Crystal structures and X-ray powder diffraction data for Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6 synthetic leucite analogues

Leucites are tetrahedrally coordinated silicate framework structures with some of the silicon framework cations partially replaced by divalent or trivalent cations. These structures have general formulae A2BSi5O12 and ACSi2O6; where A is a monovalent alkali metal cation, B is a divalent cation, and C is a trivalent cation. In this paper, we report the Rietveld refinements of three more synthetic leucite analogues with stoichiometries of Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6. Cs2NiSi5O12 is Ia $\bar{3}$ d cubic and is isostructural with Cs2CuSi5O12. RbGaSi2O6 is I41/a tetragonal and is isostructural with KGaSi2O6. CsGaSi2O6 is $I\bar{4}3d$ cubic and is isostructural with RbBSi2O6.

Formation of chromitite seams and associated anorthosites in layered intrusion by reactive volatile-rich fluid infiltration

Drilling related to development of the platinum-group element deposit of the J-M Reef of the Stillwater Complex returned samples of a rare chromitite seam between anorthosite and norite in a discordant anorthositic body. Plagioclase core An concentrations are marginally higher and modestly reversely zoned on the norite side (average Ancore = 83.8; average Ancore-Anrim = -1.1) as compared with the anorthosite side (Average Ancore 82.5; Average Ancore-Anrim = +1.0). The anorthosites are also characterized by a slightly smaller average plagioclase grain size than plagioclase in the norite (1.41 mm and 1.54 mm, respectively). The chromite can contain single and polyphase inclusions of orthopyroxene, plagioclase, amphibole, biotite and Cl-rich apatite. These and other compositional and textural features, as well as inference from other discordant anorthositic bodies in the Banded series, are all consistent with a chromatographic model of chromite precipitation at a reaction front as a norite protolith reacts with a Cl-rich aqueous fluid saturated in plagioclase alone. Chromitite seam formation is modeled using an infiltration metasomatic model, in which a fluid becomes progressively undersaturated in pyroxene as it rises into the hotter part of the crystal pile. As this pyroxene-undersaturated fluid moves through a noritic protolith, it dissolves the Cr-bearing orthopyroxene to produce an anorthosite. Chromite precipitates at the reaction front between the anorthosite and the norite owing to liberation of Mg and Cr from pyroxene. Continuous redissolution and reprecipitation of chromite occurs as the pyroxene dissolution front moves in direction of fluid flow, collecting the Cr lost from the anorthosite. Owing to Cr dissolved mainly as a neutral divalent cation complex, (CrCl(OH)0, in the solution, but incorporated as a trivalent cation in chromite, the required redox reaction can involve concurrent precipitation of sulfide with chromite. This mechanism differs from some recent models in that the anorthosites are themselves replacement bodies and are not original precipitates from a magma nor formed by loss of mafic material by partial melting. The results show the need for experimental mineral solubility data at T and P conditions appropriate to upper crustal mafic/ultramafic intrusions.

A high-Tc organic-ionic phase transition crystal obtained from a trivalent cation

The organic-ionic crystal of [1,4,7-triazacyclononammonium] Cl3, containing a trivalent cation, shows a high-temperature phase transition coupled with dielectric switching.

Copper Aluminum Spinels Doped with Cerium as Catalysts for NO Removal

Cu-Ce(Mn)-Al oxide catalysts to NO removal in the broad temperature range were synthesized and tested. The precursor of copper aluminium spinel was obtained with the coprecipitation method. By this method, Cu–Al spinels with various amounts of manganese and cerium were synthesized as well. These oxides crystallized in the structure of inverse spinel; however, Ce doping caused the appearance of additional CeO2 phase as determined by XRD. The samples were mesoporous solids with moderate surface area and porosity measured by low temperature sorption of nitrogen. The addition of another metal to Cu–Al spinel caused an increase of activity in selective catalytic reduction of nitrogen oxide with ammonia. The presence of manganese caused the formation of a higher amount of N2O by-product. The catalytic activity increased with the cerium concentration. For the sample with the atomic ratio Ce0.15Cu0.18, ca. 90% of NO conversion was registered between 200 and 350 °C. As examined with XPS spectroscopy, such conversion was attained due to the good dispersion of copper on the catalyst surface. This copper was placed mainly in spinel octahedral positions which enable its easier reduction. The spinel structure causes the presence of cerium as the trivalent cation important in redox cycles with the participation of copper.

Study of Structural and Magnetic Properties, Trivalent Cation Substitution of Cobalt base Spinel Ferrites CoCr0.04LaxFe1.96-xO4 (0 ≤ x ≤ 0.12)

In this research work a series of polycrystalline trivalent cation (Cr3+, La3+) substituted cobalt ferrite with general formula CoCr0.04LaxFe1.96-xO4 where 0.00 ≤ x ≤ 0.12 (in steps of 0.02) was synthesized using co-precipitation method and were sintered at 900°C for 6 hours. The phase identification and confirmation of the structure were confirmed employing the X-ray diffraction (XRD) and FTIR techniques. The size of crystallite was found on average, in the range of 53-106 nano-meters. FTIR results confirmed spinel ferrites structure. Moreover the morphological studies were observed through SEM. The elemental analysis of the samples was done by EDX while, I-V characterization of the represented sample was recorded using two probe method. The measured electrical resistivity of materials increased as dopant content increased. The magnetic behavior of the materials was studied using vibrating sample magnetometer (VSM). The saturation magnetization values and magnetic coercivity values decreased with the increase of La3+ concentration. The saturation magnetization (Ms) of the ferrite materials decreased with the reduction of size.

Hydroponic screening of traditional rice varieties in Assam, India to estimate their potential resistance to Al toxicity under P deficiency

Acid soils encompass nearly one-third of the available terrestrial land surface worldwide. Acidic soil is one of the major abiotic constraints for agricultural practices by potentially creating aluminum (Al) toxicity and/or phosphorous (P) deficiency. Assam, being an agricultural state of India, has the majority of its area covered by acidic soils due to the varied terrain in the region. Soil acidification increases the solubility of Al present in the soil from its nontoxic silicate or oxide forms into highly phytotoxic ionic Al (mainly the trivalent cation Al³⁺). Ionic Al can form complexes with the available phosphorous leading to plant nutrient deficiency. In the present investigation, screening of traditional rice varieties from Assam was conducted for tolerance to combined Al toxicity and P deficiency. Seedlings of 41 rice landraces from various agro-climatic locations were subjected to three different concentrations of Al (0, 50, 100 µM) for 24, 48, and 72 h under P deficiency in static nutrient culture to identify the extent of their resistance to these stressed conditions. Different morpho-physiological parameters (root and shoot lengths, fresh and dry weight yields, chlorophyll and relative water content) were evaluated after stress treatment. All the experiments were conducted in a randomized block design with three replicates. Based on the overall morphological characters, total stress response index (TSRI) was calculated which showed a variation ranging from 18 to 23. Accordingly, the varieties were classified into different groups of resistance. Varieties ‘Moti’ and ‘Baismuthi’ were found to be the least resistant, whereas ‘Holpuna’, ‘Beto’, and ‘Soria Sali’ were identified as most tolerant varieties to Al toxicity under P deficiency. The findings of the present investigation could be exploited for developing promising varieties in future rice breeding programs.