Disclosed herein is a dual density disc comprising a dense outer tube comprising alumina having a purity of greater than 99%; and a porous core comprising alumina of a lower density than a density of the dense outer tube; wherein the porous core has an alumina purity of greater than 99%. Disclosed herein too is method comprising disposing in a dense outer tube a slurry comprising alumina powder and a pore former; heating the dense outer tube with the slurry disposed therein to a temperature of 300 to 600° C. to activate the pore former; creating a porous core in the dense outer tube; and sintering the dense outer tube with the porous core at a temperature of 800 to 2000° C. in one or more stages.

Provided is a dielectric composition containing: a main component expressed by {Ba.sub.xSr.sub.(1-x)}.sub.mTa.sub.4O.sub.12; and a first subcomponent, m satisfying a relationship of 1.95≤m≤2.40. The first subcomponent includes silicon and manganese. When the amount of the main component contained in the dielectric composition is set to 100 parts by mole, the amount of silicon contained in the dielectric composition is 5.0 to 20.0 parts by mole in terms of SiO.sub.2, and the amount of manganese contained in the dielectric composition is 1.0 to 4.5 parts by mole in terms of MnO.

A dielectric composition includes a main ingredient having a perovskite structure represented by ABO.sub.3, where A is at least one of Ba, Sr, and Ca and B is at least one of Ti, Zr, and Hf, and a first accessory ingredient. The first accessory ingredient comprises 0.1 mole or more of a rare earth element, 0.02 mole or more of Nb, and 0.25 mole or more and 0.9 mole or less of Mg, a sum of contents of the rare earth element and Nb is 1.5 mole or less.

A capacitor includes a stack and an external electrode located on a surface of the stack. The stack includes a plurality of dielectric layers and a plurality of internal electrode layers alternately stacked on one another. Crystal grains include first crystal grains having a small grain size and second crystal grains having a larger grain size. The first crystal grains satisfy 0.13 μm≤d1<0.30 μm, where d1 is the grain size of the first crystal grains. The second crystal grains satisfy 0.30 μm≤d2<0.50 μm, where d2 is the grain size of the second crystal grains. The second crystal grains have a higher additive element content than the first crystal grains.

A cubic boron nitride sintered body including cubic boron nitride and a binder phase, wherein a content of the cubic boron nitride is 40 volume % or more and 80 volume % or less; a content of the binder phase is 20 volume % or more and 60 volume % or less; an average particle size of the cubic boron nitride is 0.5 μm or more and 4.0 μm or less; the binder phase contains TiC and TiB.sub.2 and contains substantially no AlN and/or Al.sub.2O.sub.3; a (101) plane of TiB.sub.2 in the binder phase shows a maximum peak position (2θ) in X-ray diffraction of 44.2° or more; and a (200) plane of TiC in the binder phase shows a maximum peak position (2θ) in X-ray diffraction of less than 42.1°.

A ceramic composition is provided. The ceramic composition includes a corundum phase, and a CeAl.sub.11O.sub.18 phase. A ratio of an amount of substance of the CeAl.sub.11O.sub.18 phase with respect to a total amount of substance of the ceramic composition is not lower than 0.5 mol % and not higher than 5 mol %.

An exemplary embodiment of the present disclosure provides a method for manufacturing a transparent ceramic material. The method comprises providing a compact comprising a metal oxide and, during sintering, exposing the compact to a vapor comprising one of or both fluorine ions and lithium ions to form a transparent ceramic material comprising at least 90% of a theoretical transparency.

A dielectric material which satisfies X9M characteristics and ensures operations over an extended period of time at 200° C. is provided.

A dielectric composition includes a main phase and a Ca—Si—P—O segregation phase. The main phase includes a main component expressed by ABO.sub.3. “A” includes at least one selected from calcium and strontium. “B” includes at least one selected from zirconium, titanium, hafnium, and manganese. The Ca—Si—P—O segregation phase includes at least calcium, silicon, and phosphorus.

A composite precursor powder, including one or more metals or metalloids, and one or more oxides, wherein a molar ratio of the one or more metals or metalloids to the one or more oxides is from about 1:0.01 to about 1:4, and wherein the molar ratio of the one or more metals or metalloids to the one or more oxides is configured according to a desired volumetric change of the composite precursor powder when converted to a non-oxide ceramic.