scanning transmission electron microscopy) mode using high‐resolution transmission electron microscopy (HRTEM).…”

Active particles in noninertial frames: How to self-propel on a carousel

“…Finally an ensemble of many particles should be considered in a rotating frame. In a rest frame, collections of circular swimming particles have been studied in various situations [11,12,18,57,86,[99][100][101][102][103][104][105][106][107] and many linear swimmers with inertia have been more recently explored [108]. An open question is whether in a rotating frame there is a gradient of kinetic temperature maintained and how this affects motility-induced phase separation [109,110].…”