Search results for "Strontium"
showing 10 items of 195 documents
The electronic properties of SrTiO3-δ with oxygen vacancies or substitutions
2021
The authors would like to thank R. Dittmann for useful discussions, T. Kocourek, O. Pacherova, S. Cichon, V. Vetokhina, and P. Babor for their contributions to sample preparation and characterization. The authors (M.T., A.D.) acknowledge support from the Czech Science Foundation (Grant No. 19-09671S), the European Structural and Investment Funds and the Ministry of Education, Youth and Sports of the Czech Republic through Programme “Research, Development and Education” (Project No. SOLID21 CZ.02.1.01/0.0/0.0/16-019/0000760). This study was partly supported by FLAG-ERA JTC project To2Dox (L.R. and E.K.). Calculations have been performed on the LASC Cluster in the Institute of Solid State Phy…
First principles studies of the self trapped hole and the fluorine adsorption on the SrF2(111) surface
2013
Abstract By using density functional theory (DFT) with hybrid exchange potentials, namely DFT-B3PW, the ground states of self trapped hole and adsorbed fluorine atom on the strontium fluoride (1 1 1) surface are investigated. The self trapped hole at an interstitial anion site is denoted by H-center. In both the H-center and fluorine adsorption cases, the strong relaxations due to the surface effects are observed. In the H-center case, the unpaired electron distributes almost equally over two H-center atoms. This equivalent distribution of the unpaired electron is totally different from that of the bulk H-center [J. Phys. Chem. A 114 (2010) 8444]. The other case with an adsorbed fluorine at…
The use of tree-rings and foliage as an archive of volcanogenic cation deposition.
2007
Tree cores (Pinus nigra ssp. laricio) and leaves (Castanea sativa) from the flanks of Mount Etna, Sicily were analysed by ICP-MS to investigate whether volcanogenic cations within plant material provide an archive of a volcano's temporal and spatial depositional influence. There is significant compositional variability both within and between trees, but no systematic dendrochemical correlation with periods of effusive, explosive or increased degassing activity. Dendrochemistry does not provide a record of persistent but fluctuating volcanic activity. Foliar levels of bioaccumulated cations correspond to modelled plume transport patterns, and map short-term volcanic fumigation. Around the fl…
Local dynamics and phase transition in quantum paraelectric SrTiO3 studied by Ti K-edge x-ray absorption spectroscopy
2016
Strontium titanate is a model quantum paraelectric in which, in the region of dominating quantum statistics, the ferroelectric instability is inhibited due to nearly complete compensation of the harmonic contribution into ferroelectric soft mode frequency by the zero- point motion contribution. The enhancement of atomic masses by the substitution of 16 O with 18O decreases the zero-point atomic motion, and low-T ferroelectricity in SrTi18O3 is realized. In this study we report on the local structure of Ti in SrTi16O3 and SrTi18O3 investigated by Extended X-ray Absorption Fine Structure measurements in the temperature range 6 - 300 K.
NanoSr - A New Carbonate Microanalytical Reference Material for In Situ Strontium Isotope Analysis
2019
The in situ measurement of Sr isotopes in carbonates by MC‐ICP‐MS is limited by the availability of suitable microanalytical reference materials (RMs), which match the samples of interest. Whereas several well‐characterised carbonate reference materials for Sr mass fractions > 1000 µg g−1 are available, there is a lack of well‐characterised carbonate microanalytical RMs with lower Sr mass fractions. Here, we present a new synthetic carbonate nanopowder RM with a Sr mass fraction of ca. 500 µg g−1 suitable for microanalytical Sr isotope research (‘NanoSr’). NanoSr was analysed by both solution‐based and in situ techniques. Element mass fractions were determined using EPMA (Ca mass fraction),…
Preservation of successive diagenetic stages in Middle Triassic bonebeds: Evidence from in situ trace element and strontium isotope analysis of verte…
2015
Abstract Bonebeds comprise reworked and time averaged constituents of different phosphatic vertebrate remains and, hence, provide an ideal substrate for the study of long and short term diagenetic processes. To test whether trace elements (U, Sr, REE) and 87 Sr/ 86 Sr ratios can be used for distinguishing between successive diagenetic signals, we performed geochemical analyses on vertebrate remains (bones, teeth, scales and coprolites) from two Triassic bonebeds located near Palzem (Germany). Trace element analysis was done on 170 vertebrate remains by LA-ICP-MS while 87 Sr/ 86 Sr ratios were determined for 39 bioclasts using LA-MC-ICP-MS. Although a low inter- and intra-bioclast REE variab…
New Family of Ruddlesden−Popper Strontium Niobium Oxynitrides: (SrO)(SrNbO2-xN)n (n = 1, 2)
2002
The new family (SrO)(SrNbO2-xN)n (n = 1, n = 2) constitutes the first example of strontium niobium Ruddlesden−Popper oxynitrides and provides layered structures to obtain mixed valence niobium comp...
(Table 1) Trace element/Ca ratios of Orbulina universa shells from late Neogene Mediterranean samples
2008
A Mediterranean composite sedimentary record was analyzed for Ba/Ca ratios on carbonate shells of Orbulina universa planktonic foraminifer (Ba/Ca)carb providing the opportunity to study and assess the extent of freshwater inputs on the basin and possible impacts on its dynamics during the Tortonian to Recent period. A number of scanning electron microscope analyses and auxiliary trace element measurements (Mn, Sr, and Mg), obtained from the same samples, exclude important diagenetic effects on the studied biogenic carbonates and corroborate the reliability of (Ba/Ca)carb ratios in foraminifera calcite as indicators of seawater source components during the studied interval. A long-term trend…
Water vapour pressure above saturated salt solutions at low temperatures
1999
Abstract The properties of water–salt systems in relation to their vapour pressure are studied especially at low temperature. The water vapour pressure of saturated salt solutions of strontium chloride, zinc chloride, nickel chloride, nickel nitrate, magnesium chloride, magnesium bromide, magnesium nitrate, calcium chloride, potassium nitrite, lithium chloride, lithium bromide, lithium iodide and sodium bromide are measured in a temperature range −40 to +10°C. The apparatus used in this study, is well adapted to measure very low pressure with an uncertainty of pressure measurement of 2% for a range between 10−3 and 10 mm Hg. The experimental values are fitted by Antoine equation with mean p…
Mixed complexes of alkaline earth uranyl cabonates: A laser-induced time-resolved fluorescence spectroscopic study
2008
The interaction of the alkaline earth ions Mg2+, Sr2+ and Ba2+ with the uranyl tricarbonate complex has been studied by time resolved laser-induced fluorescence spectroscopy. In contrast to the non-luminescent uranyl tricarbonate complex the formed products show slight luminescence properties. These have been used to determine the stoichiometry and complex stabilities of the formed compounds. As the alkaline earth elements are located in an outer shell of the complex the influence of the type of the alkaline earth element on the stability constant is not very drastic. Therefore all obtained data were averaged in order to derive an common stability constant for the described complexes. These…