Abstract: An element for detection of NO.sub.x gas in which at least one titanium-containing oxide which is selected from the group of(a) titanium oxide,(b) a solid solution wherein at least one element from the group of aluminum (Al), gallium (Ga), indium (In), scandium (Sc), magnesium (Mg), yttrium (Y), neodymium (Nd), tantalum (Ta), antimony (Sb) and arsenic (As) is contained in the solid-solution state in the titanium oxide, and(c) an oxide which contains titanium and other metal element(s) and has a perovskite structure,and has such an oxygen deficiency that its nonstoichiometric parameter (.delta.) is in the range of 0.03 to 0.3. Thereby, NO.sub.x of an exhaust gas can be measured easily.

Abstract: A thermistor element composed substantially of a vanadium-containing titania having dissolved therein 0.01 to 10 at. %, based on titanium, of vanadium and optionally 10 at. % or less, based on titanium, of at least one element selected from the group containing of cobalt, copper, manganese, iron, nickel, bismuth, strontium, barium, lead and zinc. A gas sensor using the thermistor element as a temperature sensor is described.

Abstract: A method of producing an exhaust gas sensor incorporating BaSnO.sub.3. Stannate ion and barium ion are reacted in a strong alkali to precipitate water-containing crystals of BaSnO.sub.3 such as BaSnO.sub.3.3H.sub.2 O, BaSnO.sub.3.5H.sub.2 O or the like. When thermally decomposed, the precipitate gives BaSnO.sub.3 free from segregated Ba and Sn elements. The product was then molded and thereafter sintered to obtain the sensor.