Abstract: Combustible gas detecting element for detecting the existence of combustible gas such as methane, ethane, propane iso-butane and hydrogen. The element comprises .alpha.-Fe.sub.2 O.sub.3 containing a small amount of sulfate ion (SO.sub.4.sup.--). By using a precipitation process with urea as a precipitant for preparing the above .alpha.-Fe.sub.2 O.sub.3, remarkably high stability and reliability can be released. Addition of quadrivalent metal of Sn, Zr or Ti to the .alpha.-Fe.sub.2 O.sub.3 greatly enhances the gas sensitivity to those gases. Furthermore the sensitivity to carbon monoxide was also enhanced by adding cadmium (Cd) and/or gold (Au).

Abstract: A combustible gas detecting element, the sensitive element of which has at least one material selected from the group consisting of gamma-type ferric oxide (.gamma.-Fe.sub.2 O.sub.3) and alpha-type ferric oxide (.alpha.-Fe.sub.2 O.sub.3) and has a microstructure with an average grain size smaller than 0.5 micrometers and a porosity of from 35 to 85%. The sensitivity is increased by adding at least one material selected from a group consisting of tin (Sn) and zinc (Zn) in a ratio from 0.5 to 70 mol %, based on stannic oxide (SnO) and zinc oxide (ZnO) relative to the ferric oxide component. The element is manufactured from fine particles obtained by coprecipitating metallic ions from a solution containing Fe ions and at least one member selected from the group consisting of Sn ions and Zn ions, and the fine particles are pressed and then sintered or are formed into a paste, printed on a substrate and then sintered.

Abstract: There is provided a novel combustible gas detecting element and method for production thereof. The element comprises a gas sensing body comprising a sintered body or film of an amorphous semiconductor comprising a metal oxide, a sulfate and halide.

Abstract: Combustible gas detecting element for detecting the concentration of a combustible gas such as isobutane, ethane, propane and hydrogen. It comprises .gamma.-Fe.sub.2 O.sub.3, .gamma.-Al.sub.2 O.sub.3 and at least one of La, Ce, Pr and Nd in terms of La.sub.2 O.sub.3, Ce.sub.2 O.sub.3, Pr.sub.2 O.sub.3 and Nd.sub.2 O.sub.3, respectively. This gas detecting element is an improvement over .gamma.-Fe.sub.2 O.sub.3, and is advantageous for its highly stable load life even under severe conditions of a high temperature and a high humidity and for its high sensitivity to a combustible gas.