# ALBERT

## All Library Books, journals and Electronic Records Telegrafenberg

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• 1
Electronic Resource
s.l. ; Stafa-Zurich, Switzerland
Materials science forum Vol. 10-12 (Jan. 1986), p. 833-838
ISSN: 1662-9752
Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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• 2
Electronic Resource
Springer
Journal of materials science 24 (1989), S. 83-87
ISSN: 1573-4803
Source: Springer Online Journal Archives 1860-2000
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes: Abstract Single-phase copper manganite spinels Cu x Mn3−x O4 with 0⩽x⩽1 were prepared by a careful thermal processing of copper-manganese co-precipitated hydroxide precursors. Powder X-ray diffraction (XRD) analysis of these spinels revealed the presence of a tetragonally distorted single spinel phase, with tetragonal distortionc/a 〉 1 which decreases with copper content. Thermogravimetric analysis (TGA) curves, run in an oxygen atmosphere for all the compositions studied, are characterized by a stability step up to 250 to 300° C, followed by a domain of oxidation between 300 and 900° C and finally a domain of reduction that restores the initial stoichiometry of the samples. The oxidation is observed to occur in two successive steps. The phenomenon appearing at the low temperature is due to the oxidation of Cu+ ions, while that at higher temperature corresponds to the oxidation of Mn2+ ions in tetrahedral sites. Further, electrical resistivity measurements confirm the presence of Cu+ ions on the tetrahedral sublattice of spinel. Correlation of the results obtained by XRD, TGA and electrical resistivity measurements permits one to infer the cation distribution, given by Cu x + Mn 1−x 2+ [Mn 2−x 3+ Mn x 4+ ] O 4 2− .
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• 3
Electronic Resource
Springer
Journal of materials science 25 (1990), S. 4410-4414
ISSN: 1573-4803
Source: Springer Online Journal Archives 1860-2000
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes: Abstract Single-phase nickel manganite spinels, Ni x Mn3−x O4, with 0.5 ⩽x ⩽ 1, were prepared by a careful thermal processing of nickel-manganese coprecipitated oxalate precursors. Powder X-ray diffraction analysis of the spinel revealed the presence of cubic single spinel phase with parametera which decreases with nickel content. The lattice parameter variation can be explained in terms of the distribution of Ni2+ ions on the octahedral sites. Therefore, a fine analysis of data shows that some Ni2+ ions (forx〉0.56) are located in tetrahedral sites. The percentage of nickel in A-sites increases with nickel content (x) following the relation % Ni2+ in A sites =P = − 82.1x 2+192.4x−81.5 and thus the general formula for cation distribution is $${\text{Mn}}_{{\text{1 - }}y}^{{\text{2 + }}} {\text{Ni}}_y^{{\text{2 + }}} [{\text{Ni}}_{x{\text{ - }}y}^{{\text{2 + }}} {\text{Mn}}_{{\text{2 - 2(}}x - y)}^{{\text{3 + }}} {\text{Mn}}_{x{\text{ - }}y}^{{\text{4 + }}} ]{\text{O}}_{\text{4}}^{{\text{2 - }}}$$ withy=xP/100 This relationship explains the electrical properties of semiconducting nickel manganite ceramics.
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• 4
Electronic Resource
Springer
Journal of materials science 27 (1992), S. 2397-2405
ISSN: 1573-4803
Source: Springer Online Journal Archives 1860-2000
Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes: Abstract Liquid-phase sintering (LPS) of ceramics issued from powders of bismuth-titanium-doped zinc oxide, made of spherical grains constituted of small crystallites, were studied by dilatometry. A correlation can be established between the shape of the shrinkage curves and the microstructure of the ceramics. During sintering the spherical grains are destroyed as soon as the liquid phase appears and the rearrangement proceeds directly between crystallites. Systematic studies were carried out on bismuth-titanium-doped ZnO. For small Bi contents, the beginning of a solid-phase sintering process occurs. For 1 at % Bi in the binary system Bi-doped ZnO, rapid shrinkage leads to a well-densified ceramic with a grain size of 70 μm on average. The influence of the amount of titanium iny% Ti-1% Bi-doped ZnO is discussed. Whatever the amount of Ti, LPS is observed. The shrinkage curves depend greatly on the amount of Ti: only a Ti content ofy=0.6 % leads to an increase in grain size (100 μm on average).
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• 5
Electronic Resource
Springer
ISSN: 1572-9729
Source: Springer Online Journal Archives 1860-2000
Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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• 6
Electronic Resource
Woodbury, NY : American Institute of Physics (AIP)
Applied Physics Letters 67 (1995), S. 3390-3392
ISSN: 1077-3118
Source: AIP Digital Archive
Topics: Physics
Notes: Highly accurate layer thicknesses are required for multilayers involved in photonic devices, such as Bragg reflectors. In this letter, we demonstrate that precise, real-time monitoring of molecular beam epitaxy growing layers can be achieved by near-normal incidence dynamic reflectometry with a tunable sapphire–titanium laser used as a source. The advantage of this new technique lies in the possibility of synchronizing the material changes and the reflectivity extrema by selecting adequate analysis wavelengths. This technique is shown to provide 885 nm GaAs–AlAs Bragg reflectors with a layer thickness accuracy in excess of 1%. © 1995 American Institute of Physics.
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• 7
Electronic Resource
Woodbury, NY : American Institute of Physics (AIP)
Applied Physics Letters 67 (1995), S. 244-246
ISSN: 1077-3118
Source: AIP Digital Archive
Topics: Physics
Notes: In situ molecular beam epitaxy control of III–V optoelectronic device growth has been achieved by dynamic optical reflectometry with tunable excitation wavelength, through the use of a titanium:sapphire laser light source. This new multiwavelength reflectometry method was used to determine the values of the AlAs and GaAs refractive indices at growth temperature (600 °C). Index dispersion between 760 and 960 nm is presented and found to be in good agreement with the existing models. © 1995 American Institute of Physics.
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• 8
Electronic Resource
Woodbury, NY : American Institute of Physics (AIP)
Applied Physics Letters 59 (1991), S. 152-154
ISSN: 1077-3118
Source: AIP Digital Archive
Topics: Physics
Notes: Molecular beam epitaxy of Nd3+-doped CaF2 monocrystalline layers on CaF2 substrates is demonstrated. Nd concentration is controlled by the temperature of an evaporation cell containing NdF3. Photoluminescence spectra of the samples show emissions from Nd3+ centers in tetragonal symmetry sites as a consequence of the charge compensation mechanism provided by interstitial F− ions.
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• 9
Electronic Resource
[S.l.] : American Institute of Physics (AIP)
Journal of Applied Physics 76 (1994), S. 270-273
ISSN: 1089-7550
Source: AIP Digital Archive
Topics: Physics
Notes: CaF2:Er layers have been grown by molecular-beam epitaxy on (100)-oriented CaF2 substrates; the Er concentration ranges from 1% to 50% (mole fraction). The 1.54 μm emission observed under excitation around 800 nm was studied by photoluminescence. Up to 35% Er concentration the integrated emission increases monotonously, quenching appearing for higher doping levels. Photoluminescence results are discussed within the framework of previous studies of Er3+ emission in the near-infrared range (830–860 nm) in order to gain insight into the Er centers involved in the 1.54 μm emission.
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• 10
Electronic Resource
[S.l.] : American Institute of Physics (AIP)
Journal of Applied Physics 81 (1997), S. 679-684
ISSN: 1089-7550
Source: AIP Digital Archive
Topics: Physics
Notes: Yb:Er: codoped CaF2 monocrystalline films have been grown by molecular beam epitaxy (MBE) using YbF3, ErF3, and CaF2 evaporation on CaF2 substrates. Luminescence and excitation of luminescence at 25 K are measured in order to investigate the role of Yb3+ codoping and the effect of the growth conditions during the MBE process on the incorporation of active rare-earth species in CaF2. It is found, from a comparison with earlier work on singly doped thin films, that the energies of the levels of Er3+ ions are not modified by the double doping, whereas mixed complex centers are formed. Growth conditions are found to be important controlling factors for the incorporation of Yb3+ as a sensitizer, and, consequently, for the transfer efficiency. From excitation and absorption spectra it is shown that the lowest component of the Er:4I11/2 manifold has an energy higher than that of Yb:2F5/2 and the consequences are discussed. © 1997 American Institute of Physics.
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