Magnetic properties of Nd-Fe-B-Co-Al alloy magnets have been studied with respect to both boron and aluminum concentration. Both cobalt and aluminum substitution for iron is remarkably effective for increasing magnetic hardness in the low boron concentration region. The following magnetic properties were attained for Nd 15 Fe 62.5 B 5.5 Co 16 Al 1 : Br=13.2KG, iHc=11.0kOe, (BH) max =41.0MGOe and T c =500°C. The reversible temperature coefficient of remanence in the above magnet was -0.071%/°., approximately one-half that for the Nd 15 Fe 77 B 8 magnet. It was observed that Laves phase Nd(Fe, Co) 2 precipitates in cobalt containing magnets. The authors think that the addition of aluminum makes this Nd(Fe, Co) 2 magnetic phase non-magnetic; which is considered to be the cause of coercivity increase.
An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The slight incommensurate modulation of the structure of Bi2Mn4/3Ni2/3O6 is sufficient to suppress the electrical polarization which arises in commensurate treatments of the structure, due to antiferroelectric coupling of local polar units of over 900 Å3. The incommensurate structure is produced by the competition between ferroelectric Bi lone pair-driven A site displacement, chemical order of Mn and Ni on the B site, and both charge and orbital order at these transition metals. The interplay between the frustrated polar Bi displacements and the frustrated spin order at the B site, induced by positional disorder, produces magnetodielectric coupling between the incommensurately modulated lattice and the spin-glass-like ground state with an unusual relationship between the magnetocapacitance and the applied field.
The piezoelectric devices widespread in society use noncentrosymmetric Pb-based oxides because of their outstanding functional properties. The highest figures of merit reported are for perovskites based on the parent Pb(Mg1/3Nb2/3)O3 (PMN), which is a relaxor: a centrosymmetric material with local symmetry breaking that enables functional properties, which resemble those of a noncentrosymmetric material. We present the Pb-free relaxor (K1/2Bi1/2)(Mg1/3Nb2/3)O3 (KBMN), where the thermal and (di)electric behavior emerges from the discrete structural roles of the s0 K+ and s2 Bi3+ cations occupying the same A site in the perovskite structure, as revealed by diffraction methods. This opens a distinctive route to Pb-free piezoelectrics based on relaxor parents, which we demonstrate in a solid solution of KBMN with the Pb-free ferroelectric (K1/2Bi1/2)TiO3, where the structure and function evolve together, revealing a morphotropic phase boundary, as seen in PMN-derived systems. The detailed multiple-length-scale understanding of the functional behavior of KBMN suggests that precise chemical manipulation of the more diverse local displacements in the Pb-free relaxor will enhance performance.
The two-dimensional polyhedral anion network melilites La1+xSr1−xGa3O7+0.5x exhibit interstitial oxide ion conductivity. The solid solution is shown to extend to x = 0.64, and the variation of the conductivity with x is investigated. At high temperatures, all of these compounds adopt the typical tetragonal melilite structure. When x > 0.6, cooling below 600 °C results in a reversible phase transition to an orthorhombic structure which reduces the ionic conductivity. Quenching experiments have shown the tetragonal structure has a higher conductivity compared to the orthorhombic structure of the same composition. Short-range order effects associated with this transition exercise an important influence on the composition- and temperature-dependence of the conductivity.
Der zweite Satz auf S. 8730 dieser Zuschrift enthält einen Fehler. Dieser Satz lautet korrekt: “The ratio of intensities of acetylene to aromatic peaks was calculated using variable-contact-time 1H–13C CP/MAS NMR spectra with the following results: CMP-1 0.27 (expected value 0.40); CMP-2 0.18 (expected value 0.25); CMP-3 0.10 (expected value 0.18).” Die Autoren entschuldigen sich für dieses Versehen, das keine Auswirkungen auf die Schlussfolgerungen des Beitrags hat. Dedicated to Colonel Joseph Hutchison on the occasion of his 70th birthday
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Magnetic properties of Nd-Fe-B based magnets with both cobalt and aluminum addition have been investigated with respect to cobalt and aluminum concentration. Structural analyses were carried out for the sintered bodies. In cobalt containing alloys, Nd(Fe,Co) 2 phase was clearly observed by X-ray diffractometer, SEM and TEM, especially for the magnet with more than 30 at % cobalt. The coercive force behavior versus aluminum content for cobalt containing magnets can be divided into two stages. The first stage in which coercive force increases abruptly with the small amount addition of aluminum may result from Nd(Fe,Co) 2 phase being nonmagnetic by the addition of aluminum. The quantity of this Nd(Fe,Co) 2 phase increases with increasing cobalt content. It was shown that the greater the quantity of cobalt in the sintered body, the greater the addition of aluminum becomes necessary for obtaining high coercive force.
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