1,721,086 research outputs found
Decomposition of (Sn2xFe1-xSb1-x)O4 solid solutions with x ≤ 0.50
No full textThermal stabilities of the rutile-type (Sn2xFe1xSb1x)O4 solid solutions with x 0:5 were investigated by TG–DTA in flowing O2 up to 1673 K. After thermal analysis the samples were characterised by means of powder X-ray diffraction analysis (XRD), optical and scanning electron microscopy (SEM) observation and electron dispersive spectrometry (EDS) analysis. The decomposition of the solid solution involves the formation of hematite and a volatile Sb oxide, probably Sb4O6. The decomposition temperature increases with the Sn content of the solid solution
Decomposition of (Ti2x,Fe1-x,Sb1-x)O4 solid solutions below 1673 K
No full textThe pseudo-binary TiO2–FeSbO4 system was investigated by means of thermogravimetric analysis below 1673 K in O2. Rutile-type solid solutions were synthesised at 1373 K in O2 by means of a solid state reaction between the two pure end members TiO2 (rutile) and FeSbO4 mixed in stoichiometric amounts. Thermal stability of the (Ti2xFe1−xSb1−x)O4 solid solution increases with rutile content; equimolar (Ti1.00Fe0.50Sb0.50)O4 solid solutions decompose at about 1673 K forming a TiO2-enriched solid solution and FeSbO4, that subsequently decomposes into Fe2O3 (hematite) and a volatile Sb oxide, probably Sb4O6. For compositions characterised by higher Ti content the decomposition temperature is higher than 1673
Combustion of Vanadium-Carbon powder mixtures at low O2 pressure
No full textThe combustion of vanadium-carbon powder mixtures at low O2 pressure was studied. The reaction was ignited toy induction heating; a wave-front was observed propagating throughout the reactants. The combustion temperature, Tc, was higher than the melting point of V and metal particles melted and coalesced during combustion. The analysis of the as-obtained products shows the formation of two isostructural compounds delta-VO1-x and delta-VC1-x , characterized by an fcc structure. The reaction that lead to the formation of the carbide was sustained by the reaction between V and
The crystal structure of (Ho0.50Ca0.50)MnO3 and its evolution with Cr doping: a Rietveld refinement investigation
No full textSingle-phase sHo0.50Ca0.50dMnO3 has been successfully prepared by means of solid state reaction at high temperature. Its crystal structure, as well as those of Cr-doped samples (Ho1−xCax)(Mn1−yCry)O3, has been refined by the Rietveld method, using X-ray powder diffraction data. All the examined compounds crystallize in the Pnma space group with a distorted perovskite-type structure. The distortion of the BO6 octahedra, due to the Jahn–Teller Mn3+ ionic species, decreases with the Cr content. Bond valence sum calculations were carried out using the refined results
New insights into the magnetic properties of LaErO3, (La0.5Er0.5)2O3 and (La0.5Dy0.5)2O3 oxides
No full textOrthorhombic LaErO3 and cubic (La0.5 Ln 0.5)2O3 oxides (Ln: Er, Dy) were examined by neutron powder diffraction between 1.5 K and 15 K in order to investigate their crystallographic and magnetic structures. At 1.5 K both LaErO3 and (La0.5Er0.5)2O3 display a magnetic moments ordering, whereas for (La0.5Dy0.5)2O3 only short range magnetic correlations can be argued, suggesting a possible magnetic moments ordering at lower temperature. LaErO3 is characterized by a magnetic wavevector k = (0, 0, 0) and forms an antiferromagnetic G x C y A z-type structure belonging to the Shubnikov group with a total magnetic moment of 6.78(3) μ B. The antiferromagnetic structure of (La0.5Er0.5)2O3 is similar to the one typical of Er2O3, with a total magnetic moment of 4.28(2) μ B at both different magnetic sites; it is characterized by k = (0, 0, 0) and belongs to the magnetic Shubnikov group
Ferroelastic Transition and Local Structural Properties in Cs2NaBiCl6:Mn2+ Double Perovskites
No full textHalide double perovskites (DPs) have been extensively investigated for their optoelectronic properties, which make them suitable for optoelectronic applications such as solar cells and LEDs. The unique crystal structure of DPs can accommodate a wide range of transition metals, thereby enhancing their chemical diversity and properties. However, this also calls for in-depth studies to determine how the composition affects these materials. In this study, we comprehensively inspect the structural transitions of Cs2NaBiCl6:Mn2+ by synchrotron X-ray elastic scattering analysis at room temperature (290 K) and low temperature (10 K). Both X-ray powder diffraction and pair distribution function analysis indicate that the low-temperature polymorph crystallizes in the I4/m space group. The improper ferroelastic structural transition Fm3m -> I4/m is triggered by the condensation of the primary Gamma 4 + (T1g) soft mode, and spontaneous strain analysis reveals its second-order nature. The underlying dynamics are mainly determined by the cooperative tilting of the octahedral framework, whereas cationic positions appear fixed
Synthesis of ternary phases in the C-Mg-Ni system by combustion
No full textBy applying the combustion synthesis technique on stoichiometric elemental powder compacts and subsequent suitable isothermal annealing treatements, the following three crystalline compounds were prepared: MgxCyNi3, MgNi2(C), Mg2Ni(C). The samples were analyzed by means of X-ray and synchrotron powder diffraction and scanning electron microscopy, coupled with electronic microprobe analyses. Their electric and magnetic properties were investigated between 1.5 and 300 K
Cattaneo nel dibattito sullo stato dopo l'unificazione nazionale
No full textLa fortuna politica del pensiero federalista di Cattaneo dall'unificazione nazionale italiana alla prima guerra mondial
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