Abstract: Process for the preparation of a ceramic wherein: 50% to 75% by weight of a compound intended to form a conductive phase, and 25 % to 50% by weight of one or more materials allowing the formation of insulating phases composed of silicon nitride and modified silicon oxynitride are mixed in a receptacle containing a liquid after a thermal treatment leading to sintering of the ceramic; this mixture is subjected to grinding, drying and sieving operations; this mixture is pressed; and this mixture is sintered so as to obtain a ceramic with a porosity of between 0 and 30%. The sintering is carried out under a pressure of at least 50 bar of a gas which is inert towards the constituents of the mixture. Ceramic thus obtained and spark plug comprising it.

Abstract: Method for manufacturing a high-energy, low-voltage ignition plug comprising a ceramic material between its electrodes: there is mixed, in a container containing a liquid, from 50 to 75% of a compound which is intended to form a conductive phase and from 25 to 50% of one or more materials which allow the formation of phases of yttrium garnet after thermal processing; operations are carried out for pulverising, drying and sieving the admixture; the admixture is pressed or injected into a mould; sintering is carried out so as to obtain a ceramic material having porosity of between 0 and 30%; the ceramic material is used in order to constitute the material located between the electrodes of a high-energy, low-voltage ignition plug. Ignition plug manufactured in that manner.

Abstract: Method for preparing a semi-conductive ceramic material, wherein: in a receptacle containing a liquid, there are mixed from 30 to 90% of a conductive phase based on Z1-xMxCrO3 for 0?X?0.3, with Z being an element of the lanthanide group or a mixture of elements of this type, and M being calcium, strontium, magnesium, aluminum, titanium, yttrium or a mixture of two or more of these elements; from 8 to 60% of an insulating phase based on fine grains of alumina or tabular alumina or mullite or a mixture of two or more of these compounds; and from 0 to 10% of sintering additives; operations are carried out for milling, drying and sieving this mixture; this mixture is pressed; and this mixture is sintered in order to obtain a ceramic material having a porosity less than or equal to 25%.