A sintered compact includes an alumina phase as a primary phase, and further includes an amorphous phase containing Si and Mn and a cordierite phase. The sintered compact has a porosity of higher than or equal to 1.1% and less than or equal to 5.0%. Preferably, I1/(I1+I2) is greater than or equal to 0.20 and less than or equal to 0.45, where I1 is the strength of the main peak of cordierite obtained by an XRD method, and I2 is the strength of the main peak of alumina.

Provided is a dielectric body having a high dielectric constant and a change rate of the dielectric constant of 30% or less, in a temperature range from −50° C. to 350° C.

An inorganic substance contains an oxide crystal including A and M (the A being one or more of P, Ge, and V, and the M being one or more of Nb and Ta), wherein the dielectric constant is 500 or more. In the inorganic substance, the oxide crystal is one or more of PNb.sub.9O.sub.25, P.sub.2.5Nb.sub.18O.sub.50 and GeNb.sub.9O.sub.25, GeNb.sub.18O.sub.47, GeNb.sub.19.144O.sub.50, VNb.sub.9O.sub.25, VNb.sub.9O.sub.24.9, PTa.sub.9O.sub.25, GeTa.sub.9O.sub.25, VTa.sub.9O.sub.25, and solid solutions thereof.

A method of manufacturing a winding assembly for an electrical machine, the method comprising: selecting (S1) a mathematical function defining the spatial separation between adjacent turns of a winding path, the mathematical function dependent on one or more parameters of the electrical machine and/or of the anticipated operating environment of the electrical machine; forming (S2), by three-dimensional, 3D, printing, an electrically insulating body comprising a channel defining the winding path in accordance with said function, the channel having an inlet and an outlet; heating (S3) the electrically insulating body to a temperature above the melting point of an electrically conducting material; flowing (S4) the electrically conducting material through the inlet to the outlet to fill the channel; and cooling the electrically insulating body to solidify the electrically conducting material within the channel, thereby forming said winding assembly.

A method of manufacturing a winding assembly for an electrical machine, the method comprising: selecting (S1) a mathematical function defining the spatial separation between adjacent turns of a winding path, the mathematical function dependent on one or more parameters of the electrical machine and/or of the anticipated operating environment of the electrical machine; forming (S2), by three-dimensional, 3D, printing, an electrically insulating body comprising a channel defining the winding path in accordance with said function, the channel having an inlet and an outlet; heating (S3) the electrically insulating body to a temperature above the melting point of an electrically conducting material; flowing (S4) the electrically conducting material through the inlet to the outlet to fill the channel; and cooling the electrically insulating body to solidify the electrically conducting material within the channel, thereby forming said winding assembly.

A cable includes an inner conductor; a dielectric arranged around the inner conductor; an outer conductor annularly arranged around the dielectric; a plurality of tapes around the outer conductor, each tape providing a successive layer over and circumferentially surrounding an underlying tape or the outer conductor, wherein one of the tapes is a conductor; and a jacket encasing the plurality of tapes.

A cable includes an inner conductor; a dielectric arranged around the inner conductor; an outer conductor annularly arranged around the dielectric; a plurality of tapes around the outer conductor, each tape providing a successive layer over and circumferentially surrounding an underlying tape or the outer conductor, wherein one of the tapes is a conductor; and a jacket encasing the plurality of tapes.

A spark plug insulator comprising a ceramic body with a photopolymerized and sintered microstructure. The spark plug insulator can have one or more complex geometries, such as dual axial bores, channels or grooves for wiring or the like, or internal wells. In one embodiment, an internal well is situated in the nose portion of the axial bore. The internal well has a terminal end, a base, and a ceramic bounding ring that is diametrically reduced with respect to a diameter at the base of the internal well. In some embodiments, there is a center electrode shield portion adjacent the internal well, where a diameter of the center electrode shield portion is diametrically reduced with respect to the diameter at the base of the internal well.

A spark plug insulator comprising a ceramic body with a photopolymerized and sintered microstructure. The spark plug insulator can have one or more complex geometries, such as dual axial bores, channels or grooves for wiring or the like, or internal wells. In one embodiment, an internal well is situated in the nose portion of the axial bore. The internal well has a terminal end, a base, and a ceramic bounding ring that is diametrically reduced with respect to a diameter at the base of the internal well. In some embodiments, there is a center electrode shield portion adjacent the internal well, where a diameter of the center electrode shield portion is diametrically reduced with respect to the diameter at the base of the internal well.

A temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material and a preparation method thereof are provided. Using ion doping modification to form solid solution structure is an important measure to adjust microwave dielectric properties, especially the temperature stability. Based on formation rules of the solid solution, ion replacement methods are designed including Ni.sup.2+ ions are replaced by Cu.sup.2+ ions, and (Ni.sub.1/3Ta.sub.2/3).sup.4+ composite ions are replaced by [(Al.sub.1/2Nb.sub.1/2).sub.ySn.sub.1-y].sup.4+ composite ions, which considers that cations with similar ionic radii to Ni.sup.2+ and Ta.sup.5+ ions can be introduced into the NiTa.sub.2O.sub.6 ceramic for doping under the same coordination environment (coordination number=6), and therefore a ceramic material with the NiTa.sub.2O.sub.6 solid solution structure can be obtained. The microwave dielectric ceramic material with excellent temperature stability and low loss is finally prepared by adjusting molar contents of each of doped ions, and its microwave dielectric properties are excellent.

A temperature-stable modified NiO—Ta.sub.2O.sub.5-based microwave dielectric ceramic material and a preparation method thereof are provided. Using ion doping modification to form solid solution structure is an important measure to adjust microwave dielectric properties, especially the temperature stability. Based on formation rules of the solid solution, ion replacement methods are designed including Ni.sup.2+ ions are replaced by Cu.sup.2+ ions, and (Ni.sub.1/3Ta.sub.2/3).sup.4+ composite ions are replaced by [(Al.sub.1/2Nb.sub.1/2).sub.ySn.sub.1-y].sup.4+ composite ions, which considers that cations with similar ionic radii to Ni.sup.2+ and Ta.sup.5+ ions can be introduced into the NiTa.sub.2O.sub.6 ceramic for doping under the same coordination environment (coordination number=6), and therefore a ceramic material with the NiTa.sub.2O.sub.6 solid solution structure can be obtained. The microwave dielectric ceramic material with excellent temperature stability and low loss is finally prepared by adjusting molar contents of each of doped ions, and its microwave dielectric properties are excellent.