12035-89-1Relevant academic research and scientific papers
Thermodynamic properties of silicate glasses and melts: II. System SrO-SiO2
Lopatin,Shugurov,Stolyarova,Tyurnina
, p. 1878 - 1884 (2006)
High-temperature mass spectrometry was used to determine the Gibbs energies, activities, and chemical potentials of SrO and SiO2 in glasses and melts of the SrO-SiO2 system in the temperature range 1840-1970 K. Negative deviations fr
Non-isothermal decomposition kinetics of alkaline earth metal carbonates
Maitra,Bandyopadhyay,Das,Pal,Pramanik
, p. 1299 - 1303 (2007)
The kinetics of thermal decomposition of four synthetic alkaline earth metal carbonates (MgCO3, CaCO3, SrCO3, and BaCO3) was studied under non-isothermal conditions using thermogravimetry. The activation energy and the pre-exponential factor for the decomposition reactions were determined using the Agarwal and Sivasubramanium integral approximation method. A new method was developed using a Turbo-C-based computer program to evaluate the integral of the kinetic equation. It was observed that the decomposition reaction of MgCO3 and CaCO 3 followed two-dimensional diffusion-controlled kinetics and the decomposition reaction of SrCO3 and BaCO3 followed a Ginstling-Brounshtein model-based diffusion-controlled kinetics.
Oxidative Dimerisation of Methane over BaCO3, SrCO3 and these Catalysts promoted with Alkali
Aika, Ken-ichi,Moriyama, Takeshi,Takasaki, Nobuhiro,Iwamatsu, Eiji
, p. 1210 - 1211 (1986)
The yield and selectivity for formation of C2 hydrocarbons from CH4 and O2 were 18.2 and 48.4 percent respectively over 2 g of BaCO3 at 1073 K at a CH4 : O2 ratio of 2.0 : 1, whereas the yield and selectivity were 2.5 and 99.5 percent over SrCO3 at 973 K at a CH4 : O2 ratio of 37.9 : 1.
EPR study of electron trapping on partially hydroxylated alkali-earth oxides occurring during SO2 disproportionation
Livraghi, Stefano,Paganini, Maria Cristina,Giamello, Elio
, p. 100 - 104 (2011)
We used the Electron Paramagnetic Resonance (EPR) technique to study the interaction of SO2 molecules on bare and partially hydroxylated alkali-earth oxide (AEO) surface. When SO2 is adsorbed on the surfaces of higher basicity (CaO and SrO) disproportionation reaction occurs with the formation of SO2- radical. We show also that, when the same reaction is present on partially hydroxylated surfaces a fraction of the electrons exchanged during the redox process are trapped on the oxide surface forming colour centres ((H+)(e-) centres).
A novel mixed valent chromium-layered oxide with peculiar magnetic properties: Sr4.5Cr2.5O9
Pelloquin,Wahl,Masset,Maignan,Michel,Raveau
, p. 375 - 383 (2000)
A new mixed valent chromium-layered oxide, Sr4.5Cr2.5O9, with a structure closely related to the '0201-1201' structure of the superconducting cuprate TIBa(2-x)La(2+x)Cu2O9, has been synthesized at normal pressure. This orthorhombic phase (a = 10.7 59(2) A, b = 5.4012(1) A, and c = 30.0755(6) A) consists of the regular intergrowth of [Sr2CrO4]0201 blocks and [(Sr0.5Cr0.5)Sr2CrO5]1201 blocks. It differs from the thallium cuprate by the 1:1 ordering of Sr and Cr species within the intermediate layer of the '1201' block, so that at this level CrO4 tetrahedra, containing Cr6+ species, are obtained. Moreover, at the boundary between the '1201' and '0201' blocks, CrO6 octahedra alternate with CrO5 pyramids, both occupied by Cr3+ species. The magnetic measurements show an original metamagnetic transition from an antiferromagnetic to a weak ferromagnetic state. These properties are interpreted in terms of strong intralaye and weak interlayer magnetic couplings between Cr3+ species through a superexchange mechanism. (C) 2000 Academic Press.
Crystal structures and magnetic properties of new europium melilites Eu2MSi2O7 (M = Mg, Mn) and their strontium analogues
Endo, Takashi,Doi, Yoshihiro,Wakeshima, Makoto,Hinatsu, Yukio
, p. 10809 - 10814 (2010)
Synthesis, crystal structures, and magnetic properties of melilite-type oxides A2MSi2O7 (A = Sr, Eu; M = Mg, Mn) were investigated. These compounds crystallize in the melilite structure with space group P421m. The 151Eu Moessbauer measurements show that the Eu ions are in the divalent state. The Eu2MgSi 2O7 is paramagnetic down to 1.8 K. Long-range antiferromagnetic ordering is observed at 3.4 K for Sr2MnSi 2O7. On the other hand, the Eu2MnSi 2O7 shows a ferrimagnetic transition at 10.7 K. From the magnetization and specific heat measurements, it is found that the Eu 2+ (14 μB) and Mn2+ (5 μB) sublattices order antiferromagnetically. This result indicates that an interaction between f-d electrons (Eu-Mn) predominantly operate in this compound.
The magnetoelectric perovskite Sr3Fe2TeO9: An insight from magnetic measurements and neutron powder diffraction
Ivanov,Nordblad,Eriksson,Tellgren,Rundl?f
, p. 776 - 789 (2007)
A study of the crystallographic and magnetic structures of the double perovskite Sr3Fe2TeO9 has been carried out on a polycrystalline sample using neutron powder diffraction (NPD) data between 10 and 650 K. An analysis of the NPD patterns at room temperature has shown that this compound crystallises in the tetragonal space group I4/m with a = 5.5614(7) ? and c = 7.867(1) ? and has a partially ordered arrangement of Fe and Te at the B-sites. The compound undergoes an I4/m → Fm-3m improper ferroelectric phase transition near 460 K. A low-temperature ferrimagnetic ordering (below TN = 260 K) has been followed from the magnetisation measurements and sequential NPD data analysis. In good agreement with magnetic measurements the ferrimagnetic structure with very weak magnetisation is defined by the propagation vector k = (0, 0, 0). In addition to the obtained experimental results on magnetic and electric properties some aspects of magnetoelectricity in this perovskite are also discussed and compared with those of another quaternary oxide Sr3Fe2B6+O9.
Reduction chemistry of platinum group metal perovskites
Wiley, John B.,Poeppelmeier, Kenneth R.
, p. 1201 - 1210 (1991)
The reduction chemistry of the perovskite and perovskite-related compounds, CaRuO3, SrRuO3, BaRuO3, SrIrO3, and BaIrO3, was examined. Samples were reduced at low temperatures (≤ 600°C) by direct reduction with hydrogen gas and by a method that utilized zirconium metal as an oxygen getter. No evidence for oxygen deficient perovskites was observed. In almost all cases, the mixed metal oxide was reduced to form the zero valent platinum group metal and the binary oxide or hydroxide (AO or A(OH)2). One exception was seen in the reduction of SrIrO3 via the getter method where the intermediate Sr4IrO6 was found.
Kinetics of free-surface decomposition of magnesium, strontium and barium carbonates analyzed thermogravimetrically by the third-law method
L'vov, Boris V.,Ugolkov, Valery L.
, p. 13 - 18 (2004)
The results of our thermogravimetric experiments on the decompositions of MgCO3, SrCO3 and BaCO3 powders and some data reported in the literature were used for the determination of the E parameter of the Arrhenius equation by the third-law method and estimation of the self-cooling effect on the results of these determinations. The experimental values of the E parameters for these carbonates (218, 286 and 302 kJ mol -1) are much higher than the enthalpies of equilibrium reactions (up to solid oxide and CO2) and the values accepted by TA community as the reference data. At the same time, these data are in a good agreement with the mechanism of congruent dissociative evaporation of carbonates with the simultaneous condensation of low-volatility oxides. Differences in the magnitudes of the τ parameter responsible for the consumption of condensation energy by the reactant are revealed. Instead of expected 0.50, the magnitudes of the τ parameter for Mg, Sr and Ba carbonates are as follows: 0.47, 0.42 and 0.10.
High-pressure synthesis and crystal structures of the strontium oxogallates Sr2Ga2O5 and Sr5Ga6O14
Kahlenberg, Volker,Goettgens, Valerie,Mair, Philipp,Schmidmair, Daniela
, p. 27 - 35 (2015)
Abstract High-pressure synthesis experiments in a piston-cylinder apparatus at 1.5 GPa/3.0 GPa and 1000°C resulted in the formation of single-crystals of Sr2Ga2O5 and Sr5Ga6O14, respectively. The structures of both compounds have been solved from single-crystal diffraction data sets using direct methods. The first compound is orthorhombic with space group type Pbca (a=10.0021(4) ?, b=9.601(4) ?, c=10.6700(4) ?, V=1024.6(4) ?3, Mr=394.68 u, Z=8, Dx=5.12 g/cm3) and belongs to the group of single layer gallates. Individual sheets are parallel to (0 0 1) and can be built from the condensation of unbranched vierer single chains running along [0 1 0]. The layers are characterized by the presence of four- and strongly elliptical eight-membered rings of corner connected tetrahedra in UUDD and UUUUDDDD conformation. Strontium atoms are sandwiched between the tetrahedral layers for charge compensation and are coordinated by six and seven oxygen ligands, respectively. Sr2Ga2O5 is isotypic with several other double sulfides and selenides. To the best of our knowledge, it is the first example of an oxide with this structure type. From a structural point of view, Sr5Ga6O14 is a phyllogallate as well. The crystal structure adopts the monoclinic space group P21/c (a=8.1426(3) ?, b=8.1803(3) ?, c=10.8755(4) ?, β=91.970(4)°V=723.98(5) ?3, Mr=1080.42 u, Z=2, Dx=4.96 g/cm3). Individual sheets extend along (0 0 1). Basic building units are unbranched dreier single chains parallel to [1 0 0]. The layers contain tertiary (Q3) und quaternary (Q4) connected [GaO4]-tetrahedra in the ratio 2:1 resulting in a Ga:O ratio of 3:7 and the formation of exclusively five-membered rings. Linkage between adjacent tetrahedral sheets is provided by three symmetrically independent strontium ions which are surrounded by six to eight oxygen atoms. The layers in Sr5Ga6O14 are similar to those observed in the melilite structure-type. Crystallochemical relationships between the present phases and other known compounds are discussed in detail.
