V. Leonhard

Thin and thick film electrochemical CO2 sensors

Abstract Thin and thick film electrochemical CO 2 -sensors were constructed by incorporating a sodium ion conductor like NASICON or β-alumina with a solid, gas sensitive layer such as Na 2 CO 3 as measuring electrode. Our results confirmed, in accordance with works published by Maruyama et al. that the EMF of the cell depends logarithmically on the CO 2 partial pressure in a CO 2 /O 2 gas mixture. For the practical use, however, stability, sensitivity and selectivity of the sensors should still be improved.

Thick-film chemical sensors

Abstract Chemical gas sensors with solid electrolytes have been prepared by the thick-film screen-printing technique. Nasicon or zirconia (YSZ) solid ion conductors are used, which have been deposited on α-alumina substrates. An all-thick-film potentiometric H 2 sensor based on Nasicon containing a Na x WO 3 reference electrode and a porous Pt working electrode and an all-thick-film potentiometric O 2 sensor based on zirconia with a Pd/PdO reference electrode and a porous Pt working electrode have been produced. Development of a CO 2 sensor based on Nasicon or β-alumina with an Na 2 CO 3 working electrode is the object of the current research work. Also a thick-film oxygen sensor based on the limiting current behaviour of a zirconia pumping cell has been investigated.

NASICON electrode for detecting sodium ions

Abstract Solid electrolytes are used for electrochemical devices like batteries, fuel cells and sensors. NASICON, a ceramic Na + conductor, has been used as a sensitive membrane for an Na + -sensitive electrode for several years. In this contribution we report on the stability of NASICON in aqueous solutions and on the characteristic of an Na + -sensitive electrode with NASICON as membrane. Such a membrane can be prepared by conventional ceramic techniques but also by the screen printing technique. An all thick film electrode with NASICON as sensitive membrane and sodium tungsten bronze as internal reference electrode is less sensitive to Na + than an electrode with a membrane in pellet form.

Investigations on counter electrode materials for solid state electrochromic systems

Abstract Investigations have been carried out on mixed oxide systems (WO3)x(Li2O)y(MO)z, with M = Fe, Mn, V, Ce, Sb or Nb and 0.3 and 0.26 . Cyclic voltammetric measurements in a 1 N LiClO4- propylene carbonate electrolyte with an AgAgCl-reference electrode were used to study the insertion of Li+ ions into, and the extraction of the inserted ions from, the proposed compounds. However, the main problem is still the insufficient transparency of these materials. Problems concerning preparation of the thin film oxides are also noted.

Solid State Chemical Sensors in Thick Film Technique

Chemical sensors with solid ion-conductors have been prepared by thick film screen printing method. Solid ion conductors Nasicon (Na1+xZr2SixP3−xO12) and YSZ (yttria stabilized zirconia) have been deposited onto α-alumina substrate. An all-thick film hydrogen sensor based on Nasicon electrolyte with sodium tungsten bronze (NaxWO3) reference electrode and porous platinum working electrode and an oxygen sensor based on zirconia electrolyte with Pd/PdO-reference electrode have been developed. Development of carbon dioxide sensor based on Nasicon or β-alumina with sodium carbonate working electrode will be the objective of the current research work.