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Title:Structural characterization and optical transmission studies of vanadate glasses
Author(s):Anderson, Gordon Wood
Doctoral Committee Chair(s):Compton, W.D.
Department / Program:Physics
Subject(s):structural characterization
optical transmission
vanadate glasses
Abstract:Structural characterization and optical transmission studies have been carried out on vanadate glasses based on the system V205-P205 in the range 70.0-87.5 mole % V205 0 The optical studies are compared with other studies of crystalline V205, and additional transmission measurements on V20 S were performed. Structural characterization was carried out on samples initially containing 70.0, 80.0, and 87.5 mole % V205 by bright field, dark field, and diffraction electron microscopy. Replicas and powdered chips of bulk samples gave inconclusive results, and thinning techniques were not attempted due to the water solubility of the material. Blown, thin films were .used for study and indicated that any crystals occurring in the films were of dimension 20-40 R or less. Phase separation, possibly due to the spinodal mechanism, was observed in unannealed 87.5 mole % V205 films but not in unannealed films of other compositions. Annealing induced phase separation and growth probably due to nucleation and growth in the 70.0 mole % V 2 0 5 films. The same effect probablyqccurred in the 87.5 mole % V205 films. Heating at higher. temperatures induced crystallization in the 70.0 and 87.5 mole % V20 5 films, though it is not certain whether or not the induced phase separation proceeded directly to crystallization. The optical absorption of 70.0 and 87.S mole % V 2 0 S blown films of thickness about 1 to 2 was measured in the range 20 to 2S,000 cm- l at room and liquid nitrogen temperatures. Vibrational absorption peaks were observed atabcilit, 360, ,420, 680; 1010" and 1100 cm- l with additional structure likely at about 22S and 900 cm- l in the 70.0 mole % V20S films. Peaks were observed at about 330, 43S, 63S, 810, 1007, and 1085 cm- l with additional structure likely at about 21S cm- l in the 87. S mole % "films. ;;Noticeable temperature effects on spectra shape and peak positions were not observed. Absorption peaks were -1 also observed .at 1038 and 1277 cm in V20S at room temperature and at 91S, 1040, and 1274 cm- l and possibly at l2S6 cm- l at liquid nitrogen temperature. The peaks at about 1010 cm -1 in the glasses are thought to be the V-O stretching vibrations; the peaks at about 1090 cm- l are assigned to a phosphorous-oxygen vibration; and the peaks between 800-910 cm- l may be complex vanadium oxygen vibrations. Other peaks are unassigned. Between the fundamental absorption edge of the glasses in the short wavelength region of the visible and about 1300 cm- l a broad absorption tail was observed which is responsible for the dark black color of bulk samples. The cause of this absorption is not definitely ascertained, though V4+ ions are thought to contribute. The absorption edge of both the 70.0 and 87.5 mole % V20S glasses fits the condition for direct forbidden transitions as does the edge of V20So E values were determined to be 2.38 and 2.41 eV for 87.5 mole % g V20S films at room and liquid nitrogen temperatures, respectively, and 2.47 and 2.Sl eV for the 70.0 mole % V20S films at room and liquid nitrogen temperature respectively.
Issue Date:1969
Genre:Dissertation / Thesis
Rights Information:1969 Gordon Wood Anderson
Date Available in IDEALS:2011-07-12
Identifier in Online Catalog:6073756

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