Abstract: A ceramic heater in which a damage in a joining portion between a heating portion and a lead portion is suppressed and the reliability is excellent is provided. In a ceramic heater (1) including: a rod-shaped support (2) which is made from an insulative ceramic; and a resistor member (3) including a heating portion (31) embedded in a tip end part of the support (2), and a pair of lead portions (33) which extend from the heating portion (31) toward a rear end side of the support (2), the heating portion (31) and the lead portions (33) are made from the same conductive ceramic.

Abstract: The present invention relates to a ceramic heater which is capable of preventing an electric conduction defect of a heat-generating resistor from being caused by a supplied current, thus being excellent in voltage endurance, and a glow plug containing the ceramic heater. The ceramic heater 2 contained in the glow plug 1 has an insulative ceramic base material 21 and the heat-generating resistor 22 embedded in the insulative ceramic base material. The heat-generating resistor 22 has, as main components, an electrically conductive compound, silicon nitride and a grain boundary amorphous glass phase. The amount of the rare earth element contained in the heat-generating resistor is less than 2% by volume in terms of its oxide and, further, a molar ratio R=(A/A+B) of the mol number A of the amount of the rare earth element in terms of its oxide to a total of the mol number A and a mol number B, which is the amount of excess oxygen in terms of silicon dioxide, is 0.3 or less.

Abstract: A ceramic heater in which a damage in a joining portion between a heating portion and a lead portion is suppressed and the reliability is excellent is provided. In a ceramic heater (1) including: a rod-shaped support (2) which is made from an insulative ceramic; and a resistor member (3) including a heating portion (31) embedded in a tip end part of the support (2), and a pair of lead portions (33) which extend from the heating portion (31) toward a rear end side of the support (2), the heating portion (31) and the lead portions (33) are made from the same conductive ceramic.

Abstract: The present invention relates to a ceramic heater which is capable of preventing an electric conduction defect of a heat-generating resistor from being caused by a supplied current, thus being excellent in voltage endurance, and a glow plug containing the ceramic heater. The ceramic heater 2 contained in the glow plug 1 has an insulative ceramic base material 21 and the heat-generating resistor 22 embedded in the insulative ceramic base material. The heat-generating resistor 22 has, as main components, an electrically conductive compound, silicon nitride and a grain boundary amorphous glass phase. The amount of the rare earth element contained in the heat-generating resistor is less than 2% by volume in terms of its oxide and, further, a molar ratio R=(A/A+B) of the mol number A of the amount of the rare earth element in terms of its oxide to a total of the mol number A and a mol number B, which is the amount of excess oxygen in terms of silicon dioxide, is 0.3 or less.

Abstract: A silicon nitride sintered material containing a silicon nitride component and silicon carbide having an average particle size of 1 ?m or less in an amount of at least 1 mass % and less than 4 mass %, based on 100 mass % of the silicon nitride component. The carbide is dispersed in the silicon nitride component, and the silicon nitride sintered material has a thermal expansion coefficient of at least 3.7 ppm/° C. between room temperature and 1,000° C. The silicon nitride component contains a rare earth element in an amount of 15-25 mass % as reduced to a certain oxide thereof and Cr in an amount of 5-10 mass % as reduced to a certain oxide thereof, and a crystalline phase is present in intergrain regions of the sintered material.

Abstract: A silicon nitride sintered material containing silicon nitride, a Group 4a through 6a element, a rare earth element, and silicon carbide, characterized in that the amount of the rare earth element as reduced to a certain oxide thereof is 5.7-10.3 mol %; the ratio by mol of subtraction remainder oxygen amount calculated in relation to the oxygen contained in the sintered material, the remainder oxygen amount being expressed in terms of silicon dioxide, to the amount of oxygen contained in the sintered material is at least 0.50 and less than 0.70; a four-component crystalline phase of rare earth element-silicon-oxygen-nitrogen is not present; and the thermal expansion coefficient is at least 3.7 ppm/° C. between room temperature and 1,000° C.

Abstract: A silicon nitride—tungsten carbide composite sintered and process for preparing the same which contains silicon nitride and tungsten carbide, and is characterized in that the total in amounts of an entirety of rare earth elements as reduced to certain corresponding oxides thereof, the elements being contained in the sintered material, and excess oxygen as reduced to silicon dioxide is 6-20 mass %; the ratio, on a mol basis, of (the amounts of rare earth elements as reduced to the certain corresponding oxides thereof)/(the amounts of the rare earth elements as reduced to the corresponding oxides thereof+the amount of excess oxygen as reduced to silicon dioxide) is 0.3-0.7; a crystalline phase is present in an intergrain region of the sintered material; and an effective firing temperature range within which a flexural strength of at least 800 MPa is obtained encompasses at least 100 degrees.

Abstract: A silicon nitride-tungsten carbide composite sintered material which contains silicon nitride and tungsten carbide, and characterized in that in an arbitrary cross-section of the sintered material, the ratio of the area of a tungsten carbide portion to that of the entirety of the cross-section is 20-35%, and a tungsten carbide aggregation portion having a longitudinal length of at least 5 &mgr;m is present in the arbitrary cross-section. The production process includes firing raw material powder containing tungsten carbide powder and two silicon nitride powders having different particle sizes.

Abstract: An insulator for spark plug comprises an alumina-based sintered body comprising: Al2O3 as a main component; and at least one component (hereinafter referred to as “&bgr; component”) selected from the group consisting of Ca component, Sr component and Ba component, wherein the alumina-based sintered body comprises particles comprising a compound comprising the &bgr; component and Al component, the compound having a molar ratio of the Al component to the &bgr; component of 4.5 to 6.7 as calculated in terms of oxides thereof, and has a relative density of 90% or more.

Abstract: A silicon nitride sintered material containing silicon nitride, a Group 4a through 6a element, a rare earth element, and silicon carbide, characterized in that the amount of the rare earth element as reduced to a certain oxide thereof is 5.7-10.3 mol %; the ratio by mol of subtraction remainder oxygen amount calculated in relation to the oxygen contained in the sintered material, the remainder oxygen amount being expressed in terms of silicon dioxide, to the amount of oxygen contained in the sintered material is at least 0.50 and less than 0.70; a four-component crystalline phase of rare earth element-silicon-oxygen-nitrogen is not present; and the thermal expansion coefficient is at least 3.7 ppm/° C. between room temperature and 1,000° C.

Abstract: A silicon nitride-tungsten carbide composite sintered material which contains silicon nitride and tungsten carbide, and characterized in that in an arbitrary cross-section of the sintered material, the ratio of the area of a tungsten carbide portion to that of the entirety of the cross-section is 20-35%, and a tungsten carbide aggregation portion having a longitudinal length of at least 5 &mgr;m is present in the arbitrary cross-section. The production process includes firing raw material powder containing tungsten carbide powder and two silicon nitride powders having different particle sizes.

Abstract: A silicon nitride sintered material containing a silicon nitride component and silicon carbide having an average particle size of 1 &mgr;m or less in an amount of at least 1 mass % and less than 4 mass %, based on 100 mass % of the silicon nitride component. The carbide is dispersed in the silicon nitride component, and the silicon nitride sintered material has a thermal expansion coefficient of at least 3.7 ppm/° C. between room temperature and 1,000° C. The silicon nitride component contains a rare earth element in an amount of 15-25 mass % as reduced to a certain oxide thereof and Cr in an amount of 5-10 mass % as reduced to a certain oxide thereof, and a crystalline phase is present in intergrain regions of the sintered material.

Abstract: A silicon nitride—tungsten carbide composite sintered and process for preparing the same which contains silicon nitride and tungsten carbide, and is characterized in that the total in amounts of an entirety of rare earth elements as reduced to certain corresponding oxides thereof, the elements being contained in the sintered material, and excess oxygen as reduced to silicon dioxide is 6-20 mass %; the ratio, on a mol basis, of (the amounts of rare earth elements as reduced to the certain corresponding oxides thereof)/(the amounts of the rare earth elements as reduced to the corresponding oxides thereof+the amount of excess oxygen as reduced to silicon dioxide) is 0.3-0.7; a crystalline phase is present in an intergrain region of the sintered material; and an effective firing temperature range within which a flexural strength of at least 800 MPa is obtained encompasses at least 100 degrees.

Abstract: An insulator for spark plug comprises an alumina-based sintered body comprising: Al2O3 (alumina) as a main component; and at least one component (hereinafter referred to as “E. component”) selected from the group consisting of Ca (calcium) component, Sr (strontium) component and Ba (barium) component, wherein the alumina-based sintered body comprises particles comprising a compound comprising the E. component and Al (aluminum) component, the compound having a molar ratio of the Al component to the E. component of 4.5 to 6.7 as calculated in terms of oxides thereof, and has a relative density of 90% or more.

Abstract: Disclosed is an alumina-based sintered material comprising a magnesium component, a calcium component, a silicon component, and a lithium component, wherein the content of the lithium component in terms of oxide amount is from 0.002 to 0.04% by weight based on the alumina-based sintered material.