Caroline S. Harris

Phase sensitivity of Raman spectroscopy analysis of CVD titania thin films

Photocatalytic titania thin films deposited on float glass by chemical vapor deposition were analyzed by transmission electron microscopy, atomic force microscopy, Raman spectroscopy, and X-ray diffraction. Raman spectroscopy results indicate its phase sensitivity in the presence of trace amount of anatase. This suggests a preferable method of using Raman spectroscopy to characterize mixed phases of titania thin films, especially when titania coatings are deposited on other crystalline oxide materials, for example, tin oxide.

Lithium ion conductors and proton conductors: Effects of plasticizers and hydration

Abstract Lithium ion conductors and proton conductors were developed in support of a large-area electrochromic transparency effort with the goal of identifying a polymer electrolyte that provides high ionic conductivity with good electrochemical and thermal stability. The best lithium ion conductor was found to be a transparent, solid uv -curable poly(alkyleneoxy)acrylate-LiCF 3 SO 3 complex that has excellent thermal stability, and room temperature ionic conductivity on the order of 10 −6 S cm −1 . The addition of 50 wt.% propylene carbonate to the polymer-salt complex increases its conductivity by three orders of magnitude, without degradation of its other physical properties. Two sulfonic acid-based polyelectrolytes were explored as potential proton conductors, a cross-linked poly(2-acrylamido-2-methyl-1-propane sulfonic acid), PAAMPS, which has practical use for temperatures up to about 70 °C, and a novel vinyl sulfonic acid/vinylpyrrolidone copolymer that has excellent thermal stability for over 1000 h at 90 °C. The copolymer has the potential for high conductivity based on its relatively low equivalent weight. Two different electrochromic devices containing the polymer electrolytes are described, and the temperature-dependent switching behavior of the devices is related to the conductivity of the polymer electrolytes.

A plasticized poly(alkyleneoxy)acrylate-based polymer electrolyte with high ionic conductivity

In this communication a highly conductive, plasticized polymer electrolyte, based on a UV-curable poly(alkyleneoxy)acrylate-LiCF,SO, complex, is described. This polymer electrolyte is a thermally stable transparent solid, and thus has the potential for use in solid state electrochromic devices. The plasticizer is added to the polymer electrolyte to increase the ionic conductivity, which is a concern with respect to the switching speeds of electrochromic devices [1,21. Methacrylate-based polymers containing ethyleneoxide units, either as sidechains or incorporated in crosslinks, have been explored previously as hosts for solid polymer electrolytes, with and without plasticisers [3-71. A monoacrylate-based polymer was chosen for this work because of the more flexible backbone of the polyacrylates. The use of plasticizers to increase the conductivity of solid polymer electrolytes to the order of 10m3 S cm-’ is well known [4,8-141. Plasticizers have also been used to increase the ionic conductivity of polyelectrolytes [ 151. Plasticizers with high dielectric constants, such as propylene carbonate or ethylene carbonate, increase both the number of charge carriers and ion mobility in the polymer electrolyte by solvating the complexed salt. Similar results are seen by adding cryptand ligands to Na+-conducting polyelectrolytes 1161. Another example of the effect of a strong propylene carbonate plasticizer-salt interaction is presented for the polymer electrolyte described here.