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991.
Synthesis of starting materials for β-barium metaborate (β-BBO) crysal growth by a low-temperature “carbonate” method has been investigated. Materials systhesized below the σ-β phase transformation temperature of BBO have been subjected to thermogravimetry, X-ray difraction and chemical analysis. The results show that an almost carbonless stoichiometric β-phase can be obtained without the need for the widely employed high-temperature “carbonate” synthesis. Some advantages of using the β-BBO material synthesized by the low-temperature “carbonate” method are emphasized. 相似文献
992.
M. Lang A. Höhr H. Spille F. Steglich H. Rietschel G. Roth Y. Hidaka T. Murakami 《Zeitschrift für Physik B Condensed Matter》1989,74(1):3-4
We present results for the thermal expansion, (T), of both polycrystalline and single crystalline La2CuO4. Our results demonstrate the existence of an anomaly in (T) aroundT=35 K which is clearly intrinsic and most likely due to a lattice instability. 相似文献
993.
W. Wahl A. Birovljev T. Haninger D. Kucheida P. Roth 《Journal of Radioanalytical and Nuclear Chemistry》2002,252(2):255-259
In vivo skull measurements of 210Pb have been performed to assess the individual, chronic exposures of two persons living for 28 years in a house with a distinctly enhanced radon concentration of more than 10,000 Bq/m3. A partial body counter consisting of 4 HPGe detectors, which were placed close to parietal positions of the head, was used in the study. The lower limit of detection of 210Pb activity in the skeleton was found to be 40 Bq. Lead-210 activities of up to 152 Bq were found in the test persons, whereas no activity could be measured in an unexposed control person. The cumulative uptake of 210Pb into the body was assessed for each single test person by using the ICRP respiratory tract and the biokinetic models. A fairly good agreement (within a factor of 2) between in vivo measurements and model was achieved for these two test persons. The technique used in the study may be a useful tool to evaluate assumptions, which have to be made for the reconstruction of individual, cumulative exposures to high radon concentrations. 相似文献
994.
995.
996.
G. Roth G. Heger B. Renker J. Pannetier V. Caignaert M. Hervieu B. Raveau 《Zeitschrift für Physik B Condensed Matter》1988,71(1):43-52
Single crystal- and powder X-ray diffraction, powder neutron diffraction at room temperature and 3 K, high resolution electron microscopy and electron diffraction were used to study the crystal- and defect-structure of YBa2(Cu0.93Fe0.05)3O7. Crystals of this compound are superconducting (T
c
80 K) and appeart to be tetragonal down to at least 3 K. The structure resembles that of the undoped YBa2Cu3O7 phase with the oxygen content being very close to 7.0 and the Fe atoms preferentially occupying the Cu(1) site. A copper deficiency is shown to be present on this site too, leading to the approximate formula YBa2(Cu0.97Fe0.03)2(Cu0.86Fe0.10.04)O7. High resolution electron microscopy reveals the existence of orthorhombic micro-domains, 20–30 Å in diameter, probably due to short range ordering of oxygen atoms on the O(1) site. In view of these results the structure has to be regarded as being tetragonal only in a statistical sense. 相似文献
997.
998.
Reliable idealized structures for the β and γ forms of ZrO2·12Nb2O5 have been deduced following the observation of lattice images, recorded at a resolution of about 0.3 nm, from crystals oriented with their short b axes parallel to the incident electron beam. The structure of the β form is confirmed by preliminary results from single crystal X-ray studies. The present observations are compared with previous work on these phases. 相似文献
999.
1000.