Phase equilibria of the Al-Co-Er system at 400°C and 600°C

The 400?C and 600?C isothermal sections of the Al-Co-Er system were studied assisted with X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) techniques. 18 three-phase fields were identified in the 400?C isothermal section. The maximum solid solubilities of Al in Co3Er and Co2Er were 13.93 at.% and 16.13 at.%, respectively. Whereas the maximum solid solubilities of Co in Al2Er, Al2Er3 and AlEr2 were 6.93 at.%, 6.65 at.%, and 6.49 at.%, respectively. And the solid solution range of ? is from 22.22 at.% Al to 44.44 at.% Al. While the 600?C isothermal section included 20 three-phase fields. The maximum solid solubilities of Al in Co17Er2 and Co7Er2 were 10.17 at.% and 10.24 at.%, respectively. Whereas the maximum solid solubilities of Co in Al2Er and Al2Er3 were 3.63 at.% and 2.01 at.%, respectively.

Crystal structure solution for the A 6 B 2O17 (A = Zr, Hf; B = Nb, Ta) superstructure

Zr6Ta2O17, Hf6Nb2O17 and Hf6Ta2O17 crystal structure solutions have been solved using synchrotron X-ray powder diffraction and neutron powder diffraction in conjunction with simulated annealing, charge flipping and Rietveld refinement. These structures have been shown to be isomorphous with the Zr6Nb2O17 superstructure, leading to the classification of the A 6 B 2O17 (A = Zr, Hf; B = Nb, Ta) orthorhombic compound family with symmetry Ima2 (No. 46). The asymmetrical structural units of cation-centred oxygen polyhedra used to build the structure are as follows: (i) one set of symmetry-equivalent six-coordinated polyhedra, (ii) three sets of symmetry-equivalent seven-coordinated polyhedra and (iii) one set of symmetry-equivalent eight-coordinated polyhedra. The potential for cation order and disorder was discussed in terms of cation atomic number contrast in X-ray and neutron powder diffraction as well as the bond valence method. In addition, the structural mechanisms for experimentally observed compositional variations within the solid solution range can be attributed to the addition or removal of a set of symmetry-equivalent seven-coordinated polyhedra accompanied by corresponding oxygen tilts within the A 6 B 2O17 structure.

First-principles electronic structure calculations for the whole spinel oxide solid solution range MnxCo3−xO4 (0 ≤ x ≤ 3) and their comparison with experimental data

Transition metal spinel oxides have recently been suggested for the creation of efficient photovoltaic cells or photocatalysts.

Type II Bi1 − x W x O1.5 + 1.5x : a (3 + 3)-dimensional commensurate modulation that stabilizes the fast-ion conducting delta phase of bismuth oxide

The Type II phase in the Bi1 − x W x O1.5 + 1.5x system is shown to have a (3 + 3)-dimensional modulated δ-Bi2O3-related structure, in which the modulation vector ∊ `locks in' to a commensurate value of 1/3. The structure was refined in a 3 × 3 × 3 supercell against single-crystal Laue neutron diffraction data. Ab initio calculations were used to test and optimize the local structure of the oxygen sublattice around a single mixed Bi/W site. The underlying crystal chemistry was shown to be essentially the same as for the recently refined (3 + 3)-dimensional modulated structure of Type II Bi1 − x Nb x O1.5 + x (Ling et al., 2013), based on a transition from fluorite-type to pyrochlore-type via the appearance of W4O18 `tetrahedra of octahedra' and chains of corner-sharing WO6 octahedra along 〈110〉F directions. The full range of occupancies on this mixed Bi/W site give a hypothetical solid-solution range bounded by Bi23W4O46.5 (x = 0.148) and Bi22W5O48 (x = 0.185), consistent with previous reports and with our own synthetic and analytical results.

Analysis of selective vaporization behavior in laser melting of magnesium alloy by plume deposition

Laser surface melting is one of the most important processes in laser material processing. Selective vaporization of alloying elements in laser melting offers fundamental understanding of laser processing on metallic alloys. This work provides linkage between laser melting and material properties using secondary ion mass spectrometry (SIMS) for tiny vaporized species in laser-generated plume and energy dispersive spectroscopy (EDS) for solid solution range in molten pool, both qualitatively and quantitatively (up to hundreds of micron). Silicon wafer was used to collect the generated plume. Chemical analysis was carried out on top surface and sub-surface of the deposited plume. Transport behavior as well as distribution of the vaporized species inside the plume was further proposed.