Thermal equilibrium of Ge-related defects in a GeO2-SiO2 glass
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In a 15.7 GeO2⋅84.3 SiO2 glass prepared by a vapor axial deposition method, optical absorptions at 4.92 and 5.08 eV were observed from 300 to 600 K. The results were then compared with electron spin resonance (ESR) measurement using the same samples. The absorption at 4.92 eV was found to increase with increasing temperature, while the optical absorption at 5.08 eV decreased with increasing temperature. These changes of optical absorption indicate that the concentration of neutral oxygen monovacancy is reduced at higher temperatures. The changes were quite reversible with the temperature. Concentration of Ge E′ center, estimated from ESR, increased with increasing temperature, which is in contrast with the decrease of neutral oxygen monovacancy. The present result strongly suggests the thermal equilibrium reaction between neutral oxygen monovacancy and Ge E′ center.Keywords:
Thermal equilibrium
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Abstract Umsetzung von Li‐,Gen‐Einkristallen mit Benzophenon in THF führt unter strger topotaktischer Entmetallierung (Bildung von Li" und den Radikalanionen von PhzCO) zu Einkristallen der neuen Germanium‐Modifikation allo‐Ge.
Germanium compounds
Metastability
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High-temperature x-ray diffraction patterns of germanium plus germanium oxide GeO2 between 750° and 1400°C, showed that germanium monoxide GeO is not a stable compound. At elevated temperatures germanium can dissolve up to 60 atom percent of oxygen. The oxygen causes first a slight expansion and then a contraction of the Ge lattice. At 850° and 930°C, the x-ray pattern of a germanium-oxygen compound, consisting of equimolecular quantities of germanium and oxygen, showed only the germanium pattern. At 1000° and higher (above the melting point of pure germanium, 965°C), the germanium pattern disappears, and liquid-like structure is visible, though the sample is still solid (melting point 1430°C). When the temperature is lowered again to 930°C, the germanium pattern reappears. The electrical resistivity of the Ge and GeO2 mixture shows a sharp break at 970°C. In the germanium-oxygen compound we thus have a disordering of the germanium lattice above the melting point of pure germanium.
Germanium oxide
Germanium compounds
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Valency
Germanium compounds
Isotopes of germanium
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Photoexcitation
Pulsed EPR
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Solid-state physics
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The significance of reducing iron and other impurities and increasing germanium grade is introduced,and the reasons of high iron in germanium concentrate are analyzed.The effective measures for reducing impurities in germanium concentrate have been taken;iron content in germanium concentrate is reduced greatly and germanium content is increased.
Germanium compounds
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New thermally detected electron paramagnetic resonance (TD-EPR) experiments at 35 GHz including photoinduced effects, are described. The resonances are attributed to a V2+ (II) centre with a 4T1 ground state as before. In order to attempt to identify the nature of the centre, a trigonal model is presented which supposes that the V2+ ion is part of a complex in which one of the neighbouring As ions is replaced by a defect. It is shown that the TD-EPR results are consistent with such a model but this does not prove by itself that the V2+(II) ion is part of a complex. Other experimental results obtained by other techniques are also discussed and related to the TD-EPR data obtained here. After consideration of all the available data, the most probable conclusion is that V2+ (II) is part of a complex.
Trigonal crystal system
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