OXYGEN SENSOR

PURPOSE:To detect the change in concentration of oxygen by making use of the fact that the resistance ratio is changed when oxygen enters or goes out from a van der Waals gap of a low-dimensional substance. CONSTITUTION:A monocrystal of a conductive substance in the first- or second- dimensional crystal structure, for example, CuFeTe2 is formed and crushed to be powdered crystallites. Thereafter, the crystallites are pressurize uniaxially to have orientation, thereby to form a plate-like pellet P. Silver electrodes 1, 2 are provided all over the upper and lower surfaces of the pellet P, whereby a sensor element to measure the resistance ratio rho1 in a direction of lamination is obtained. Moreover, a plurality of belt-shaped silver electrodes 5, 6 are provided with the same distance on the upper surface of the pellet P, whereby a sensor element to measure the resis tance ratio rho11 in a direction of layer is obtained. These sensor elements are fixed to sample holder 10 within a 'Pyrex (R)' tube 9. The tube 9 is connected to a rotary pump 12 and an oxygen gas holder 13. An oxygen gas is introduced into the tube 9 and discharged thereform at each constant time. Although the resistance ratio rho11 is not changed at this time, the resistance ratio rho1 is changed considerably consequently to the introduction and discharge of the oxygen. Therefore, the change in concentration of oxygen in the environs can be detected.