Search results for "solution"
showing 10 items of 5638 documents
Formation of complex defects in Mn c Mg 1–c O and Ni c Mg 1–c O single solid solution
2005
The results of investigation of the fast neutron irradiation and thermal treatment on absorption spectra of single solid solution of MncMg1–cO, NicMg1–cO and MgO crystals are presented. It is shown that at impurity ion concentration larger than 0.1 mass.% a probability of formation of aggregate centers consisting of more than three F+- or F-centers is small. After thermal treatment of MncMg1–cO and NicMg1–cO single solid solution irradiated by fast neutrons additional wide bands are observed. We assume that these additional bands belong to complex centers of Mn3+-VMg and Ni3+-VMg. The mechanisms of bands formation are discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase competition in (La1 − c,Src)CoO3solid solutions:ab initiothermodynamic study
2013
Statistical thermodynamics and density functional theory (DFT) formalisms are combined to analyze the phase competition of energetically preferable phases in (La1 − c,Src)CoO3 solid solutions upon LaCoO3 doping with Sr. La/Sr sublattice in ABO3 perovskite structure is considered as immersed in the field of CoO3 units and the superstructures that are stable with respect to the formation of antiphase domains are analyzed. The concentration-dependent energy parameters determining the relative stability of the cubic superstructures (phases) are extracted. This allows us calculations of concentration- and temperature dependences of the long-range order (LRO) parameters for different phases. The …
Structural effects of Co and Cr substitution in LaMnO3 + δ
2000
Series of perovskite oxides with the composition LaMn1 − xMxO3 + δ (M = Cr, Co; 0 ≤ x ≤ 1) have been synthesized by thermal treatment of precursors obtained by freeze-drying of acetic acid solutions. The oxides have been characterized by X-ray diffraction, and the Mn4+ content and, thus, the oxygen excess, δ, has been determined by redox back-titration. LaMnO3.14 and LaCrO3 phases have the rhombohedral-LaAlO3 and the orthorhombic-GdFeO3 structures, respectively. The LaMn1 − xCrxO3 + δ phases have the rhombohedral structure for x ≤ 0.3, and the orthorhombic structure for x ≥ 0.5. LaCoO3 has, as LaMnO3.14, the rhombohedral structure. However, the LaMn1 − xCoxO3 + δ phases have orthorhombic st…
Growth and defect studies of CdTe particles
2013
The paper reports the epitaxial growth of cadmium telluride (CdTe) particles by thermal deposition on cleaved planes of (001)NaCl and (001)KBr. Using high resolution transmission electron microscopy and electron diffraction it was shown that CdTe particles could have different orientation and phase (cubic or hexagonal) depending on the substrate temperature. Their most common defects are twins and stacking faults.
Influence of diamagnetic impurity on mid‐IR absorption in antiferromagnetic insulator NiO
2005
-1 was studied in polycrystalline Ni c Mg 1-c O solid solutions with c=0.99, 0.98, 0.97, 0.95, 0.90, 0.80, 0.70 and 0.60. The composition and temperature dependences of the absorption suggest that the band has magnetic origin re- lated to simultaneous excitation of two-magnons at the Brillouin-zone boundary and one phonon. -1 in polycrystalline NicMg1-cO solid solutions. Polycrystalline solid solutions NicMg1-cO (c=0.99, 0.98, 0.97, 0.95, 0.90, 0.80, 0.70 and 0.60) were prepared using ceramic technology from the appropriate amounts of aqueous solutions of Mg(NO3)2·6H2O and Ni(NO3)2·6H2O salts, which were mixed and slowly evaporated. The remaining dry 'flakes' were heated up to 500-600 oC to…
Magnetic Transitions in the Double Perovskite Sr2FeRe1-xFexO6(0≤X≤0.5)
2008
AbstractThe synthesis, structure, and magnetic and transport properties of solid solutions Sr2FeRe1-xFexO6 (0≤x≤0.5) are reported. A structural evolution in the solid solutions from a double perovskite to perovskite is observed with increasing Fe/Re disorder. Except for the metallic parent compound all members of the series are semiconducting. For the Fe-doped samples a change from ferrimagnetic interactions in the parent compound to a complex superposition of ferrimagnetic and antiferromagnetic interactions was observed. The magnetic moment decreases with x, whereas the Curie temperature TC remains unaffected. The magnetic and Mössbauer data suggest Fe to act as a redox-buffer.
New tubular transition metal oxoanionic derivatives: a systematic approach to condensed phases of the dumortierite family
1993
Abstract An unified synthetic approach has allowed us to isolate a wide set of highly condensed oxoanionic derivatives of transition metals by using solution chemistry procedures. New phases are described [Ni 12+ x H 6−2 x (AsO 4 ) 8 (OH) 6 . Ni 6 (SeO 3 ) 4 (OH) 4 ], and the preparation of other already known [Ni 12+ x H 6−2 x (PO 4 ) 8 (OH) 6 , Ni 3 Te 2 O 6 (OH) 2 ] is significantly simplifi ed. The structure of these derivatives, as well as that of other phases such as M 11 (HPO 3 ) 8 (OH) 6 (M=Zn, Co, Ni), previously characterized by us, can be related to that of the dumortierite mineral. The main features of the tubular channels that characterize this structure and the possibility to …
Electron Diffraction and Imaging of Uncompressed Monolayers of Amphiphilic Molecules on Vitreous and Hexagonal Ice
1993
A new approach is described for probing domains of ordered self-assemblies of amphiphilic monolayers at the aqueous solution interface. The method has potential importance for the study of membrane structure, Langmuir-Blodgett films, and nucleation processes of two-and three-dimensional crystals. Electron diffraction (ED) patterns indicative of two-dimensional crystalline self-assembly were obtained from samples, which were examined by cryo-electron microscopy, of monolayers of water-insoluble amphiphiles on vitrified aqueour substrates. The apparent hexagonal symmetry of an ED pattern from a C(16)H(33)OH monolayer was interpreted in terms of multiple twinning. Monolayers of the CL(31)H(63)…
<title>Origin of visible photoluminescence in NiO and Ni<formula><inf><roman>c</roman></inf></formula>Mg<…
2003
A study of the visible photoluminescence in single-crystal NiO and NicMg1-cO (c = 0.99, 0.98 and 0.95) solid solutions is presented for the first time. Two wide luminescence bands, peaked at approximately 12000 cm-1 and approximately 18500 cm-1, were observed. The dependence of their intensity and position on the excitation energy, temperature, and composition were investigated. We attribute the origin of two photoluminescence bands to the impurity- or defect perturbed Ni2+ excitons.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
X-ray powder diffraction study of the stability of solid solutions in (La1−xGdx)OCl
1996
The formation of the solid solutions in the (La1−xGdx)OCl series was studied by X-ray powder diffraction (XPD) at room temperature in the 2θ region between 6.5 and 120°. The Rietveld profile refinement analyses of the XPD patterns were carried out with the background, unit cell, atomic position, isotropic temperature, and Gaussian profile form parameters refined freely. All (La1−xGdx)OCl samples possessed the tetragonal PbFCl-type structure with P4/nmm as the space group (Z=2). The unit cell parameters a and c evolve smoothly through the series and no clustering of the Gd3+ ions was observed according to Vegard's law. The solid solubility exists throughout the whole series. The valence bond…