[Object] To provide a gas nozzle which meets a requirement to suppress the fall of particles. [Solution] A gas nozzle 4 according to an aspect of the present invention includes a columnar main body 13 formed of a ceramic sintered body provided with a through-hole 12 formed therein through which a gas flows, an exhaust port 15 of the through-hole 12 for the gas is formed in one end surface S1 of the main body 13, and the mean width of the profile elements (Rsm) of the one end surface S1 is 5 times or more the average crystalline grain diameter of the ceramic sintered body.

A composite material consisting of aluminium oxide as a ceramic matrix and zirconium oxide dispersed therein. A method for the production thereof, components containing the composite and methods of using the same are also provided.

A silicon nitride substrate including silicon nitride crystal grains and a grain boundary phase and having a thermal conductivity of 50 W/m.Math.K or more, wherein, in a sectional structure of the silicon nitride substrate, a ratio (T2/T1) of a total length T2 of the grain boundary phase in a thickness direction with respect to a thickness T1 of the silicon nitride substrate is 0.01 to 0.30, and a variation from a dielectric strength mean value when measured by a four-terminal method in which electrodes are brought into contact with a front and a rear surfaces of the substrate is 20% or less. The dielectric strength mean value of the silicon nitride substrate can be 15 kV/mm or more. According to above structure, there can be obtained a silicon nitride substrate and a silicon nitride circuit board using the substrate in which variation in the dielectric strength is decreased.

A method for manufacturing an alumina sintered body, according to the present invention, includes the steps of (a) obtaining a compact by putting a slurry containing an Al.sub.2O.sub.3 powder, a MgO powder, a MgF.sub.2 powder, a solvent, a dispersing agent, and a gelatinizer into a mold, gelatinizing the slurry by a chemical reaction of the gelatinizer in the mold, and causing mold release, (b) obtaining a calcined body by drying the compact, performing degreasing, and further performing calcination, and (c) obtaining a ceramic sintered body by subjecting the calcined body to hot-press firing at 1,150 C. to 1,350 C. In the step (a), the Al.sub.2O.sub.3 powder having a purity of 99.9 percent by mass or more is used and 0.1 to 0.2 parts by mass of MgO powder and 0.13 parts by mass or less of MgF.sub.2 powder relative to 100 parts by mass of Al.sub.2O.sub.3 powder are used.

A barium titanate piezoelectric ceramic having good piezoelectric properties and mechanical strength and a piezoelectric element that includes the ceramic are provided. A method for making a piezoelectric ceramic includes forming a compact composed of an oxide powder containing barium titanate particles, sintering the compact, and decreasing the temperature of the compact after the sintering. The sintering includes (A) increasing the temperature of the compact to a first temperature within a temperature range of a shrinking process of the compact; (B) increasing the temperature of the compact to a second temperature within a temperature range of a liquid phase sintering process of the compact after (A); (C) decreasing the temperature of the compact to a third temperature within the temperature range of the shrinking process of the compact after (B); and (D) retaining the third temperature after (C).

A solid electrolyte is made of zirconia grains containing yttria and alumina grains dispersed in the zirconia grains. In the solid electrolyte, the yttria content per zirconia content is within a range of 2 to 10 mol. %, the relative density is not less than 93%, and the average particle size Rz of the zirconia grains is not more than 2 m, an average particle size Ra of the alumina grains is not more than 1 m. The average particle size Ra of the alumina grains is smaller than the average particle size Rz of the zirconia grains. An average distance value A.sub.La between the alumina grains is not more than 2 m, and a standard deviation S.sub.La thereof is not more than 0.8. The solid electrolyte satisfies a relationship of (S.sub.La/A.sub.La)Rz0.9.

A transparent, tape casted, spinel article, as defined herein. Also disclosed is a method of method of making the tape casted, transparent spinel, and laminates of the tape casted. transparent spinel, as defined herein.

Provided is a lead-free piezoelectric ceramics having enhanced mechanical quality factor (Qm) and mechanical strength. The piezoelectric ceramics, includes at least a first crystal grain and a second crystal grain. The first crystal grain has an average equivalent circle diameter of 2 m or more and 30 m or less. The first crystal grain includes a perovskite-type metal oxide represented by the following general formula (1) as a main component, and the second crystal grain includes a perovskite-type metal oxide represented by the following general formula (2) as a main component: (1) xBaTiO.sub.3-yCaTiO.sub.3-zCaZrO.sub.3; and (2) xBaTiO.sub.3-yCaTiO.sub.3-zCaZrO.sub.3, provided that x, y, z, x, y, and z satisfy x+y+z=1, x+y+z=1, 0x0.15, 0.85y1, 0z0.05, x>x, 0<y<y, and z>0.

Disclosed herein are embodiments of modified z-type hexagonal ferrite materials having improved properties that are advantageous for radiofrequency applications, in particular high frequency ranges for antennas and other devices. Atomic substitution of strontium, aluminum, potassium, and trivalent ions can be used to replace certain atoms in the ferrite crystal structure to improve loss factor at high frequencies.

A barium titanate piezoelectric ceramic having good piezoelectric properties and mechanical strength and a piezoelectric element that includes the ceramic are provided. A method for making a piezoelectric ceramic includes forming a compact containing barium titanate particles, sintering the compact, and decreasing the temperature of the compact. The sintering includes (A) increasing the temperature of the compact to a temperature range of a shrinking process of the compact; (B) increasing the temperature of the compact to a temperature range of a liquid phase sintering process of the compact; (C) decreasing the temperature of the compact to the temperature range of the shrinking process of the compact; and (D) retaining the third temperature.