Synthesis and Structural Characterisation of Yttrium-Doped α-Zirconium Phosphate

There has been a considerable amount of interest in the ion-exchange properties of layered zirconium phosphates. Potential applications in the remediation of nuclear waste have renewed interest in these inorganic materials, due to their high stability under the acidic conditions typically found in legacy waste pools. It has been well documented that the substitution of metals with different ionic radii into the frameworks of inorganic materials can alter the chemical properties including ion-exchange selectivity. The work presented here focusses on the synthesis and characterisation of yttrium-doped α-zirconium phosphates which are reported for the first time. Two different synthetic methods were used, reflux and hydrothermal syntheses, and the products were characterised by various methods such as powdered X-ray diffraction, MAS-NMR and scanning electron microscopy. It was found that up to 15% of zirconium could be replaced by yttrium before any noticeable impurity phases could be observed. Rietveld refinement from the doping showed that the products did not obey the Vegard’s law. However, the ion-exchange results clearly showed enhanced capacities and selectivity towards Co2+ ions for the substituted materials.

Composition Dependence of Electronic, Elastic, and Polarization Properties of Wurtzite InxGa1-xN and CdxZn1-xO Ternary Alloys

We report the results of density functional theory calculations of several properties of wurtzite-structured InGaN and CdZnO alloys. It is shown that the investigated properties, including the internal parameter, bandgap, mechanical moduli, and electric polarization are nonlinear functions of alloy composition, as they deviate from the linear behavior predicted by Vegard’s law. Based on these results, InGaN and CdZnO are materials whose properties can be tuned via In and Cd concentrations. The spontaneous and piezoelectric polarizations considerably affect the properties of alloys-based devices due to the huge electric fields that build up at the heteroineterfaces. In this work we propose a method of controlling such fields by employing the composition dependence of the total polarization. We support this proposal by showing that, in the case of InGaN, an optimal alloy composition can be found that effectively reduces the polarization-induced electric fields, thereby improving the efficiency of optoelectronic applications.

Structural, Electronic and Optical Properties of ScxGa1-xP Alloys An: Ab Initio Study

The structural, electronic and optical properties of the of ScxGa1-xP alloys have been investigated by using the full-potential plane-wave FP-LAPW method as implemented in the Wien2k code. The exchange-correlation (XC) energy of electrons was treated using the Perdewe-Burke-Ernzerhof parametrization (PBEGGA), and the Tran-Blaha modified Beck-Johnson potential (TB–mBJ). The lattice constant and the bulk modulus have been calculated and analyzed where a deviation from Végard’s law is observed for both. The calculation of the band structure of binary GaP shows that there is an indirect gap of 2.27 eV, while for the ScxGa1-xP compounds there are direct gaps with values of 1.91 eV, 1, 39 eV, 2.04 eV and 1.849 eV for x = 0.25, 0.5, 0, 75 and 1, respectively. At ambient pressure, the refractive index and the dielectric constant are in good agreement with the experimental results. The extinction coefficient does not begin to increase until a threshold, which represents the optical gap. This threshold is equal to 1.224 eV and it starts to increase to reach a maximum at an energy of 3.551 eV.

Effect of phosphorus on the density and molar volume of Al–Si alloy without solidification shrinkage

The Al–Si alloys exhibit many unique properties, but not enough work has been dedicated to their thermophysical properties. In this work, the effect of phosphorus modifier on the density, molar volume and solidification shrinkage rate of Al-25% Si alloys was investigated by using the indirect Archimedes method. The results show that both density–temperature and molar volume–temperature curves show three inflection points: the liquidus temperature point, the eutectic transformation starting point and the finishing point. The density of the solidus linearly decreases and that of the liquidus linearly increases with phosphorus modifier content. Compared with Vegard’s law, the molar volumes show a negative deviation. Finally, the solidification shrinkage rate is calculated from the densities of solidus and liquidus.

Progressive Polytypism and Bandgap Tuning in Azetidinium Lead Halide Perovskites

<div><div><div><p>Mixed halide azetidinium lead perovskites AzPbBr_3-<i>x</i>X<i>_x</i> (X = Cl or I) were obtained by mechanosynthesis. With varying halide composition from Cl- to Br- to I-; the chloride and bromide analogs both form in the hexagonal 6H polytype while the iodide adopts the 9R polytype. An intermediate 4H polytype is observed for mixed Br/I compositions. Overall the structure progresses from 6H to 4H to 9R perovskite polytype with varying halide composition. Rietveld refinement of the powder X-ray diffraction patterns revealed a linear variation in unit cell volume as a function of the average radius of the anion, which is not only observed within the solid solution of each polytype (according to Vegard’s law) but extends uniformly across all three polytypes. This is correlated with a progressive (linear) tuning of the bandgap from 3.41 to 2.00 eV. Regardless of halide, the family of azetidinium halide perovskite polytypes are highly stable, with no discernible change in properties over more than 6 months under ambient conditions</p></div></div></div>

Progressive Polytypism and Bandgap Tuning in Azetidinium Lead Halide Perovskites

<div><div><div><p>Mixed halide azetidinium lead perovskites AzPbBr_3-<i>x</i>X<i>_x</i> (X = Cl or I) were obtained by mechanosynthesis. With varying halide composition from Cl- to Br- to I-; the chloride and bromide analogs both form in the hexagonal 6H polytype while the iodide adopts the 9R polytype. An intermediate 4H polytype is observed for mixed Br/I compositions. Overall the structure progresses from 6H to 4H to 9R perovskite polytype with varying halide composition. Rietveld refinement of the powder X-ray diffraction patterns revealed a linear variation in unit cell volume as a function of the average radius of the anion, which is not only observed within the solid solution of each polytype (according to Vegard’s law) but extends uniformly across all three polytypes. This is correlated with a progressive (linear) tuning of the bandgap from 3.41 to 2.00 eV. Regardless of halide, the family of azetidinium halide perovskite polytypes are highly stable, with no discernible change in properties over more than 6 months under ambient conditions</p></div></div></div>

Generalizing the Chiral Self-Assembly of Spheres and Tetrahedra to Non-Spherical and Polydisperse Molecules in (C70)x(C60)(1-x)(SnI4)2

We describe the spontaneous chiral self-assembly of C₇₀ with SnI₄ as well as a mixture of C₆₀ and C₇₀ with SnI₄. Macroscopic single crystals with the formula (C₇₀)_x(C₆₀)_1-x(SnI₄)₂ (x = 0-1) are reported. C₆₀, which is spherical, and C₇₀, which is ellipsoidal, form a solid solution in these crystals, and the cubic lattice parameter of the chiral phase linearly increases as x grows from 0 to 1 in accordance with Vegard’s law. Our results demonstrate that nonspherical particles and polydispersity are not an impediment to the growth of chiral crystals from high-symmetry achiral precursors, providing a route to assemble achiral particles including colloidal nanocrystals and engineered nanostructures into chiral materials without the need to use external templates.<br>

Generalizing the Chiral Self-Assembly of Spheres and Tetrahedra to Non-Spherical and Polydisperse Molecules in (C70)x(C60)(1-x)(SnI4)2

We describe the spontaneous chiral self-assembly of C₇₀ with SnI₄ as well as a mixture of C₆₀ and C₇₀ with SnI₄. Macroscopic single crystals with the formula (C₇₀)_x(C₆₀)_1-x(SnI₄)₂ (x = 0-1) are reported. C₆₀, which is spherical, and C₇₀, which is ellipsoidal, form a solid solution in these crystals, and the cubic lattice parameter of the chiral phase linearly increases as x grows from 0 to 1 in accordance with Vegard’s law. Our results demonstrate that nonspherical particles and polydispersity are not an impediment to the growth of chiral crystals from high-symmetry achiral precursors, providing a route to assemble achiral particles including colloidal nanocrystals and engineered nanostructures into chiral materials without the need to use external templates.<br>

Effect of Cd2+ Substituted Nickel Ferrite oxide (Ni1-xCdxFe2O4) on Magnetic, Dielectric and Structural Properties

The effect of cadmium (Cd2+) substituted at the NiFe2O4 nano materials were this nano material synthesized by auto-combustion technique. The structural analysis confirms that the samples are polycrystalline nature with spinel cubic crystal symmetry. The effect of Cd2+ contains on lattice constants which obeys Vegard's law. The morphological analysis shows that the highly porous structure with spongy like surface morphology. The observed absorption infrared spectra confirm that the exhibits the nano ferrite materials. The magnetic properties measurements reveal that the saturation of magnetization decreases with an increase in constituent Cd2+ in nickel ferrous oxide. The Cd2+ ions present in A-site and Fe3+ are distributed in both tetrahedral and octahedral sites of spinel lattice. The DC measurement shows that the semiconducting behaviour of the prepared Ni1-xCdxFe2O4. The increase in Cd2+ constituent in the nickel ferrite with decrease curie temperature. The dielectric measurement of all samples shows the usual dielectric dispersion with frequency. The impedance spectroscopy analysis suggests grain interior contribution in the conduction process.

Structural properties of CoxCu1−xFe2O4 solid solution**

Crystallography information files (CIF) were designed formed CoxCu1−xFe2O4 solid solution with the substitution factor x=0 to 1 with an increment of 0.1 depending on Vegard's law by using crystallography software. The effect of the substitution factor has been studied on some parameters and properties of the Co-Cu ferrite system, such as the effect of substitution factor on the lattice parameter, the volume of unit cell, and the density of the unit cell. Also, XRD patterns were estimated by crystallography software depending on the mathematical models of XRD. The XRD results showed a slight shift in the peak position varying with the substitution factor, these are due to the change in lattice parameter caused by the substitution of ions with different ionic radii. XRD also showed an increment in peak intensity varying with the substitution factor, that's due to an increase in the concentration of Cu which led to an increase in the density of electrons.