Abstract: An oxygen sensor element having an oxygen ion-permeable solid electrolyte having a tabular or columnar shape and electrode layers formed on the solid electrolyte. At least one of the electrode layers is composed of a fired body having a uniform structure consisting of 100 weight parts of a metal and 0.1 to 10 weight parts of a glass which consists of the following materials in molar amounts: SiO.sub.2, 62-75%; ZrO.sub.2, 7-11%; R.sub.2 O, 13-23%; R'O, 1-10%; Al.sub.2 O.sub.3, 0-4%; B.sub.2 O.sub.3, 0-6%; Fe.sub.2 O.sub.3, 0-5%; CaF.sub.2, 0-2%; and TiO.sub.2, 0-4%; wherein R.sub.2 O is Na.sub.2 O which is substantially pure or is substituted by Li.sub.2 O within 2 mole percent thereof, and R'O is an oxide selected from the group consisting of the alkaline-earth metal oxides, ZnO and MnO. Disclosed also is a method of producing the oxygen sensor element.

Abstract: A leanness sensor has a sensor element made of an oxygen-permeable solid electrolyte and having a cylindrical form or a form like a vessel closed at one end thereof. The sensor element is provided with metallic electrodes formed on the inner and outer surfaces thereof. An inner metallic member and an outer metallic member are mounted on the sensor element and electrically connected to the metallic electrodes. The sensor element is fixed to the inner side of the end portion of a cylindrical insulating tube.

Abstract: A lean sensor for sensing oxygen concentration in exhaust emissions, including a sensor element consisting of a tabular solid electrolyte having opposed sides provided with electrodes with at least one surface thereof coated with a porous coating layer, an element fixing plate having an element fitting hole to which the element is fitted, and a pair of heat-resistant insulating support plates having opposing windows and clamping therebetween the element fixing plate together with the sensor element disposed in the windows. In this way, it is possible precisely to locate the element in relation to the plate and to improve the bonding strength and reliability while reducing the size of the sensor as a whole.