Abstract
The conductivity of a solid-state electrochemical cell with LaF3 vapor deposited film as electrolyte varies with the concentration of oxygen in the ambient atmosphere at room temperature. Some fundamental experiments have been carried out in order to realize a solid-state oxygen sensor with LaF3 vapor deposited film. The merits of the sensor are that it can be used at room temperature withouth eating, not like a ZrO2 oxygen sensor, and that it can be easily made small because it makes use of a solid-state cell.
Oxygen sensors with Au as a cathode, La or Cu as an anode, and LaF3 vapor deposited film or single crystal as a solid electrolyte have been fabricated, and their characteristics such as the current sensitivity to the oxygen concentration and the current responce to the change of oxygen concentration have been measured. It has been observed that the cell current is proportional to the logarithm of the oxygen concentration and the responce time is about 3 minutes for the vapore deposited film cells and about 20 minutes for the single crystal cell.
The structure of LaF3 vapor deposited film has been studied by means of reflection high energy electron diffraction. The LaF3 vapor deposited film has a polycrystalline structure and its grain orientation depends on the deposition conditions.
The material transport through the film has been studied by means of Auger electron spectroscopy in conjunction with Argon ion sputtering. Some oxygen deposition have been observed at the anode interface of the sensor, after a few days operation.
These experimental results indicate that the LaF3 oxygen sensor responds to oxygen by the following sequence: reduction of oxygen at the cathode, oxygen ion transport through the LaF3 film, and oxidation of the anode metal.
