Abstract: A process for producing a ceramic having a microstructured surface with a surface profile depth of less than 1 micron, measured by the atomic force microscopy, comprising preparing a polymeric precursor material, shaping the precursor material into a structured mold insert of an inherently stable mold insert material having a structured surface geometry corresponding with the microstructured surface of the ceramic to form a shaped precursor material, the shaped precursor material being rendered infusible by chemical crosslinking, and wherein the inherently stable mold insert material is selected from materials having sufficient strength for structuring and high molding accuracy, and pyrolyzing the shaped precursor material, whereby the ceramic having the microstructured surface is obtained.

Abstract: In the process for producing a homogeneous and finely crystalline silicon nitride ceramic, ceramic powder is milled, mixed with shaping aids, the mixture is shaped into parts and the shaped parts are subsequently sintered in a nitrogen atmosphere. According to the invention, sintering is carried out in a multistage process at temperatures T.sub.max in the range from 1700.degree. to 1900.degree. C. using gas pressures in the range from 0.3 to 50 MPa. In a first temperature stage, a temperature from 0.9 to 0.96.multidot.T.sub.max is maintained over a time period from 10 to 50 minutes at an N.sub.2 pressure from 0.2 to 1.2 MPa, while in a second temperature stage a temperature from 0.97 to 0.985.multidot.T.sub.max is maintained over a time period from 20 to 80 minutes at an N.sub.2 pressure from 3 to 6 MPa. Then the temperature is increased to T.sub.max and the pressure is increased to from 7 to 50 MPa.

Abstract: A planar sensor made of ceramic material, for measuring and detecting combustible gases and/or the oxygen content in furnaces or in the exhaust gases of internal combustion engines, is described. The sensor has an at least five-layered structure on the basis of a combination of three zirconium dioxide layers with two aluminum oxide layers, a metallic heating resistor being embedded between two aluminum oxide layers, and three zirconium dioxide layers being combined with two platinum electrodes and one further electrode made of a binary or ternary alloy of platinum with gold, nickel, copper, rhodium, ruthenium, palladium or titanium. A process for fabricating the sensor is also described. It is also possible for the sensor to be combined, according to the invention, with a suitable housing which on its outside is provided with connecting wires and plugs for transmitting the measured signals.