Showing papers by "Claes-Göran Granqvist published in 1995"

Handbook of inorganic electrochromic materials

Abstract: Part 1 Case study on tungsten oxide: bulk crystalline tungsten oxide tungsten oxide films - preparation, structure, and composition of evaporated films tungsten oxide films - preparation, structure, and composition of sputter-deposited films tungsten oxide films - preparation, structure, and composition of electrochemically and chemically prepared films tungsten oxide films - ion intercalation/deintercalation studied by electrochemical techniques tungsten oxide films - ion intercalation/deintercalation studied by physical techniques tungsten oxide films -ultraviolet absorption and semiconductor bandgap tungsten oxide films - optical properties in the luminous and near-infrared range tungsten oxide films - theoretical models for the optical properties tungsten oxide films - electrical properties. Part 2 Electrochromism among the oxides (except tungsten oxide): molybdenum oxide films miscellaneous tungsten- and molybdenum-oxide-containing films iridium oxide films titanium oxide films manganese oxide films vanadium dioxide films vanadium pentoxide films nickel oxide films cobalt oxide films niobium oxide films miscellaneous oxide films systematics for the electrochromism in transition metal oxides inorganic non-oxide electrochromic materials. Part 3 Electrochromic devices: transparent electrical conductors electrolytes and ion conductors ion storage materials - brief overview devices with liquid electrolytes devices with solid inorganic electrolytes and ion conductors devices with polymer electrolytes time-dependent device performance - a unified treatment.

Determination of fractal dimension by cyclic i-v studies: the laplace-transform method

Abstract: A method is introduced for the determination of fractal dimension ${\mathit{d}}_{\mathit{f}}$ from cyclic voltammograms taken on films in contact with an electrolyte. It is based on a Laplace transform of the Nernst equations using Riemann-Liouville transform expressions for the surface concentrations. Diffusion-limited conditions are required. The method is applicable even when resistance drops are present in the electrolyte or across the film. Our Laplace transform method gave correct results for gold electrodes with known ${\mathit{d}}_{\mathit{f}}$ and it also provided a fractal dimension of a partially active In oxide surface in good agreement with that obtained from an independent technique.

Physical and electrochemical properties of Li-intercalated Sn oxide films made by sputtering

Abstract: Sn oxide films were made by reactive rf magnetron sputtering under conditions that led to both electronic and ionic conductivity. The film structure was studied by X-ray diffraction and Atomic Force Microscopy (AFM). Li+ intercalation produced electrochromism with coloration efficiency peaked in the infrared. Cyclic voltammograms taken at different sweep rates were interpreted in terms of a unique structural parameter related to the fractal dimension of a self-affine surface relief and in excellent agreement with the fractal dimension as obtained with AFM. Mossbauer spectroscopy was used to determine the valence state of the Sn-atoms; a change from Sn4+ to Sn2+ was detected after electrochemical intercalation of Li+.

Tungsten Oxide Films: Preparation, Structure, and Composition of Evaporated Films

Abstract: Electrochromism has been investigated in considerable detail in evaporated W oxide films. This chapter provides an introduction on deposition aspects followed by a detailed account on density as a function of evaporation parameters. It provides a discussion of elemental composition and of microstructure apparent from electron microscopy and X-ray extinction. It focuses on vibrational properties with regard to Raman spectroscopy and infrared absorption spectroscopy. It uses this information to formulate models for the structure at different levels: local cluster-type models and descriptions of larger columnar features. It concludes with the crystallization of as-deposited films. Crystallization can be induced not only by annealing at a high temperature but also by treating evaporated films at a moderately elevated temperature at a high relative humidity. From a combination of electron diffraction and XRD measurements, it was inferred that the crystallization starts at the air interface and progresses so that it extends across a ∼ 1 μm thick layer after ∼1 day. It was argued that the crystallization was connected with the dissociation of W-O-W bonds and the formation of WO 3 · H 2 0 or H 2 WO 4 · H 2 O with a dense glassy structure. It is possible that these processes are akin to those in the common “sealing” of anodic alumina.

Vanadium Dioxide Films

Abstract: Vanadium dioxide has attracted a lot of interest because of its unique capability of going from a semiconducting monoclinic phase to a (semi)metallic tetragonal rutile phase at a temperature in the vicinity of room temperature, specifically at 68°C. This chapter discusses the atomic displacements in the structural transformation, which motivates that the V-dioxide-based films together with the other rutile-type electrochromic oxides. It focuses on crystal structures and electrical properties of bulk-like V dioxide, preparation and characterization of thin films, ion intercalation/deintercalation reactions and ensuing changes in electrical conductivity, and optical properties. Vanadium dioxide films have been prepared by many techniques. Some of the films were prepared by ion-assisted deposition or were converted into a dioxide by annealing post-treatment. One should observe in this context that when solid VO 2 is heated, the liberated species are predominantly VO 2 molecules. CVD with V oxychloride, V acetylacetonate, or V triisobutoxide, and thermal decomposition of V naphthenate, are other useful techniques. Also, simple thermal oxidation of metallic vanadium is a viable technique for making V dioxide films.

DC Magnetron Sputtered Mo-Ti Oxide Films for Color Neutral Electrochromic Devices

Abstract: Mo-Ti oxide films with compositions ranging from MoO3 to TiO2 were prepared by reactive DC magnetron sputtering using a newly developed high-rate technique with interacting plasma zones. Optical and electrochemical measurements showed that an increase of the Ti content yielded increased electrochemical stability, decreased coloration efficiency, and increased potential for electrochromic coloration. The films have interesting properties for color-neutral electrochromic devices.