Carol C. Phifer

The short-range structure of zinc polyphosphate glass

Abstract 31 P magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy and Raman spectroscopy have been used to examine the polyhedral arrangements in x ZnO · (1 − x )P 2 O 5 (0.50 ≤ x ≤ 0.71) glasses. The depolymerization of P metaphosphate chains by the addition of ZnO is quantitatively described by the increase in the concentration of Q 1 -phosphate sites, determined from the 31 P MAS-NMR spectra. When x > 0.60, the NMR and Raman spectra exhibit peaks due to Q 0 and Q 2 tetrahedra, indicating that structures disproportionate in glass melts near the pyrophosphate composition. The splitting of the Raman peak due to the Q 1 terminal oxygen stretching mode indicates that a variety of P-O-Zn bonds participate in the polyphosphate glass structure. The complex mixture of P and Zn polyhedra contributes to the glass-forming tendency of the high ZnO (> 60 mol%) compositions.

Effects of coordination environment on the Zr-F symmetric stretching frequency of fluorozirconate glasses, crystals, and melts

A treatment based on Badger’s rule is used to estimate symmetric stretching frequencies νs of the nonbridging fluorides of various ZrFn groups in the presence of divalent and monovalent countercations. New vibrational spectra of MgZrF6, Ba2ZrF8, and β‐BaZr2F10 are presented and incorporated into the method. The factors affecting νs are outlined and discussed in detail. Compilations of estimated frequencies are used to deduce the probable local structure around Zr ions in binary barium fluorozirconate glasses and in fluorozirconate melts containing lithium and sodium ions. It is concluded that the results of Raman spectroscopy indicate the presence of seven‐ and eight‐coordinate Zr in some barium fluorozirconate glasses.

Photobleaching Comparison of Poly(methylphenylsilylene) and Poly(phenylsilyne)

The effect of dimensionality on the photobleaching characteristics of Si-based polymers with phenyl substituents was investigated by studying the change in absorption upon exposure to 248- and 337‐nm excitation. Poly(methylphenylsilylene) was chosen as an archetype of the linear-chain polysilanes, and poly(phenylsilyne) was used as the comparable network polysilyne. Differences in bleaching behavior of the two types of polymers are explained in terms of Si–Si bonding and electronic interactions between the phenyl groups and the silicon frameworks. Wavelength-dependent effects include the degree of photodegradation of the phenyl rings and changes in polymer configuration due to photoscission and crosslinking. Absorption changes were accompanied by changes in the refractive index of the exposed regions of the samples. The refractive index modification was used to write embedded strip waveguides in the photosensitive thin films.

Polysilane-based thin films with high photosensitivity

The present work investigates the intrinsic photosensitivity of a family of poly(alkyl)(aryl)silanes and poly(hydridophenyl)silane for use in the development of photoimprinted waveguide devices. Limited testing of passive optical behavior (e.g. absorption, refractive index) and photosensitive response was performed for these materials in thin film form. It was determined that the materials exhibited dramatic photobleaching under 248 nm (KrF excimer laser) exposure. Based on a Kramers-Kronig analysis of the absorption changes, refractive index changes on the order of - 0.1 are estimated. Confirmation of this calculation has been provided via ellipsometry which estimates refractive index changes at 632 nm of -0.14 ± 0.01. In addition, embedded strips have been photoimprinted into the material to confirm waveguiding capacity of the films. Possible sources of photosensitivity in this material and its potential for application in various device configurations will be discussed.

The structure of barium zinc aluminate glasses

Abstract An alternative structural model is proposed for glasses in the BaOZnOAl 2 O 3 system. The original discovers of the glasses assumed that the zinc atoms are three-coordinate, a condition which is at variance with known crystal structures. The assumptions that zinc is four-coordinate, oxygen can be three-coordinate, and aluminum can be four- or five-coordinate form the basis for a more realistic description of the glass structure.