An insulator is rendered less breakable. A spark plug insulator is a tube-shaped spark plug insulator having a through hole extending in a direction of an axial line. The spark plug insulator contains alumina as a main component and mullite at at least part of the insulator. Mullite is contained in only an inner circumferential surface of the tube-shaped spark plug insulator and in at least part of the inner circumferential surface of the spark plug insulator in an area extending toward a distal end from a portion having a largest outer diameter.

An insulator is rendered less breakable. A spark plug insulator is a tube-shaped spark plug insulator having a through hole extending in a direction of an axial line. The spark plug insulator contains alumina as a main component and mullite at at least part of the insulator. Mullite is contained in only an inner circumferential surface of the tube-shaped spark plug insulator and in at least part of the inner circumferential surface of the spark plug insulator in an area extending toward a distal end from a portion having a largest outer diameter.

A dielectric ceramic composition and a multilayer ceramic capacitor comprising the same includes a barium titanate (BaTiO.sub.3)-based base material main ingredient and an accessory ingredient, and the accessory ingredient includes a third trivalent lanthanide rare earth element A and terbium (Tb) as rare earth elements, and a molar ratio (Tb/A) of a content of terbium (Tb) to the content of the trivalent lanthanide rare earth element A satisfies 0.15≤Tb/A<0.50.

A dielectric ceramic composition and a multilayer ceramic capacitor comprising the same includes a barium titanate (BaTiO.sub.3)-based base material main ingredient and an accessory ingredient, and the accessory ingredient includes a third trivalent lanthanide rare earth element A and terbium (Tb) as rare earth elements, and a molar ratio (Tb/A) of a content of terbium (Tb) to the content of the trivalent lanthanide rare earth element A satisfies 0.15≤Tb/A<0.50.

Polymer-ceramic composite articles with relatively low dissipation factor (Df) and relatively high dielectric constant (Dk), as well as polymer-ceramic core-shell powders and pellets adapted for making such composite articles. The ceramic-polymer composites, in powder and/or pellet forms, comprise a plurality of core-shell particles, where: each of the core-shell particles comprises a core and a shell around the core; the core comprises a ceramic that is selected from the group of ceramics consisting of: BaTiO.sub.3, SrTiO.sub.3, TiO.sub.2, CaTiO.sub.3, MgTiO.sub.3, and combinations of any two or more thereof; and the shell comprises a polymer selected from the group of polymers consisting of: polyetherimide (PEI), polyetherimide (PEI) copolymers, polyphenylene ether (PPE), polyphenylene sulfide (PPS), polyaryl ether ketone (PAEK), polypropylene (PP), polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), fluorinated ethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), and ethylene chlorotrifluoroethylene (ECTFE). The core-shell particles can be in a powder form (e.g., a dry powder). In pellet form, shells of adjacent core-shell particles are joined to resist separation of the adjacent core-shell particles and deformation of a respective pellet. Methods of forming a ceramic-polymer composite comprise: superheating a mixture of the polymer (PEI, PEI copolymers, PPE, PPS, PAEK, PP, PTFE, PFA, FEP, ETFE, PVDF, and/or ECTFE), solvent, and the ceramic (BaTiO.sub.3, SrTiO.sub.3, TiO.sub.2, CaTiO.sub.3, and/or MgTiO.sub.3), to dissolve the polymer in the solvent; agitating the superheated mixture while substantially maintaining the mixture at an elevated temperature and pressure; and cooling the mixture to cause the polymer to precipitate on the particles of the ceramic and thereby form a plurality of the present polymer-ceramic core-shell particles. Methods of molding a part comprise subjecting a powder or pellets of the present polymer-ceramic core-shell particles that substantially fills a mold to a first pressure while the powder is at or above a first temperature above a glass transition temperature (T.sub.g) or if no T.sub.g then above a melting temperature (T.sub.m) of the polymers.

A gap sub assembly for electromagnetic telemetry used in downhole drilling is disclosed. The gap sub comprises a female part comprising a female mating section and a male part comprising a male mating section. The male mating section is matingly received within the female mating section and electrically isolated therefrom. One or more electrically insulating bodies secure the male part axially and torsionally relative to the female part. The electrically insulating bodies also electrically isolate the male part from the female part. The electrically insulating bodies can be installed through apertures in the female part or at least some of the electrically insulating bodies can be installed before the male mating section is inserted into the female mating section. The electrically insulating bodies can be held in place on the male mating section using a retention apparatus such as a ring, a scarf, pods or an adhesive.

A gap sub assembly for electromagnetic telemetry used in downhole drilling is disclosed. The gap sub comprises a female part comprising a female mating section and a male part comprising a male mating section. The male mating section is matingly received within the female mating section and electrically isolated therefrom. One or more electrically insulating bodies secure the male part axially and torsionally relative to the female part. The electrically insulating bodies also electrically isolate the male part from the female part. The electrically insulating bodies can be installed through apertures in the female part or at least some of the electrically insulating bodies can be installed before the male mating section is inserted into the female mating section. The electrically insulating bodies can be held in place on the male mating section using a retention apparatus such as a ring, a scarf, pods or an adhesive.

Elastomer compositions with high dielectric constants are disclosed. Embodiments of the disclosure include a high dielectric constant (high-K) elastomeric composition comprising an elastomer, carbon black (CB), and organoclay (OC). The composition is not dependent on any raw material with inherent high-k or any metal oxide type material that changes conductivity with applied voltages. The composition instead uses distributed electric fields and polarizability with carbon black and organoclays. This allows for a high-k material through polarizability with limited large-scale electron sharing.

Elastomer compositions with high dielectric constants are disclosed. Embodiments of the disclosure include a high dielectric constant (high-K) elastomeric composition comprising an elastomer, carbon black (CB), and organoclay (OC). The composition is not dependent on any raw material with inherent high-k or any metal oxide type material that changes conductivity with applied voltages. The composition instead uses distributed electric fields and polarizability with carbon black and organoclays. This allows for a high-k material through polarizability with limited large-scale electron sharing.

A conductor assembly including an electrically conductive material defining a longitudinal axis, a microporous membrane surrounding the electrically conductive material defining a series of pores, and a ceramic material within at least a first portion of the series of pores.