Strontium composition

Rathburn A. E. and Deckker P. D. (1997) Magnesium and strontium compositions of recent benthic foraminifera from the Coral Sea, Australia and Prydz Bay, Antarctica. Mar. Micropaleontol. 32, 231-248. 

GPC (total radioactive strontium) = beta gas proportional counter Bq = Becquerel dpm = disintegrations per minute EDTA = ethylenediamine tetraacetic acid GFAAS (total strontium) = graphite furnace atomic absorption spectroscopy ICP-AES (total strontium) = inductively coupled plasma atomic emission spectroscopy ICP-MS (isotopic strontium composition) = inductively coupled plasma-mass spectrometry LSC (isotopic quanitification of 89Srand 90Sr) = liquid scintillation counting pCi = pico curies (10-12 curies) PIXE (total strontium) = proton induced x-ray emission TMAH = tetramethylammonium hydroxide TNA (total strontium) = thermal neutron activation and radiometric measurement TRXF (total strontium) = total-reflection x-ray fluorescence... 

Bismuth trioxide forms numerous, complex, mixed oxides of varying composition when fused with CaO, SrO, BaO, and PbO. If high purity bismuth, lead, and copper oxides and strontium and calcium carbonates are mixed together with metal ratios Bi Pb Sn Ca Cu = 1.9 0.4 2 2 3 or 1.95 0.6 2 2 3 and calcined at 800—835°C, the resulting materials have the nominal composition Bi PbQ4Sr2Ca2Cu20 and Bi 25PbQgSr2Ca2Cu20 and become superconducting at about 110 K (25). 

Historically, materials based on doped barium titanate were used to achieve dielectric constants as high as 2,000 to 10,000. The high dielectric constants result from ionic polarization and the stress enhancement of k associated with the fine-grain size of the material. The specific dielectric properties are obtained through compositional modifications, ie, the inclusion of various additives at different doping levels. For example, additions of strontium titanate to barium titanate shift the Curie point, the temperature at which the ferroelectric to paraelectric phase transition occurs and the maximum dielectric constant is typically observed, to lower temperature as shown in Figure 1 (2). 

Fig. 1. Effect of compositional variations on the dielectric properties of strontium titanate-barium titanate solid solutions. A, BaQ SrQ QTiO B,...

The anode material in SOF(7s is a cermet (rnetal/cerarnic composite material) of 30 to 40 percent nickel in zirconia, and the cathode is lanthanum rnanganite doped with calcium oxide or strontium oxide. Both of these materials are porous and mixed ionic/electronic conductors. The bipolar separator typically is doped lanthanum chromite, but a metal can be used in cells operating below 1073 K (1472°F). The bipolar plate materials are dense and electronically conductive. 

Thermogravimetry may be used to determine the composition of binary mixtures. If each component possesses a characteristic unique pyrolysis curve, then a resultant curve for the mixture will afford a basis for the determination of its composition. In such an automatic gravimetric determination the initial weight of the sample need not be known. A simple example is given by the automatic determination of a mixture of calcium and strontium as their carbonates. 

Recognition among bone-chemistry researchers that strontium enters bone in proportion to dietary levels has resulted in widely accepted yet erroneous inferences about the relationships among various elements in bone and past diet. One such inference is that more of any element in the diet translates directly to more of that element in bone. If an element is not biogenically incorporated within bone, or if biological levels are metabolically controlled, then that element will not reflect diet. A second erroneous inference is that strontium can be used to measure the dietary plant/meat ratio. Sr/Ca ratios in meat are generally lower than those of plants, but meat is also low in calcium and hence has little effect on the composition of bone. Plants, on the other hand, contribute substantially to bone composition. Variations in the strontium levels of bone thus more likely reflect differential consumption of plants rather than trophic position. Although efforts to determine plant/meat ratios from strontium and to draw dietary inferences from elements other than strontium and barium have not been successful, this failure has been due to inappropriate expectations, not to a failure of bone strontium to reflect diet. 

Strontium, that of Toots and Voorhies (1965), used these compositional differences among plants to assess not the dietary plant/meat ratio but the degree of browsing versus grazing. It is this phenomenon due to shifting plants that we are likely to observe in comparative Sr/Ca studies of bone, rather than the amount of meat in the diet, simply because plants have a much greater impact on diet composition. 

Strontium isotopes. Strontium isotopic compositions ( Sr/ Sr) of anhydrite, gypsum and barite from Kuroko deposits are summarized in Fig. 1.45 (Farrell et al., 1978 Honma and Shuto, 1979 Farrell and Holland, 1983 Yoneda et al., 1993 Yoneda and Shirahata, 1995). Sr/ Sr values of anhydrite and gypsum are slightly lower than that of seawater, suggesting that most of the strontium was derived from seawater, but a small amount of... 

Farrell, C.W., Holland, H.D. and Petersen, U. (1978) The isotopic composition of strontium in barites and anhydrites from Kuroko deposits. Mining Geology, 28, 281-291. 

Yoneda, T., Yin, S. and Shirahata, H. (1993) Strontium isotopic composition in barite from the Minamishiraoi Kuroko-type deposit. Southwestern Hokkaido, Japan. Resource Geology, 43, 427-434. 

Palmer MR, Edmond M (1992) Controls over the strontium isotope composition of river water. Geochim Cosmochim Acta 56 2099-2111... 

Strontium incorporated into the teeth, for example, becomes immobilized after formation of the teeth. The relative amounts of the isotopes of strontium in the teeth is, therefore, related to the average strontium isotope composition that an animal ingested in food or water while growing. Thus teeth retain a kind of record of both early exposure to the isotopes of strontium in the water and food ingested during their growing, early life. In the... 

Small TD, Warren LA, Roden EE, Ferris FG (1999) Sorption of strontium by bacteria, Fe(III) oxide, and bacteria-Fe(III) oxide composites. Environ Sci Technol 33 4465-4470... 

Ophel, I. L, and J.M. Judd. 1976. Strontium and calcium accumulation in fish as affected by food composition. Pages 221-225 in C.E. Cushing (ed.). Radioecology and Energy Resources. Proceedings of the Fourth National Symposium on Radioecology, 12-14 May 1975, Oregon State Univ., Corvallis, OR. Ecol. Soc. Amer., Spec. Publ. No. 1. 

A sample of a strontium titanium sulfide Sr TiS3 was found to have a unit cell in which the repeat distance of the T1S3 chains, cTis, was found to be 0.30 nm and that of the Sr chains, cSr, was found to be 0.54 nm (Fig. 4.38). It is found that 5.5 Sr units fit with 10 TiS3 units. What is (a) the composition and (b) the approximate unit cell c parameter Another preparation has a composition Srj i2TiS3. (c) What is the new approximate unit cell c parameter ... 

In addition to the chemical interactions described above, microstructural changes in the electrode can lead to performance degradation after long operation time. For example sintering of the porous structure can degrade electrode performance. In the case of LSM cathodes, the sintering ability is found to be related to the strontium dopant level and stoichiometric composition of (La, Sr)xMn03. In addition, LSM with A-site deficient compositions (x < 1) sinters more readily than their B-site deficient counterparts (x > 1) [198, 199],... 

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