Abstract: An opaque silica glass article comprising a transparent portion and an opaque portion, wherein the opaque portion has an apparent density of 1.70-2.15 g/cm3 and contains 5×104-5×106 bubbles per cm3, said bubbles having an average diameter of 10-100 &mgr;m; and the transparent portion has an apparent density of 2.19-2.21 g/cm3 and the amount of bubbles having a diameter of at least 100 &mgr;m in the transparent portion is not more than 1×103 per cm3.

Abstract: An opaque silica glass article comprising a transparent portion and an opaque portion, wherein the opaque portion has an apparent density of 1.70-2.15 g/cm3 and contains 5×104-5×106 bubbles per cm3, said bubbles having an average diameter of 10-100 &mgr;m; and the transparent portion has an apparent density of 2.19-2.21 g/cm3 and the amount of bubbles having a diameter of at least 100 &mgr;m in the transparent portion is not more than 1×103 per cm. The opaque silica glass article is made by a process wherein a mold is charged with a raw material for forming the opaque portion, which is a mixture comprising a silica powder with a small amount of a silicon nitride powder, and a raw material for forming the transparent portion so that the two raw materials are located in the positions corresponding to the opaque and the transparent portions, respectively, of the silica glass article to be produced; and the raw materials are heated in vacuo to be thereby vitrified.

Abstract: An opaque silica glass article comprising a transparent portion and an opaque portion, wherein the opaque portion has an apparent density of 1.70-2.15 g/cm3 and contains 5×104−5×106 bubbles per cm3, said bubbles having an averaged diameter of 10-100 &mgr;m; and the transparent portion has an apparent density of 2.19-2.21 g/cm3 and the amount of bubbles having a diameter of at least 100 &mgr;m in the transparent portion is not more than 1×103 per cm3. The opaque silica glass article is made by a process wherein a mold is charged with a raw material for forming the opaque portion, which is a mixture comprising a silica powder with a small amount of a silicon nitride powder, and a raw material for forming the transparent portion so that the two raw materials are located in the positions corresponding to the opaque and the transparent portions, respectively, of the silica glass article to be produced; and the raw materials are heated in vacuo to be thereby vitrified.

Abstract: Opaque quartz glass is provided which contains gas bubbles uniformly dispersed therein and is excellent in high-temperature viscosity and heat-insulating property. The opaque quartz glass has a defined apparent density, contains bubbles having a defined average bubble diameter in a defined amount, has a defined total bubble sectional area, generally exhibits a defined linear transmittance at a thickness of 1 mm or larger to projected light of a defined wavelength and contains nitrogen in a defined concentration. The opaque quartz glass is produced by a process comprising packing into a mold a powdery source material of powdery silica having a defined average particle diameter and powdery silicon nitride dispersed therein in a defined amount, heating the powdery source material to one of two first defined temperature ranges (both under vacuum) and further heating the source material up to a second temperature higher than the melting point and not higher than 1900.degree. C.

Abstract: The high-purity, opaque quartz glass containing 3.times.10.sup.6 -9.times.10.sup.6 of closed cells having an average size of 20-40 .mu.m per 1 cm.sup.3, a ratio of closed cells having sizes of 100 .mu.m or more to the whole of cells being 1% or less, thereby showing 5% or less of linear transmittance for near infrared rays (.lambda.=900 nm) at a thickness of 1 mm is produced by compacting amorphous silica powder having an average particle size of 0.5-10 .mu.m, in which each of impurities selected from Li, Na, K, Fe, Ti and Al is 1 ppm or less, if any, and sintering the resultant green body at 1730.degree.-1850.degree. C.

Abstract: A laminated silicon oxide film capacitor including a conductive or semiconductive silicon substrate and, formed on the substrate surface, at least one laminated film comprising a silicon oxide layer and an electrode layer laminated one on the other, and electrodes.

Abstract: A method of producing powder of lithium zirconate is disclosed, in which a gel-like zirconium compound obtained by hydrolyzing or neutralizing an aqueous solution of a zirconium salt is mixed with an aqueous solution of a lithium salt and the mixture is dehydrated, temporarily burned and pulverized.

Abstract: An actuator of the present invention is composed of a monomorph-type piezoelectric ceramic. The monomorph-type piezoelectric ceramic is a BaTiO.sub.3 -based ceramic, a PZT based ceramic having Nb, Sb, La, Mn, Nd and Bi, BaTiO.sub.3 --SrTiO.sub.3 -based ceramic containing SrTiO.sub.3 by 20 to 35 mole %, K(Nb, Ta)O.sub.3 -based ceramic, or a ceramic represented by a general formula: [Pb, (A.sub.1/2 B.sub.1/2)](Zr.sub.1-n, Cn)O.sub.3 where A is a monovalent element such as Li, Na, K, Rb, Cs or the like, B is a trivalent element such as Bi, La, Y, Sb, Ga or the like, A and B being both replaceable solid-meltable elements for Pb, C is an element such as Ti, Sn or the like that is a replaceable solid-meltable element for Zr, and n is from 0 to 0.8.