G. Vaivars

Electrochromic devices embodying W oxide/Ni oxide tandem films

Six-layer electrochromic devices of indium tin oxide (ITO)/NiOxHy/WO3/ZrP-electrolyte/WO3/ITO were made by reactive dc magnetron sputtering and lamination. The WO3 layer between the acidic ZrP-based electrolyte and the NiOxHy layer served as optically passive protective layer. The optical inactivity of the protective layer could be understood from arguments based on electron density of states.

Proton conducting composite electrolytes based on antimonic acid

Abstract This report concerns a composite proton electrolyte suitable for use in electrochromic devices. The electrolyte consists of nanosize pyrochlore antimonic acid particles suspended in a poly(vinyl acetate) matrix by a gel route. It was found possible to substitute the antimonic acid by inert oxides of aluminum and silicon, thus making the electrolyte less harmful to the oxide electrodes of the electrochromic devices without considerably decreasing the conductivity. The proton conductivity of the antimonic acid electrolyte was ∼10 −4 S/cm at room temperature, practically independent of its amount of absorbed water.

Antimonic acid hydrate xerogels as proton electrolytes

Abstract Two high stability types of protonic solid electrolytes based on antimonic acid hydrate xerogels have been obtained by the sol-gel technique: Sb 2 O 5 ·(3–4)H 2 O (colloidal) and Sb 2 O 5 ·5H 2 O (polymeric). The first one is a white compact material with conductivity 0.40 mS/cm (298 K) for n =3.7. The last one is transparent for visible light with a conductivity of 0.80 mS/cm. An electrochromic system based on the colloidal gel electrolyte in the form of paste has good performance-more than 10 7 cycles and a lifetime of more than five years.

Proton conducting polymer composites for electrochromic devices

Abstract This report describes composite proton electrolytes composed of nanosize zirconium phosphate or antimonic acid particles suspended in a poly(vinyl acetate)/glycerin gel matrix. The proton conductivity was 10 −3 –10 −4 S/cm at room temperature, thermal stability prevailed up to at least 110°C, and compatibility was found with oxide electrodes; these properties makes the electrolyte suitable for use in solid state electrochemical devices. The temperature dependence of the conductivity was found to obey the Williams-Landel-Ferry relationship at temperatures over 60°C, thus suggesting that the ion conductivity in the composite electrolyte can be described by mechanisms normally taken to be valid for liquid ion conductors.

Sol-gel produced humidity sensor

Abstract The sol-gel produced polycrystalline Prussian Blue thick films as planar humidity sensors have been investigated by impedance spectroscopy. The equivalent circuit used allows simulation in all the investigated r.h. range (10–100%). The region of changes of sample resistance is about five orders, which is enough for high measuring sensitivity.

Cerium-containing counter electrodes for transparent electrochromic devices

Films of Me-Ce oxide (Me: Ti, Zr, Sn, W) and of Ni-Ce hydroxide were produced by reactive magnetron co-sputtering. Li intercalation in Me-Ce oxide, and H exchange in Ni-Ce hydroxide, were accomplished electrochemically. Electrochromism was quenched in proportion with the Ce content in Me-Ce oxide. Films of Zr-Ce (and to some extent Ti-Ce) oxide were able to serve as fully transparent counter electrodes, of much interest for transparent electrochromic devices. In Ni-Ce hydroxide, the Ce addition enhanced the capacity for charge exchange.

Synthesis, structure and conductivity of Ag2ZnSiO4, Ag2ZnGeO4 and Ag2BeSiO4

Abstract The compounds Ag 2 MM′O 4 with MM ′ = ZnSi , ZnGe and BeSi have been synthesised by reacting the corresponding Na compounds with molten AgNO 3 . The crystal structures of Ag 2 ZnSiO 4 and Ag 2 ZnGeO 4 have been refined from Cu K α 1 powder diffractometer data by the Rietveld technique to R F = 3.3 and 7.1%, respectively. They are isostructural with monoclinic Na 2 ZnSiO 4 . The powder pattern of Ag 2 BeSiO 4 indicates that it is isostructural with orthorhombic Na 2 BeSiO 4 . The conductivity of the compounds has been determined using ac impedance measurements. Ag 2 ZnSiO 4 and Ag 2 BeSiO 4 are ionic conductors, with conductivities that are very similar to those of their corresponding isostructural Na compounds. Ag 2 ZnGeO 4 is an electronic semiconductor with σ(60 ° C ) = 1.0 × 10 −2 (Ω cm ) −1 .

Gas-sensitive gap formation by laser ablation in In2O3 layer: application as humidity sensor

Abstract A new method of preparing a gas-sensitive device by laser ablation of a thin gap in a thin conducting In2O3 layer has been discovered. In the bottom of the gap no products from In2O3 are found, thereby indicating that the reorganized surface of the glass substrate is responsible for the humidity sensitivity. Impedance spectra of the gap processed by a laser beam are measured in the humidity range RH25–100% at temperatures T0–45°C, where a linear dependence of the logarithm of resistivity on the values of humidity is estimated.

ELECTROCHROMIC DEVICES INCORPORATING Cr OXIDE AND Ni OXIDE FILMS: A COMPARISON

Abstract Transparent films of Cr oxide and Ni oxide were made by reactive DC magnetron sputtering in Ar+O2+H2. They displayed anodic electrochromism with charge capacities similar to that of W oxide. Cr oxide was stable in acidic environments, while Ni oxide was stable in basic environments. Electrochromic devices were made with pristine Cr oxide or Ni oxide films operating in conjunction with W oxide and a proton conducting electrolyte. Of the two oxides, Cr oxide film allowed device operation at a lower voltage span, while the device with Ni oxide film yielded a higher transmittance in the bleached state, a larger absorptance modulation, and a more neutral color.

Gaseous sensors based on solid proton conductors

Abstract he chemical sensors for different gaseous (alcohol, acetone, ammonia, water vapour) detection at room temperature are developed by using polycrystalline β-alumina and xerogel of antimonic acid hydrate (AAH). The sensitivity and selectivity of sensors depend on the ion-exchange and preparative methods. The possibility of producing different types of potentiometric, amperometric, voltammetric and resistance sensors on the basis of these ion-conducting materials is shown. More success is achieved by producing ammonia-sensitive devices on β-alumina as well as on AAH xerogel.