STUDY OF PHASES IN CRYSTALLINE SENTENCES

The objective of the study was to study the phases in the crystalline sentence of calcium molybdate with sodium metafanadat on the basis of phase equilibrium in binary sentence. For this sutyd, different mixtures are prepared based on different molar ratios and investigation is made about these different mixture physical properties. Finally, the study also draw a phase balanced chart for the studied substances. For methodology adopted, nine samples were prepared. The results shows that to form a solid solution as dissolving sodium metafandate in calcium molybdate up to 40% of sodium metafanadate and form a solid solution in this sentence confirms that the necessary conditions to form a soid solution. It is concluded that for difference less than 15%, unlimited solid solution is formed; whereas, for difference above 15%, limited solid solution is formed. Our conclusion also shows that these two elements solubility is limited where one possesses the characteristic of high electronegativity, while, the other possess the characteristic of low electro negativity.

Limited solid solution Li(Ni0,33Mn0,33Co0,33)1-xFexO2 with structure α-NAFEO2

In the framework of this work, the compositions Li (Ni0.33Mn0.33Co0.33)1-xFexO2 (0 ≤ x ≤ 1) of the tetrahedron LiNiO2-LiMnO2-LiCoO2-LiFeO2 were investigated. The samples were synthesized by the gel combustion method with starch. For the first time it was obtained without admixtures LiNi0.2Mn0.2Co0.2Fe0.4O2 solid solution with a layered crystalline structure a-NaFeO2, which can be used as a cathode material of lithium-ion batteries. An electrochemical testing of the homogeneous sample LiNi0.2Mn0.2Co0.2Fe0.4O2 and the sample with a minimum iron content LiNi0.3Mn0.3Co0.3Fe0.1O2 was conducted. The results show feasibility of further studying the homogeneity region and the properties of the solid solution Li (Ni, Mn, Co, Fe)O2.

Vacancy pairing and superstructure in the high-pressure silicate K1.5Mg2Si2O7H0.5: a new potential host for potassium in the deep Earth

The high-pressure silicate K1.5Mg2Si2O7H0.5, synthesized and characterized by Welchet al.[(2012),Am. Mineral.97, 1849–1857], has been re-examined with the aim of determining the nature of the superstructure noted in their study. The composition corresponds to a 1:1 combination of KMg2Si2O7H and K2Mg2Si2O7end-members, but it is not a solid solution. Single-crystal X-ray diffraction data for one of the original K1.5Mg2Si2O7H0.5crystals synthesized at 16 GPa/1573 K, has been collected using a much longer exposure time in order to improve the intensity statistics of weak superlattice reflections identified by Welchet al.(2012). The superstructure has been determined using a superspace approach as having the superspace groupCmcm(0,β,0)00sandt0= 1/16 with refined parametersa= 8.7623 (10),b= 5.0703 (7),c= 13.2505 (11) Å,V= 588.69 (12) Å3. This structure corresponds to one with the conventional space groupPbnmand unit-cell parametersa= 8.7623 (10),b= 20.281 (3),c= 13.2505 (11) Å,V= 2354.7 (5) Å3and is based upon a super-sheet motif in which ordering involves rows of pairs of vacant interlayer K sites. This is the third topologically distinct structure type for the KMg2Si2O7H−K2Mg2Si2O7join and suggests that there is very limited solid solution, and so it can be expected that each of the three structures (P63cm, P\bar 3 1m andPbnm) has its own stability field, rather than being part of a continuous compositional series based upon a single structure type. As such, K1.5Mg2Si2O7H0.5should be considered as a potentially significant host of K in the Earth's mantle.

Supergene iron sulpho-selenides from the Zapadno-Ozernoe copper-zinc massive sulphide deposit, South Urals, Russia: a new solid-solution series between pyrite FeS2 and dzharkenite FeSe2

Supergene Fe sulpho-selenides (pyrite, dzharkenite and their intermediate compositions) were discovered in the oxidation zone of the Zapadno-Ozernoe copper-zinc massive sulphide deposit, South Urals, in association with other rare supergene sulphides, such as galena, tetrahedrite, metacinnabarite, tiemannite, Pb sulpharsenides of the jordanite group, undetermined sulphosalts of Hg and Ag, and native elements, such as S, Au and Se. This is the second known occurrence of dzharkenite. The results of the investigation of Fe sulpho-selenides using electron microprobe analysis, X-ray diffraction (XRD) and reflected light microscopy show the existence of a limited solid-solution series between pyrite and dzharkenite, which has not been described before.

Apparent pyrrhotite-chalcopyrite solid solutions in charnockites: the Shevaroy Hills Massif, Tamil Nadu, S India and the Bamble Sector, SE Norway

Examples of apparent exsolution lamellae and lenticular blebs of chalcopyrite in pyrrhotite are described in orthopyroxene-bearing granulite facies rocks from two, oxidized (log10fO2 = −14 to −11), widely separated, well characterized high grade terranes: the Bamble Sector, SE Norway (795°C, 7.5 kbar) and the Shevaroy Hills Massif, Tamil Nadu, S India (750°C, 7.5 kbar). These exsolution features only occur in isolated pyrrhotite grains and not in integral pyrrhotite-pyrite-chalcopyrite-magnetite grain clusters which essentially represent an oxidation equilibrium. Reintegration of these chalcopyrite exsolution features back into the pyrrhotite host indicate Cu contents ranging from 1 to 5 wt.% in good agreement with experimental observations which indicate that pyrrhotite can take up to 7 wt.% Cu at temperatures above 800°C at pressures of ∼1 bar. This suggests that under high grade conditions these chalcopyrite exsolution features were in solid solution with pyrrhotite. Whether Cu stabilizes pyrrhotite at higher oxygen fugacities or these chalcopyrite-pyrrhotite grains represent a metastable phase is uncertain. One possibility is that the isolated pyrrhotite grains with chalcopyrite lamellae could represent grains that were preferentially not exposed to infiltrating fluids, which oxidized the pyrrhotites in other areas of the sample. A second possibility is that either these grains had enough Cu to stabilize them during pervasive infiltration of oxidizing fluids or that they represent a metastable phase with respect to the overall oxygen fugacity of the sample. The two conclusions that can be drawn from these observations are, firstly, that it is possible for pyrrhotite and chalcopyrite to form a limited solid solution at granulite facies temperatures and pressures under relatively high oxidizing conditions, i.e. 1.5 log units above fayalite-magnetite-quartz, at 800°C and 8 kbar. Secondly, this limited solid solution should have some bearing on the stability of pyrrhotite with respect to co-existing magnetite and pyrite as a function of the oxidation state of the rock, be it inherited or fluid induced.

The effect of excess bismuth on the ferroelectric properties of SrBi2Ta2O9 thin films

The effect of excess bismuth on the ferroelectric properties of SrBi2Ta2O9 (SBT) thin films having a perovskite-like layered structure was investigated for excess bismuth contents ranging from 0% to 100%. For the first time, a limited solid solution of SBT and Bi2O3 was shown to exist when the amount of excess Bi was less than 50%. The formation of a solid solution enhanced the grain size and a-b plane orientation of the films, resulting in substantial improvement in the ferroelectric hysteresis properties of the films. On the other hand, when the amount of excess Bi exceeded 50%, Bi2O3 appeared as a second phase which led to high leakage current and poor ferroelectric hysteresis curves. 30–50% excess Bi content was found to be the optimum composition with respect to grain size, crystallographic orientation, and single phase formation. Within this range, SBT films exhibit low leakage current density (˜10−9 A/cm2) and maximum remanent polarization (2Pr ˜12 µC/cm2).