Search results for "Solid solution"
showing 10 items of 308 documents
Effect of TiO2 on the mullite formation and mechanical properties of alumina porcelain
2010
Abstract The effect of adding TiO 2 to standard alumina porcelain on its microstructure and flexural strength was investigated. A series of alumina porcelain bodies containing increasing amounts of TiO 2 were prepared by extruding mixtures of raw materials and TiO 2 . Porcelain rods were fired under industrial scheduling in a manufacturing kiln. The overall degree of crystalline and amorphous phase content within the porcelain bodies was quantitatively determined using a Rietveld analysis. Results indicated a higher amount of mullite formation in porcelain bodies containing TiO 2 . Examination of the product materials using field emission scanning electron microscopy showed a high density o…
Magnetic Ion Exchange Interactions in NiO—MgO Solid Solutions
2006
In this work, a review of recent experimental data and their interpretation for NicMg1−c O solid solutions is given. In particular, the influence of exchange interactions between Ni2+ ions on the structural, optical, magnetic, and vibrational properties is discussed.
Near-infrared luminescence of isolated and exchange-coupled Ni2+ ions in NicMg1−cO solid solutions
1997
NicMg1−cO (0.01 ⩽ c ⩽ 1) solid solutions were studied by near-infrared luminescence, optical absorption and X-ray absorption spectroscopies. It was found that Ni2+ ions form at c < 0.2 the exchange-coupled pairs, strongly bound via 90 ° super-exchange interactions, and are displaced at c ⩽ 0.6 to the ‘off-center’ positions. This explains the origin of the zero-phonon line splitting observed in the optical absorption and luminescence spectra. It was also found that the effective energy transfer from the single Ni2+ ions to the exchange-coupled Ni2+-Ni2+ pairs occurs at temperatures below 40 K.
Jahn-Teller distortion aroundFe4+inSr(FexTi1−x)O3−δfrom x-ray absorption spectroscopy, x-ray diffraction, and vibrational spectroscopy
2007
$\mathrm{Sr}({\mathrm{Fe}}_{x}{\mathrm{Ti}}_{1\ensuremath{-}x}){\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$ perovskites (strontium titanate ferrite solid solution) with well-defined oxygen stoichiometry have been studied as a function of iron concentration by x-ray diffraction, Fe and Ti $K$-edge x-ray absorption spectroscopy (XAS), and vibrational (Raman and infrared) spectroscopy. In reduced $\mathrm{Sr}({\mathrm{Fe}}_{x}{\mathrm{Ti}}_{1\ensuremath{-}x}){\mathrm{O}}_{3\ensuremath{-}x∕2}$ samples, the analysis of the Fe $K$-edge extended x-ray absorption fine structure indicates the expected presence of oxygen vacancies ${\mathrm{V}}_{\mathrm{O}}^{∙∙}$ in the first coordination shell…
High-resolution characterization of the diffusion of light chemical elements in metallic components by scanning microwave microscopy
2014
International audience; An original sub-surface, high spatial resolution tomographic technique based on scanning microwave microscopy (SMM) is used to visualize in-depth materials with different chemical compositions. A significant phase difference in SMM between aluminum and chromium buried patterns has been observed. Moreover this technique was used to characterize a solid solution of a light chemical element (oxygen) in a metal lattice (zirconium). The large solubility of the oxygen in zirconium leads to modifications of the properties of the solid solution that can be measured by the phase shift signal in the SMM technique. The signal obtained in cross-section of an oxidized Zr sample s…
V-containing ZrO2 inorganic yellow nano-pigments
2015
In this work we report new results on the preparation, characterization and color properties of the inorganic yellow nano-pigmenting system based on monoclinic V–ZrO2 solid solution nanoparticles. The series of solid solution nanopowders were obtained by a polyol technique where the precipitates, obtained after heating at 180 °C ethylene glycol solutions of vanadyl acetonate and zirconium n-propoxide, were annealed at different temperatures up to 1300 °C for a short duration, in order to improve their crystallinity and control the crystalline form of the final nanoparticles. On annealing at around 450 °C highly crystalline tetragonal V-containing zirconia particles were developed, which tra…
Microstructure of Fe–ZrSiO4 solid solutions prepared from gels
2012
Abstract Microstructural changes associated with chemical and structural evolution from gels to Fe x –ZrSiO 4 solid solutions are reported. Mineralizer-free Fe x –ZrSiO 4 gels in the compositional range 0 ≤ x ≤ 0.15 were prepared by sol–gel liquid-phase route from mixtures of alkoxides of silicon and zirconium, and iron (III) acetylacetonate, and annealed at different temperatures and/or times. The first step on the whole process to the final Fe x –ZrSiO 4 solid solutions was the formation of aggregated of tetragonal Fe-doped ZrO 2 nanocrystals with diameters smaller than 50 nm. At this stage the tetragonal Fe–ZrO 2 were embedded in amorphous silica resulting nanocomposite materials. The …
Microstructural Evolution from Praseodymium-Containing Zircon Gels to Prx-ZrSiO4 Solid Solutions
2012
Structural evolution and coupled microstructural transformations occurred on annealing mineralizer-free Pr-containing ZrSiO4 gels up to final praseodymium-doped zircon yellow pigments are reported. Gels with nominal compositions Prx-ZrSiO4, 0 ≤ x ≤ 0.125, were prepared from mixtures of zirconium and silicon alkoxides and praseodymium acetylacetonate. Crystallization pathway and microstructural changes of thermally treated dried gels were followed by infrared spectroscopy, X-ray diffraction, field emission scanning and transmission electron microscopies, respectively. Results indicated that the crystallization pathway through the whole process of final Prx-ZrSiO4 solid solutions formation di…
Synthesis and characterization of praseodymium-containing ZrSiO4 solid solutions from gels
2011
Abstract The preparation and characterization of a series of praseodymium–zircon solid solution (Prx–ZrSiO4) materials with increasing nominal amounts of Pr is reported. Pr-doped zircon gels were prepared by gelling mixtures of zirconium n-propoxide, praseodymium acetylacetonate and tetraethylorthosilicate, and annealed over the range of temperature up to the formation of Pr–zircon solid solutions. The reaction sequence was followed by X-ray powder diffraction (XRD), ultraviolet–visible diffuse reflectance (DR) and infrared spectroscopy (IR). The first crystalline phase detected on annealing gels was a tetragonal praseodymium-containing ZrO2 phase (t-Pr–ZrO2). On further annealing, the subs…
The stoichiometry of blue vanadium doped zircon obtained by sol-gel methods
1992
Abstract In this study, Sol-Gel processes in aqueous solution were used to investigate the stoichiometry of the V/1bZrSiO 4 solid solutions achieved by this method. Compositions with a formal stoichiometric defect in: (a) ZrO 2 ([ZrO 2 ] 1−2x [SiO 2 ] [V 2 O 5 ] x ), and (b) in SiO 2 ([ZrO 2 ] [SiO 2 ] 1−2x [V 2 O 5 ] x ), x=0.02, 0.04, 0.05 and 0.10 have been prepared. X Ray Diffraction analyses in fired samples (1200°/3 days) showed that cristobalite and monoclinic zirconia appear as residual crystalline phase in (a) and (b) compositions respectively, except in sample (a) with x=0.02 in which no residual phase was detected and therefore is considered stoichiometric. This sample and sample…