Reduction of vanadium ions in 50 mol% vanadium germanate glass under the influence of annealing the sample in air was studied by Auger and X-ray photoelectron spectroscopy. It was concluded that V5+ reduces mostly to V3+ and to a small extent to V4+. The same conclusion was drawn from optical absorption data.

X-ray photoelectron spectroscopy study of vanadium germanate glass

Recent measurements on the V2O5-GeO2 glass system consisting of an equimolar mixture of V2O5 and GeO2 revealed that increase in electrical conductivity of these glasses upon annealing could be attributed to the increase in V4+ and V3+ content which accompanied the microstructure formation. In the present work we report a similar study on V2O5-TeO2 and V2O5-P2O5 glass systems. It was found that in tellurite glass V3+ content increased upon annealing and V4+ content remained unchanged. In phosphate glass some increase in V4+ and no significant change in V3+ contents were observed. V3+ and V4+ contents in glasses could be best estimated from optical and electron paramagnetic resonance spectra, respectively.

Spectroscopic, electrical and EPR studies of binary semiconducting oxide glasses containing 50 mol% V2O5

Various transition metal oxides, such as TiO2, V2O5, NiO, CuO, and ZnO are added to germanium-tellurite glass and measurements are reported of the electrical conductivity, density, optical absorption, infra-red absorption spectra, and electron spin resonance. It is found that the d.c. conductivity of glasses containing the same amount of V2O5 is higher than that of germanium tellurite glasses containing a similar amount of other transition metal oxides, and is due to hopping between localized states. The optical absorption measurements show that the fundamental absorption edge is a function of glass composition and the optical absorption is due to forbidden indirect transitions. From the infra-red absorption spectra, it is found that the addition of transition metal oxides does not introduce any new absorption band in the infra-red spectrum of germanium tellurite glasses. A small shift of existing absorptions toward higher wave number is observed. The ESR measurements revealed that some transition metal ions are diamagnetic while others are paramagnetic in the glass network.



Quelques oxydes des metaux transitionnels comme TiO2, V2O5, NiO, CuO et ZnO etaient introduits dans les verres du tellurite de germanium, et les resultats des mesures de la conductibilite elec-trique, du densite, du spectre d'absorption optique et d'absorption infra-rouge, et de la resonance electronique paramagnetique (EPR) sont presentes. On etablit que la conductibilite directe des verres avec V2O5 est plus grande que dans les verres du tellurite de germanium avec la měne contenu d'autre oxyde du metal transitionnel, et est une consequence d'un processus electronique de “hopping” entre les etats electroniques localises. Les resultats pour l'absorption optique montrent que la limite fundamentale d'absorption est une fonction de la composition du verre et l'absorption optique est associee avec les transitions non-directes. L'absorption spectrale infra-rouge indiquent que l'addition des oxydes metalliques transitionnels n'introduit pas les bandes d'absorption nouvel-les dans le verre du tellurite de germanium. Une petite deplacement des absorptions bien connues ver les energies plus petites est observee. Les mesures de EPR indiquent que quelques metaux transitionnels sont diamagnetiques et les autres sont paramagnetiques dans le verre.

The electronic and optical properties of germanium tellurite glasses containing various transition metal oxides

The infrared spectra. X-ray diffraction and electrical conductivity of sodium tetraborate glasses containing nickel have been studied as a function of nickel oxide content. It was found that addition of nickel oxide does not seem to introduce any new absorption band as compared with the infrared spectrum of pure sodium tetraborate glass. The electrical conductivity measurements revealed that the activation energy for conductivity increases with nickel oxide content. This could be explained on the basis of the concept of Hubbard bands, and possibly by a block effect of the nickel ion on the overall mobility of the sodium ion. Measurements were made on unannealed samples and some samples annealed at different temperatures. Annealing the samples at temperatures in the range 460 to 480° C causes the appearance of a crystalline phase, resulting in an increase of electronic conductivity.

Spectroscopic and electrical studies of sodium tetraborate glasses containing nickel oxide

Mesure des spectres d'absorption IR et etude de la cristallisation afin d'etudier la coordination des ions Ti 4+ dans les verres TiO 2 −GeO 2 , le changement eventuel de coordination des ions Ge 4+ par addition de TiO 2 et l'influence du traitement thermique sur les parametres decrivant la cristallisation

Infrared and X-ray diffraction studies of TiO2−GeO2 glasses

The DC conductivity of semiconducting vanadium germanate glasses of compositions in the range of 40-70 mol(%)V2O5has been measured in the temperature region 300-530 K. Measurements have been made on unannealed samples and some samples annealed at 300°C. Annealing the samples at temperatures of about 300°C causes the appearance of a crystalline phase resulting in an increase of conductivity. The crystalline temperature has been estimated from the conductivity data for unannealed samples. These seem to be in reasonable agreement with the corresponding results found in the literature.

Electrical conductivity of semiconducting V2O5-GeO2glasses

A series of glass samples was prepared from mixtures of GeO2 TiO2, and Na2Co, (for Na2O). Measurements were made of the DC conductivity as a function of composition and temperature. TheBe results are interpreted in terms of the activation energy which decreased linearly with the TiO2, content of the glasses. Capacitance measurements showed that one effect of increasing the TiO2, content was to increase the permittivity. Some measurements at high electric fields were made and the evidence for small polarons is reported.

Some electrical properties of sodium-titanium-germanate glasses

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Electrical conductivity of semiconducting V2O5-GeO2glasses

Some electrical properties of sodium-titanium-germanate glasses