An oxide-based semiconductor compound including metal cations and oxygen, wherein hydride ions H.sup. originally bonded with the metal cations have been replaced with fluorine ions F.sup. and at least one of the fluorine ions F.sup. is bonded with one to three of the metal cations.

An oxide superconductor includes: REBa.sub.2Cu.sub.3O.sub.7-x (RE being one element selected from a RE element group of Pr, Nd, Sm, Eu, Gd, Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The RE includes at least three, types of metallic elements (M1, M2, and M3), and the three types of metallic elements are any element of the RE element group selected in order. In an oxide system satisfying R(1)20 mol % and R(M2)60 mol % and R(M3)20 mol %, R(M1) being an average metallic element ratio of M1 in M1+M2+M3, SD(Ms)>0.15 is satisfied at a position at 50% of an average film thickness of a cross section including the c-axis, Ms being the metallic element of not larger of R(M1) and R(M3), SD(Ms) being a standard deviation/average value of a concentration of Ms.

A sintered body includes a crystal grain containing silicon nitride, and a grain boundary phase. If dielectric losses of the sintered body are measured while applying an alternating voltage to the sintered body and continuously changing a frequency of the alternating voltage from 50 Hz to 1 MHz, an average value .sub.A of dielectric losses of the sintered body in a frequency band from 800 kHz to 1 MHz and an average value .sub.B of dielectric losses of the sintered body in a frequency band from 100 Hz to 200 Hz satisfy an expression |.sub.A.sub.B|0.1.

In an exemplary embodiment, a piezoelectric ceramic composition is an alkali niobate-based piezoelectric ceramic composition whose primary component is a compound expressed by the general formula Li.sub.xNa.sub.yK.sub.1xyNbO.sub.3 (where 0<x<1, 0<y<1, and x+y<1), and which contains 100 ppm or more but less than 1000 ppm of fluorine by mass. The alkali niobate-based piezoelectric ceramic composition demonstrates good properties even when sintered at low temperature.

The present invention relates to a light-transmitting ceramic sintered body which contains air voids having pore diameters of 1 m or more but less than 5 m at a density within the range of from 10 voids/mm.sup.3 to 4,000 voids/mm.sup.3 (inclusive), while having a closed porosity of from 0.01% by volume to 1.05% by volume (inclusive). With respect to this light-transmitting ceramic sintered body, a test piece having a thickness of 1.90 mm has an average transmittance of 70% or more in the visible spectrum wavelength range of 500-900 nm, and the test piece having a thickness of 1.90 mm has a sharpness of 60% or more at a comb width of 0.5 mm.

Disclosed herein are plasma chamber components that comprise a ceramic sintered body comprising at least one first layer comprising a surface having a surface area and at least one crystalline phase of from 90% to 99.8% by volume of poly crystalline yttrium aluminum garnet (YAG), at least one second layer comprising alumina and zirconia wherein the zirconia comprises at least one of stabilized and partially stabilized zirconia, and optionally, at least one third layer comprising at least one selected from the group consisting of YAG, alumina, and zirconia.

In an exemplary embodiment, a piezoelectric ceramic composition is an alkali niobate-based piezoelectric ceramic composition whose primary component is a compound expressed by the general formula Li.sub.xNa.sub.yK.sub.1-x-yNbO.sub.3 (where 0<x<1, 0<y<1, and x+y<1), and which contains 100 ppm or more but less than 1000 ppm of fluorine by mass. The alkali niobate-based piezoelectric ceramic composition demonstrates good properties even when sintered at low temperature.

An alumina sintered body of the present invention has a degree of c-plane orientation of 5% or more, which is determined by a Lotgering method using an X-ray diffraction profile in a range of 2=20 to 70 obtained under X-ray irradiation, and an XRC half width of 15.0 or less in rocking curve measurement, an F content of less than 0.99 mass ppm when measured by D-SIMS, a crystal grain diameter of 15 to 200 m, and 25 or less pores having a diameter of 0.2 m to 1.0 m when a photograph of a viewing area 370.0 m in a vertical direction and 372.0 m in a horizontal direction taken at a magnification factor of 1000 is visually observed.

A method for producing a transparent alumina sintered body includes (a) the step of preparing an alumina raw material powder containing a plate-like alumina powder having an aspect ratio of 3 or more so that the mass ratio R1 of F to Al in the alumina raw material powder is 5 ppm or more, and forming a compaction raw material containing the alumina raw material powder into a compact, and (b) the step of pressure-sintering the compact at a temperature at which F evaporate to yield a transparent alumina sintered body.

Disclosed is a multilayered capacitor including a capacitor body including a dielectric layer and an internal electrode and an external electrode disposed outside the capacitor body. The dielectric layer includes a plurality of dielectric crystal grains, the dielectric crystal grains include barium titanate as a main component and Dy.sub.2O.sub.3 as a subcomponent, and the barium titanate includes about 0.005 to about 0.065 wt % of Cl.