Heteroleptic Complexes of Zirconium Acetylacetonates: Better Precursors for the Preparation of Zirconia. Structural Characterization of [(acac)2Zr{ONC(Me)py‐2}2]

The reactions of the heteroleptic zirconium diisopropoxide bis(acetylacetonate) in benzene solution with two equivalents of oximes, alkoxyalkanols, triphenylsilanol and trimethylsilyl acetate yield products with the formula [{MeC(O)CHC(O)Me}₂ZrL₂] with L = —ONC(Me)C₅H₄N‐2, —ONC(Me)C₄H₃O‐2, —OCH₂CH₂OR (R = Me, Et, Buⁿ; py = pyridine, fu = furan), —OSiPh₃ and —OSiMe₃. Most of these derivatives are solids, but the [(acac)₂Zr(OSiMe₃)₂] is a viscous oil. They could be purified either by recrystallization or by vacuum distillation; all of these are monomeric in boiling benzene. Their elemental analyses, molecular weight measurements and IR as well as NMR spectra were measured. The oximato complex [(acac)₂Zr{ONC(Me)py‐2}₂] has been shown by single crystal X‐ray crystallography to be monoclinic and mononuclear in the solid state, where zirconium has the coordination number 8; all the ligands are situated in cis‐ position and the oximato ligand binds via N and O in a dihapto (η²‐N, O) manner.     

Chemistry of oxomolybdenum(V) and (VI) complexes incorporating oxygen,nitrogen and/or sulfur donor atoms. Part 1. Synthesis and characterization of [Mo2O3L4] (LH = HSCH2CH2CO2H,HSCH2CO2Me or HSCH2CH2CO2Me) and [MoO2L′2] (L′H = HOC6H4NH2, HOCH2C6H4NH2, HOC6H4CHO or HOC10H8N)

Reactions of an acidified aqueous solution of Na₂MoO₄ · 2H₂O with 3-mercaptopropionic acid, 2-mercaptomethylethanoate and 3-mercaptomethyl propanate yield blue oxo-bridged Mo^V complexes of the type [Mo₂O₃L₄], whereas corresponding reactions with 2-aminophenol, 2-aminobenzyl alcohol, salicylaldehyde and 2-methyl-8-hydroxyquinoline, yield yellow dioxomolybdenum(VI) complexes, [MoO₂L′₂]. All these coloured solids are sparingly soluble, even in coordinating solvents. They have been characterized by elemental and spectroscopic analysis.     

Magnetic and optical properties of Gd-Tl substituted M-type barium hexaferrites synthesized by co-precipitation technique

The substitution of numerous cations into hexagonal ferrite has been extensively used to endow novel properties and functionalities for various applications. In the present work Gd-Tl substituted barium hexaferrites prepared by co-precipitation process, having the composition Ba_0.75Cu_0.25(Gd_xTl_0.5-x)Fe_11.5O₁₉ (x = 0.0, 0.25 and 0.50). The hexaferrite formation during calcination of sample x = 0.25 was confirmed by TGA/DSC which was processed at 1000 °C for 3 h. The analysis of X-ray diffraction depicts the existence of magneto-plumbite structure with the formation of a minor secondary α–Fe₂O₃ phase x ≤ 0.0 and BaFe₂O₄ phase x ≤ 0.50. UV–Vis spectra reveal the dropping down behavior in the optical energy band gap from 2.47 eV to 1.74 eV. The grains with hexagonal platelet-like shape having size of 0.415–0.446 μm of magnetic powder nanoparticles (MPs) are observed by SEM images. The energy dispersive spectrometer (EDS) analysis was employed for presence of ferrite elements within a single particle. Hysteresis loops signifies the magnetization (M_s) and remnant magnetization (M_r) first increases up to x = 0.25 then reduces with the substitution (x) increment; contrarily, the coercivity (H_c) exhibited initially decreased with maximum content of Tl at x = 0.0 then increases at x = 0.25 after that it decreases at x = 0.50. Maximum values such as M_s (51.727 emu/g), M_r (28.061 emu/g), and H_c (4.057 kOe) are attained for x = 0.25 at room temperature. The synthesized magnetic nanoparticles are found to be suitable for microwave absorbing materials, permanent magnets, catalyst, high density recording media and optoelectronic devices.     

New sol–gel precursors for binary oxides of antimony,Sb<Subscript>2</Subscript>O<Subscript>3</Subscript> (senarmonite) and α-Sb<Subscript>2</Subscript>O<Subscript>4</Subscript>: synthesis and characterization of some ketoximate modified antimony(III) alkoxides

Hydrolysis of pure Sb(OPrⁱ)₃ by sol–gel method followed by sintering at 500 °C yields microcrystallites of Sb₂O₃ (senarmonite phase). Under similar conditions bimetallic alkoxide, [NaSb(OPrⁱ)₄], yields a mixture of binary oxides Sb₂O₃ and Sb₂O₄. Chemical modification of Sb(OPrⁱ)₃ with oximes forms monomeric products of the type [Sb(OPrⁱ)_3−n {ON=C(CH₃)R} _n ] {where R = CH₃, n = 1 [1]; n = 2 [2]; n = 3 [3]; R = 2-C₅H₄N, n = 1 [4]; n = 2 [5]; n = 3 [6]; R = 2-C₄H₃O, n = 1 [7]; n = 2 [8]; n = 3 [9]; R = 2-C₄H₃S, n = 1 [10]; n = 2 [11]; n = 3 [12]}. The liquid products [1–3, 7 & 10] were purified by distillation while the solids by recrystallization. All these products were characterized by elemental analyses, IR, NMR (¹H and ¹³C{¹H}) and representative derivatives [1], [2] and [3] by FAB mass studies. On the basis of these studies, a distorted pyramidal structure for all the derivatives may be assumed in the solution state containing an end-on coordination of oximes with the metal atom. Hydrolysis of the distilled precursors [1], [2] and [3] under sol–gel conditions yields pure nano-sized α-Sb₂O₄. All the oxides were characterized by XRD, SEM and EDX analysis exhibiting minimum particle size for the oxide obtained from the precursor [3].     

In-plane magnetization with high coercivity in terbium iron garnet thin films deposited on Pt/Si substrate by PLD

We report on the growth of terbium iron garnet (TbIG, Tb₃Fe₅O₁₂) thin films having anomalously large coercivity and in-plane easy axis of magnetization. The TbIG thin films were prepared at room temperature (RT) on Pt/Si(1 0 0) substrates by pulsed laser deposition technique. The films deposited at RT were X-ray amorphous and do not show any magnetic order. Annealing of the RT deposited film at 900 °C resulted into fully textured (532) TbIG film. Atomic force microscopy and cross-sectional scanning electron microscopy studies of the TbIG films showed good surface quality with an average surface roughness of 5.0 nm and thickness of about 300 nm, respectively. The M-H loops measured at 20 K for TbIG films, exhibit about an order of magnitude enhancement in the coercivity value (H_c) than the single crystal. In-plane and out-of-plane M-H loops revealed that the easy axis of the magnetization lies within the film’s plane. In-plane magnetization combining with large H_c value of the TbIG thin film may be of scientific interest for the possible applications.     

Stability of nonthermodynamic equilibrium cation distribution frozen during pulsed laser deposition of Co-ferrite thin films

Co-ferrite thin films were prepared by pulsed laser deposition technique at room temperature, and magnetization was studied as a function of annealing temperature (T _A ) and annealing time. One set of films was quenched immediately after annealing while the other set was furnace cooled. Spontaneous magnetization value, 4π M _S , of the quenched films was observed to be higher than the furnace cooled films in all the cases. Magnetization increases monotonically up to T _A =650°C and then became nearly constant with the increase in T _A . Magnetization values even higher than the Co-ferrite bulk value of 5300 G was observed in the quenched films annealed at and above 650°C. In the case of furnace cooled films, magnetization decreased with the increase in annealing time, while it remained nearly constant in quenched films. Coercivity values of the quenched films were always found to be lower than those of the furnace cooled films. The observed magnetic properties in the films were attributed to the cation distribution and the grain sizes.     

Charge in cosmological models

The balanced field equations due to Penney are used to find solutions for cosmological models in the presence of charge. Herein, it is found that the introduction of charge adds additional terms to the Einstein conservation equation and distribution expressions. The curvature parameter is affected and it is concluded that whereas matter affects it positively, the charge does so negatively. There then arises also the possibility of an evolution of local systems against the background of a global expansion.     

Correlation of plasma electron temperature with neutron emission ina low-energy plasma focus

Correlation of neutron emission with plasma electron temperature in a low-energy (2.3 kJ) plasma focus is investigated. To determine the plasma temperature by continuum X-ray analysis, cobalt is selected as the filter, which discriminates the line radiation from the background impurities like carbon, nitrogen, and oxygen, or the copper of which plasma focus electrodes are made. For a pressure range of high neutron emission (1-4 mbar), the neutron yield is found to correlate with the plasma temperature. The highest temperature recorded is 5 keV at 2.5 mbar, the filling pressure for the highest neutron emission in this device